Dr. Jeff Masters' WunderBlog

Great Lakes ice cover down 71% since 1973

By: JeffMasters, 1:08 PM GMT en Marzo 30, 2012

Ice cover on North America's Great Lakes--Superior, Michigan, Huron, Ontario, and Erie--has declined 71% since 1973, says a new study published in the Journal of Climate by researchers at NOAA's Great Lakes Environmental Research Laboratory. The biggest loser of ice during the 1973 - 2010 time period was Lake Ontario, which saw an 88% decline in ice cover. During the same time period, Superior lost 79% of its ice, Michigan lost 77%, Huron lost 62%, and Erie lost 50%. The loss of ice is due to warming of the lake waters. Winter air temperatures over the lower Great Lake increased by about 2.7°F (1.5°C) from 1973 - 2010, and by 4 - 5°F (2.3 - 2.7°C) over the northern Lakes, including Lake Superior. Lake Superior's summer surface water temperature warmed 4.5°F (2.5°C) over the period 1979 - 2006 (Austin and Colman 2007). During the same period, Lake Michigan warmed by about 3.3°F (1.7°C), Lake Huron by 4.3°F (2.4°C), and Lake Erie showed almost no warming. The amount of warming of the waters in Lakes Superior, Huron, and Michigan is higher than one might expect, because of a process called the ice-albedo feedback: when ice melts, it exposes darker water, which absorbs more sunlight, warming the water, forcing even more ice to melt. This sort of vicious cycle is also responsible for the recent extreme loss of Arctic sea ice. The increase in temperature of the lakes could be due to a combination of global warming and natural cycles, the researchers said. They noted a pronounced 4-year and 8-year oscillation in ice coverage, which could be caused by the El Niño/La Niña and Arctic Oscillation (AO), respectively.

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Figure 1. A tale of two winters: Lake Superior was choked with ice at the end of the winter of 2008 - 2009 (top), but was virtually ice-free at the end of the winter of 2011 - 2012 (bottom.) Image credit: NASA.

The consequences of Great Lakes ice loss
Ice coverage on the Great Lakes was just 5% this past winter, the second lowest on record, behind 2002. The lack of Great Lakes ice this winter probably added a few degrees of warmth to the unprecedented "Summer in March" conditions observed in Michigan last week--an event the National Weather Service in Detroit called "perhaps the most anomalous weather event in Michigan since climate records began 130 years ago." We can anticipate that areas surrounding the Great Lakes will see an increased incidence of warm spring weather due to decreased ice cover on the lakes.

The loss of Great Lakes ice has allowed much more water to evaporate in winter, resulting in heavier lake effect snow near the shore, and lower lake levels. Lower water levels have had a significant impact on the Great Lakes economy. Over 200 million tons of cargo are shipped every year through the Great Lakes. Since 1998, when water levels took a severe drop, commercial ships were forced to light-load their vessels. For every inch of clearance that these oceangoing vessels lost because of low water levels, $11,000 - $22,000 in profits were lost per day. Hydropower plants have also been affected by low water levels; several New York and Michigan plants were run at reduced capacity, forcing them to buy higher priced energy from other sources, and passing on the higher costs to consumers. The large loss of ice is also likely to accelerate shoreline erosion because of the increase in open water, and promote more algal blooms. It is uncertain if the Great Lake water levels will continue to fall as the climate warms, since the region is expected to see an increase in precipitation over the coming decades. In Michigan, annual precipitation increased by about 14% between 1895 - 2011, according to the National Climatic Data Center.


Figure 2. Great Lakes ice coverage for the period December 4 - March 5, from the winter of 1980 - 1981 through 2011 - 2012. The winter of 2011 - 2012 had the second lowest ice coverage on record, just 5%. Only 2001 - 2002 (4.5%) had lower ice cover. The median ice coverage between 1980 - 2011 was about 19%. Image credit: Environment Canada.


Figure 3. Water levels on Lake Superior between 1860 and February 2012. Since the late 1990s, water levels have seen a steep decline, due to the loss of ice cover allowing more evaporation. Image credit: NOAA/GLERL.

References
Austin, J. A., and S. Colman, 2007, "Lake Superior summer water temperatures are increasing more rapidly than regional air temperatures: A positive ice-albedo feedback," Geophys. Res. Lett., 34, L06604, doi:10.1029/2006GL029021.

Wang, J., X. Bai, H. Hu, A.H. Clites, M.C. Colton, and B.M. Lofgren, 2012, "Temporal and spatial variability of Great Lakes ice cover, 1973-2010," Journal of Climate 25(4):1318-1329 (DOI:10.1175/2011JCLI4066.1)

Have a great weekend, everyone! I'll be back by Monday at the latest with a new post, and may post some weather humor on Sunday (April Fools Day), as well.

Jeff Masters

Winter Weather Climate Change

Updated: 1:19 AM GMT en Diciembre 15, 2012

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February 2012 the globe's 22nd warmest; record Hawaii hailstone confirmed

By: JeffMasters, 2:09 PM GMT en Marzo 28, 2012

February 2012 was the globe's 22nd warmest February on record, according to the National Oceanic and Atmospheric Administration's National Climatic Data Center (NCDC). Global temperatures were the 15th warmest on record according to NASA. It was the coolest February since 1994, and the coolest month, relative to average, since January 2008. The relatively cool temperatures were due, in part, to the on-going La Niña event in the Eastern Pacific, which has brought a large amount of cool water to the surface. February 2012 global land temperatures were the 37th warmest on record, and ocean temperatures were the 12th warmest on record. Global satellite-measured temperatures for the lowest 8 km of the atmosphere were colder than average, the 7th or 13th coldest in the 34-year record, according to Remote Sensing Systems and the University of Alabama Huntsville (UAH). February temperatures in the stratosphere were the coldest on record. We expect cold temperatures there due to the greenhouse effect and to destruction of ozone due to CFC pollution. Snow cover during February varied dramatically depending on which hemisphere you were in. Eurasia had its third largest snow cover extent in the 46-year period of record, while North America had its fourth lowest. As seen in Figure 1, much of North America and Siberia were much warmer than average, while Europe was considerably colder than average. Wunderground's weather historian, Christopher C. Burt, has a comprehensive post on the notable weather events of February in his February 2012 Global Weather Extremes Summary.


Figure 1. Departure of temperature from average for February 2012. Image credit: National Climatic Data Center (NCDC) .

La Niña weakens, almost gone
A borderline weak La Niña event continues in the equatorial Pacific, where sea surface temperatures were approximately 0.5°C below average during February and the the first half of March. NOAA's Climate Prediction Center forecasts that La Niña will be gone by the end of April. The majority of the El Niño computer models predict neutral conditions for this fall, during the August - September - October peak of hurricane season, though 32% of the models predict an El Niño will develop. El Niño conditions tend to decrease Atlantic hurricane activity, by increasing wind shear over the tropical Atlantic.

February Arctic sea ice extent fifth lowest on record
Arctic sea ice extent was at its fifth lowest extent on record in February, according to the National Snow and Ice Data Center. Continuing the pattern established in January, conditions differed greatly between the Atlantic and Pacific sides of the Arctic. On the Atlantic side, especially in the Barents Sea, air temperatures were higher than average and ice extent was unusually low. February ice extent for the Barents Sea was the lowest in the satellite record, due to air temperatures that ranged from 4 - 8°C (7 - 14°F) above average at the 925 mb level (about 3000 feet above sea level). In contrast, on the Pacific side, February ice extent in the Bering Sea was the second highest in the satellite record, paired with air temperatures that were 3 to 5 degrees Celsius (5 to 9 degrees Fahrenheit) below average at the 925 mb level. Satellite sea ice records date back to 1979.


Figure 2. Record-setting hailstone from the Hawaii 'supercell' thunderstorm that hit the Hawaiian island of Oahu on March 9, 2012. Image credit: NOAA/National Weather Service.

Huge hailstone sets Hawaii record
A hailstone with the diameter of roughly that of a grapefruit that hit Oahu on March 9, 2012, has been confirmed as the largest hailstone on record for the state of Hawaii, according to NOAA. The record-setting hailstone was dropped by a “supercell” thunderstorm on the windward side of Oahu. There were numerous reports of hail with diameters of 2 to 3 inches and greater. Hail the size of a penny (diameter of 3/4 inch) or quarter (diameter of one inch) has been reported in Hawaii only eight times since records began, and there is no record of hail larger than 1 inch in diameter. Hail the size of golf balls and baseballs can only form within intense thunderstorms called supercells. These supercells need warm, moist air to rise into progressively colder, drier air, as well as winds changing direction and increasing speed with increasing height off the ground. For both sets of conditions to exist at the same time in Hawaii is extremely rare, but that did occur on March 9. Conditions that day were ideal for a supercell to form, and the storm looked very much like supercell thunderstorms common in the Central U.S. during spring. Supercells can also produce tornadoes, another rarity in Hawaii. The same hail-producing supercell produced a confirmed EF-0 tornado with winds of 60-70 mph in Lanikai and Enchanted Lakes on Oahu.

Jeff Masters

Climate Summaries Severe Weather

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Hard freeze hits Midwest and Northeast fruit trees

By: JeffMasters, 2:36 PM GMT en Marzo 27, 2012

Large portions of Michigan, Ohio, and Pennsylvania shivered through a hard freeze (temperatures below 28°F ) this morning, and cold temperatures will cause widespread damage to flowering plants fooled into blooming by last week's unprecedented "Summer in March" heat wave. Growers of apples, pears, peaches, nectarines, plums, and cherries worked during the night and early morning to minimize the damage by running large fans and propane heaters in their orchards in an attempts to keep temperatures a few degrees warmer. While freezing temperatures for an extended period will not kill the trees, they will destroy the flowers and fragile buds that are needed to produce fruit later in the year. I expect that this morning's freeze was severe and widespread enough to cause tens of millions of dollars in damage to the fruit industry, but it will be several weeks before the extent of the damage is known. It would take several nights of temperatures in the 20s to cause a more significant billion-dollar disaster, such as occurred in 2007. A warm spell in March that year was followed by cold temperatures in early April that were 10 - 20 degrees below average, bringing killing frosts and freezes to the Midwest and South that caused $2.2 billion in agricultural damage, wiping out apple, peach, winter wheat and alfalfa crops.

During the remainder of this week, temperatures are expected to be much warmer than they were this morning, so the freeze damage will be limited compared to 2007. However, we still have two more months to go this spring when temperatures commonly fall below freezing. Plants will steadily grow more susceptible to cold temperatures in the coming weeks as the growing season progresses, and the odds of more destructive frosts and freezes for the Midwest and Northeast fruit industry are high.


Figure 1. Low temperatures this morning dipped below 30 degrees over Eastern Michigan, Northeast Ohio, Northern West Virginia, and much of Pennsylvania, in regions where spring bloom was well-advanced due to last week's record "Summer in March" heat wave. Widespread agricultural damage likely occurred in these areas.

History of billion-dollar U.S. freezes
Freezes can cause big damage to agriculture. According to NOAA's National Climatic Data Center, there have been six billion-dollar U.S. freezes since 1980, accounting for 5% of all billion-dollar weather-related disasters. Five of these freezes affected California or Florida; one hit the Midwest. Ranked by damages (in 2011 dollars), here are the six billion-dollar U.S. freeze events since 1980:

1) California Freeze of December 1990. Severe freeze in the Central and Southern San Joaquin Valley caused the loss of citrus, avocado trees, and other crops in many areas. Several days of subfreezing temperatures occurred, with some valley locations in the teens. $5.9 billion in direct and indirect economic losses, including damage to public buildings, utilities, crops, and residences.

2) Florida Freeze of December 1983. Severe freeze central/northern Florida; about $4.5 billion damage to citrus industry.

3) California Freeze of December 1998. A severe freeze damaged fruit and vegetable crops in the Central and Southern San Joaquin Valley. Extended intervals of sub 27° F temperatures occurred over an 8-day period; $3.5 billion estimated damages/costs.

4) Florida Freeze of January 1985. Severe freeze in central/northern Florida; about $2.5 billion damage to citrus industry.

5) East/Midwest freeze of April 2007. Widespread severe freeze over much of the East and Midwest (AL, AR, GA, IL, IN, IA, KS, KY, MS, MO, NE, NC, OH, OK, SC, TN, VA, WV), causing significant losses in fruit crops, field crops (especially wheat), and the ornamental industry. Temperatures in the teens/20's accompanied by rather high winds nullified typical crop-protection systems. Over $2.2 billion in damage/costs.

6) California Freeze of January 2007. For nearly two weeks in January, overnight temperatures over a good portion of California dipped into the 20's, destroying numerous agricultural crops, with citrus, berry, and vegetable crops most affected. $1.5 billion estimated in damage/costs; 1 fatality reported.

Scotland records its all-time warmest March temperature
The ridge of high pressure that brought "Summer in March" to the U.S. last week moved over Western Europe over the weekend, bringing sunny skies and record-breaking high temperatures to the U.K. Scotland broke its record for hottest March temperature on record on Sunday, when the mercury hit 22.8°C at Fyvie Castle, Aberdeenshire. The record lasted only one day, as a new high of 22.9°C was recorded in Aboyne, Aberdeenshire, on Monday. That record also lasted just one day, as Aboyne, Aberdeenshire has hit 23.4°C today. The previous March record in Scotland was 22.2°C at Gordon Castle (Morayshire) in March 1957, and at Strachan (Kincardineshire) in March 1965.

Canada's 1926 all-time March temperature record questioned
I reported last week that the 29.2°C (85°F) measured at Western Head, Nova Scotia on March 22, 2012 was the third warmest temperature ever recorded in Canada in March. Environment Canada lists the hottest March temperature as a 31.1°C at Beaver Creek on Vancouver Island, BC on March 29th, 1926. However, weather records researcher Maximiliano Herrera has looked into this record, and concluded that it is likely bogus. A station just a few miles away at Port Alberni measured a much cooler high temperature of 23.3°C that day, and the temperature range between the high and low temperature at Beaver Creek was almost 30°C, which is far too great for a station so close to the ocean. Such large differences between min and max temperature on sunny days usually commonly imply poor siting of the temperature instrument. He maintains that the highest March temperature in Canada should be the 29.4°C in 1921 at Wallaceburg, with the second highest being the 29.2°C (85°F) measured at Western Head, Nova Scotia on March 22, 2012.

Jeff Masters

Heat Winter Weather

Updated: 11:57 PM GMT en Marzo 27, 2012

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Hard freeze likely to significantly damage Midwest fruit trees

By: JeffMasters, 1:13 PM GMT en Marzo 26, 2012

After a week of temperatures in the 70s and 80s last week, it was a rude awakening for Michigan this morning, as temperatures across all but the extreme southern portions of the state dropped below freezing. Tonight, far colder temperatures in the low to mid-20s are expected across the entire state, and frosts and freezes are also expected in all of Ohio, plus portions of Indiana, Kentucky, Wisconsin, West Virginia, Virginia, Pennsylvania, Delaware, North Carolina, Maryland, Washington D.C., and New Jersey. A hard freeze (temperatures below 28°F ) will cause widespread damage to flowering plants fooled into blooming by last week's unprecedented "Summer in March" heat wave. Temperatures as hot as 90° hit Michigan last week, and the National Weather Service in Detroit called the "Summer in March" heat wave "perhaps the most anomalous weather event in Michigan since climate records began 130 years ago."


Figure 1. Frost and freeze advisories (white colors) are posted today for all of Lower Michigan and all of Ohio, plus portions of Indiana, Kentucky, Wisconsin, West Virginia, Virginia, Maryland, Pennsylvania, Delaware, North Carolina, Washington D.C., and New Jersey. Although freezing temperatures in the extreme Northeast are also expected, the growing season there has not yet begun, since last week's heat was not long-enough lived in that part of the country. Image taken from wunderground's severe weather map.

Fruit trees at risk
Tonight's hard freeze poses a significant danger to the region's fruit industry, and growers of apples, pears, peaches, nectarines, plums, and cherries are gearing up to battle the freezing temperatures by operating large fans and propane heaters in orchards in an attempts to keep temperatures a few degrees warmer. While freezing temperatures for an extended period will not kill the trees, they will destroy the flowers and fragile buds that are needed to produce fruit later in the year. The situation this week is similar to what occurred in 2007. A warm spell in March that year was followed by cold temperatures in early April that were 10 - 20 degrees below average, bringing killing frosts and freezes to the Midwest and South that caused $2.2 billion in agricultural damage, wiping out apple, peach, winter wheat and alfalfa crops. In an interview with citizensvoice.com, Ian Merwin, Ph.D., a horticulturist who specializes in tree fruit at Cornell University in Ithaca, N.Y., said, "I'm pretty sure this will be the earliest bloom, going back at least to the early 1900s. We are definitely in a very risky situation right now for the fruit crop in the whole Northeast."

Jeff Masters

Winter Weather Heat

Updated: 7:54 PM GMT en Marzo 26, 2012

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Summer in March, 2012, draws to a close

By: JeffMasters, 4:54 PM GMT en Marzo 23, 2012

The most incredible spring heat wave in U.S. and Canadian recorded history is finally drawing to a close today, after a ten-day stretch of unprecedented record-smashing intensity. Since record keeping began in the late 1800s, there have never been so many spring temperature records broken, and by such a large margin. Airports in fifteen different states have set all-time records for March warmth, which is truly extraordinary considering that the records were set in the middle of the month, instead of the end of the month. The 29.2°C (85°F) measured at Western Head, Nova Scotia yesterday was the third warmest temperature ever recorded in Canada in March, according to Environment Canada and weather records researcher Maximiliano Herrera (top two records: 31.1°C at Alberini Beaver Creek BC on March 29th 1926, and 29.4°C in 1921 at Wallaceburg.) Michigan's all-time record for March warmth was toppled on Wednesday, when the mercury hit 90°F at Lapeer. The previous record, 89° at Lapeer in 1910, was matched at three stations yesterday--Ypsilanti, Dearborn, and Lapeer. The duration, areal size, and intensity of the Summer in March, 2012 heat wave are simply off-scale, and the event ranks as one of North America's most extraordinary weather events in recorded history. Such a historic event is difficult to summarize, and in today's post I will offer just a few of the most notable highlights.


Figure 1. Clear skies over the Eastern U.S. caused by a blocking ridge of high pressure on March 21, 2012, are apparent in this visible satellite image. The comma-shaped cloud pattern over the Central U.S. is associated with a "cut-off" low pressure system. This low is moving over the Eastern U.S. today through Saturday, and will bring an end to "Summer in March" over the U.S. and Canada. Image credit: NOAA's Environmental Visualization Lab, and modified by Andrew Freedman of Climate Central.

Low temperatures beating previous high temperature records for the date
I've never seen a case where the low temperature for the date beat the previous record high. This happened on at least four occasions during "Summer in March, 2012":

The low temperature at Marquette, Michigan hit 52° on March 21, which was 3° warmer than the previous record high for the date.

The low at Mt. Washington, NH on March 21 (44°) beat the previous record high for the date (43°.)

The low temperature for International Falls, Minnesota on March 20 bottomed out at 60°F, tying the previous record high for the date.

The low temperature in Rochester, Minnesota on March 18 was 62°F, which beat the previous record high for the date of 60°.

Breaking all-time April records for warmth in March
Not only did many locations in Canada set records for their all-time warmest March day during "Summer in March, 2012", a number also broke their record for warmest April day:

St. John, New Brunswick hit 27.2°C (81°F) on March 21. Previous March record: 17.5°C on March 21, 1994. April record: 22.8°C.

Kejimkujik Park, Nova Scotia hit 27.9°C on March 21. Previous March record: 22.5°C on March 30, 1986. April record: 25°C on April 27, 1990.

Yesterday, I reported that Halifax, Nova Scotia hit 27.2°C (81°F) on March 22, 2012. Previous March record: 25.8° set the previous day. April record: 26.3°C, set on April 30, 2004. However, Rob Paola, a meteorologist with Environment Canada's Prairie and Arctic Storm Prediction Center in Winnipeg, Manitoba, wrote to tell me that Halifax did not break its April record: In fact, Halifax recorded a temperature of 29.5°C on April 28, 2009. For some reason, that stat does not show up on EC's normal/extremes climate site for Halifax, which only has data up to 2006 for extremes. More details on my blog at http://robsobsblog.blogspot.ca/

Breaking daily temperature records by more than 30°F
It is exceptionally rare for a weather station with a 50+ year period of record to break a daily temperature record by more than 10°F. During "Summer in March, 2012", beating daily records by 10° - 20°F was commonplace, and many records were smashed by over 20°. Two stations broke records by more than 30°F, which is truly surreal. Western Head, Nova Scotia hit 29.2°C (85°F), yesterday, breaking their previous record for the date (10.6°C in 1969) by 18.6°C (33°F.) Yesterday's high temperature was 24°C (44°F) above average. Pellston, Michigan in the Northern Lower Peninsula--dubbed "Michigan's Icebox", since it frequently records the coldest temperatures in the state--hit 85° on March 21. This broke the previous record for the date (53° in 2007) by 32°, and was an absurd 48°F above average.

Breaking daily temperature records nine consecutive days or more
It is extremely rare for stations with a 50+ year period of record to break a daily high temperature record for seven or more days in a row. The longest such streak of consecutive high temperature records at International Falls, Minnesota, was a 5-day period March 3 - 7, 2000. The city has tied or broken their high temperature for the date ten consecutive days, as of yesterday. This streak will likely end today, as the high is predicted to be 60 - 65, and the record high for the date is 66. Chicago, Illinois has tied or broken their daily high temperature record the past nine days in a row. This ties the nine-day streak of record highs set on August 26 - September 3, 1953. Other cites that have set daily high temperature records the past nine days in a row include Fort Wayne and South Bend, Indiana. Numerous cities have broken high temperature records on seven consecutive days during "Summer in March, 2012", including Gaylord, Pellston, and Traverse City in Michigan.


Figure 2. All-time high temperature records set in March 2012 for the U.S. The grey icons show locations where the March record was broken on multiple days. Image taken from wunderground's new record extremes page, using data from NOAA's National Climatic Data Center.

The big picture: the impacts of "Summer in March, 2012"
I've always said living in Michigan would be much more bearable if we could just get rid of March. March weather here is always horrible, with brutal cold, high winds, damaging ice storms, heavy snow, interminable cloudy stretches with no sun, all interspersed with a few teasing warm spells. Well, this year, I got my wish. This March, we started with twelve days of April weather, followed by ten days of June and July weather, with nine days of May weather predicted to round out the month. This has been a huge benefit to the economy--vastly reduced heating costs, no snow removal bills, and far fewer traffic accidents due to icy roads. However, there is major downside to the "Summer in March, 2012" heat wave. The growing season is now in full swing, five weeks early. A damaging freeze that will severely impact the fruit industry and other sensitive plants is very likely. Indeed, the forecast calls for lows in the upper 20s in the cherry-growing region of Michigan near Traverse City on Monday night. The exceptional March warmth has also melted all the snow in the northern U.S. and southern Canada, drying out the soils and setting the stage for a much warmer than average summer, and an increased chance of damaging drought conditions. The early loss of snowpack will also likely cause very low flow rates in the major rivers in late summer and early fall, reducing the amount of water needed for irrigation of crops. Low flows may also cause problems for navigation, limiting commercial barge traffic on Midwest rivers.

Links
Andrew Freedman of Climate Central interviewed a number of climate scientists who are experts in studying the link between extreme weather events and climate change for his post, Global Warming May Have Fueled March Heat Wave Odds.

Wunderground's weather historian Christopher C. Burt will be posting a more comprehensive summary of the "Summer in March, 2012" heat wave this weekend.

Have a great weekend, everyone, and I'll be back Monday with a new post. I expect I'll be hard at work this weekend, mowing my lawn for the first time ever in March!

Jeff Masters

Heat Extreme Weather

Updated: 2:06 PM GMT en Marzo 27, 2012

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Summer in March peaks in U.S. and Canada; record late snow in Oregon

By: JeffMasters, 1:17 PM GMT en Marzo 22, 2012

A spring heat wave like no other in U.S. and Canadian history peaked in intensity yesterday, during its tenth day. Since record keeping began in the late 1800s, there have never been so many temperature records broken for spring warmth in a one-week period--and the margins by which some of the records were broken yesterday were truly astonishing. Wunderground's weather historian, Christopher C. Burt, commented to me yesterday, "it's almost like science fiction at this point." A few of the more remarkable records from yesterday:

Pellston, MI: record high broken by 32°F
Pellston, Michigan in the Northern Lower Peninsula is called "Michigan's Icebox", since it frequently records the coldest temperatures in the state, and in the entire nation. But the past five days, Pellston has set five consecutive records for hottest March day. Yesterday's 85° reading broke the previous record for the date (53° in 2007) by a ridiculous 32°, and was an absurd 48°F above average.

Low temperatures beat the previous record high for the date at two stations
The low temperature at Marquette, Michigan was 52° yesterday, which was 3° warmer than the previous record high for the date! The low at Mt. Washington, NH yesterday (44°) also beat the previous record high for the date (43°.)

Canadian cities break all-time April record for warmth in March
Not only was yesterday the warmest March day in recorded history for many of Canada's major cities, it was also warmer than any April day at St. John, New Brunswick. The city hit 25.4°C (78°F.) Not only did this crush the record high for March (previous record: 17.5°C), it is well above any temperature ever measured in April (extreme April temperature on record: 22.8°C.) Halifax, Nova Scotia hit 25.8°C yesterday, beating their all-time March record of 25.6°, and falling just short of their all-time April record of 26.3°C, set on April 30, 2004. As of 1 pm today, Halifax was at 27°C, beating their all-time April record. Other major cities in Canada that set all-time warmest March records yesterday included Ottawa (27.4°C), Montreal (25.8°C), Windsor (27.8°C), Hamilton (25.6°C), London (26.4°C), and Fredericton (27.1°C).


Figure 1. The intensity and scope of Summer in March is clearly visible in this data from the Moderate Resolution Imaging Spectroradiometer (MODIS) instrument on the Terra satellite. The map depicts temperatures on March 8 - 15, 2012, compared to the average of the same eight day period of March from 2000-2011. Areas with warmer than average temperatures are shown in red; near-normal temperatures are white; and areas that were cooler than the 2000-2011 base period are blue. These land surface temperatures are distinct from the air temperatures that meteorological stations typically measure, and indicate how hot the surface of the Earth in a particular location would feel to the touch. From a satellite vantage point, the “surface” includes a number of materials that capture and retain heat, such as sand in the desert, the dark roof of a building, or the pavement of a road. As a result, daytime land surface temperature are usually much higher than air temperatures—something that anyone who has walked barefoot across a parking lot on a summer afternoon knows instinctively. Image credit: NASA Earth Observatory.

Summer in March warmth crushes records in Michigan
Yesterday, nearly every major airport in Michigan's Lower Peninsula broke the record they set the previous day for their hottest March temperature, including Detroit (84°), Flint (86°F, just 2° below their all-time April record), Saginaw (87°F, just 2° below their all-time April record), Grand Rapids (87°), Muskegon (82°), Lansing (86°), Alpena (87°), Gaylord (83°, which was 26° above the average high for the date), Pellston (85°), Houghton Lake (85°), and Traverse City (87°, which was which was 45°F above the average high for the date, and was the fifth consecutive day they tied or broke their record for hottest March temperature, and just 3° below their record high temperature of 90° for April.) In Michigan's Upper Peninsula, Sault Ste. Marie's 83° (26° above the average high for the date) crushed the previous March record by 8°, and was only 2° shy of the warmest temperature ever measured in April. Cities in states neighboring Michigan that broke all-time March records for warmth yesterday included:

Indiana:
Fort Wayne (87°) and South Bend (86°)

Ohio:
Columbus (85°), Toledo (85°), Cleveland (83°), and Mansfield (82°)

Wisconsin:
Milwaukee (84°), Madison (83°), and Green Bay (82°). The NWS office in Madison notes that in July of 2009, Madison only had seven days of 80 degree temperatures, and the highest temperature for the whole month was 82. This March, Madison has had five days of 80 degree temperatures, with a high temperature for the month of 83. Prior to this year, there had been only five March 80°F+ days in Madison's history, going back to 1869.

Record March warmth continues in the Northeast U.S.
For the second consecutive day, temperatures across much of Vermont, New Hampshire, and Maine yesterday were the warmest on record for so early in the year. Hottest March temperatures on record occurred at Bangor, Maine (83°F), Houlton, Maine (79°F), Caribou, Maine (75°), Mount Washington, New Hampshire (54°F), and Buffalo, NY (82°).


Figure 2. The jet stream pattern features a large, southwards dipping bulge over the Western U.S., creating a trough of low pressure with cold and snow, and a large, northwards looping bulge over the Central U.S., creating a record-strength ridge of high pressure. The Western U.S. trough has cut off into a "cut-off low" that is slowly drifting eastwards.

Remarkable late-season snow storm on West Coast
The convoluted jet stream pattern that brought Summer in March conditions to the Eastern U.S. and Canada is also bringing record snows to Oregon. Eugene, Oregon picked up 7.5 inches of snow yesterday, the largest snowstorm this late in the year on record. The previous record was a 7.6" snow storm on March 5 - 7, 1951. Snow amounts as high as 32" have been recorded in the Oregon Cascades over the past few days. A loop in the jet stream has created a large upper-level ridge of high pressure that is stuck in place over the Eastern U.S., and large upper-level trough of low pressure over the Western U.S. Since the jet stream acts as the boundary between cold air to the north and warm air to the south, and the large loop in the jet places its axis far to the north of the eastern U.S., summer-like warmth has developed over the eastern half of the U.S. Conversely, colder than average temperatures have developed over the western third of the U.S. behind the southwards-dipping loop of the jet stream. This jet stream pattern was too extreme to be stable, and the big loop over the Western U.S. has broken off to form a giant eddy. The resulting area of low pressure is known as a "cut-off low", because it is cut off from the jet stream. The cut-off low is drifting slowly eastwards, and will bring an end to "Summer in March" over the Eastern half of the U.S. by Friday.

Jeff Masters

Heat Winter Weather

Updated: 2:05 PM GMT en Marzo 23, 2012

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Summer in March: more all-time March temperature records in U.S., Canada

By: JeffMasters, 2:53 PM GMT en Marzo 21, 2012

Summer in March continued for the eighth day yesterday, toppling dozens of records for hottest March day in both the U.S. and Canada. Nearly every major airport in Michigan's Lower Peninsula tied or set records for their hottest March temperature, including Detroit (82°), Flint (84°F), Saginaw (83°F), Grand Rapids (83°), Muskegon (82°), Lansing (83°), Alpena (84°), Gaylord (80°), Pellston (84°), Traverse City (86°), and Houghton Lake (81°). Most of these records will be broken again today or tomorrow. Detroit's current string of six days over 70° is unprecedented so early in the year. One has to go back over 125 years to find an early-season warm spell that compares, and even that streak occurred in April, a full month later (April 16 - 24, 1886.)

Pellston, Michigan in the Northern Lower Peninsula is called "Michigan's Icebox", since it frequently records the coldest temperatures in the state, and in the entire nation. But the past four days, Pellston has topped out at 80° - 84°F, the first 80°F March days in their history. Yesterday's 84° reading broke the previous record for the date (55° in 1976 and 1948) by an unbelievable 29°, and was 44°F above average. Nearby Traverse City hit 86°F yesterday, which was 45°F above the average high for the date, and was the fourth consecutive day with a hottest March temperature on record.


Figure 1. Summer-like temperatures this March in the Midwest have heated up Lake Michigan to record warm levels for this time of year. The average temperature of the lake is characteristic of what occurs in June. Image credit: NOAA. Thanks to wunderground member Neapolitan for posting this image in my blog comments.

Hot times in Lake Michigan
The NWS in Chicago reported yesterday that the Windy City's high of 85°F that day boosted the average temperature for the month to levels that would make March the 7th warmest April in the city's 140-year record. The unprecedented March warmth in the states surrounding Lake Michigan have heated the lake to temperatures never seen before this early in the year. Water temperatures at the South Lake Michigan buoy were 46 - 47°F yesterday (8°C), which is about 10°F above average for this time of year, and typical of early June temperatures.

Record March warmth spreads into New England
Temperatures across much of Vermont, New Hampshire, and Maine yesterday were the warmest on record for so early in the year. Burlington, Vermont's 80°F was 39°F above the average high for the date, and the earliest 80° reading in recorded history. Concord, New Hampshire (81°) and Bangor, Maine (78°), also had their warmest temperatures for so early in the year. The 73°F recorded in Caribou, Maine tied for that city's highest March temperature on record, and broke the record for the date by a remarkable 23°F.

Record warmth continues in Canada
Numerous all-time warmest March temperatures were recorded in Ontario, Canada yesterday, including Windsor at 27°C (previous record, 26.6°C), Sarnia (26°C, previous record 25.6°C), and London (25°C, previous record 24.8°C). High temperatures for Wednesday and Thursday across Ontario, Quebec, New Brunswick, and Nova Scotia are likely to break records for hottest March day for most of the major cities in these provinces, including Toronto, Ottawa, Montreal, St. Johns, and Halifax.


Figure 2. The jet stream pattern features a large, southwards dipping bulge over the Western U.S., creating a trough of low pressure with cold and snow, and a large, northwards looping bulge over the Central U.S., creating a record-strength ridge of high pressure. The Western U.S. trough has cut off into a "cut-off low" that will slowly drift eastwards during the remainder of the week.

Summer in March ends by Friday
The unprecedented Summer in March conditions are due to a loop in the jet stream that has created a large upper-level ridge of high pressure that is stuck in place over the Eastern U.S. Since the jet stream acts as the boundary between cold air to the north and warm air to the south, and the large loop in the jet places its axis far to the north of the eastern U.S., summer-like warmth has developed over the eastern half of the U.S. Conversely, colder than average temperatures have developed over the western third of the U.S. behind the southwards-dipping loop of the jet stream. This jet stream pattern is too extreme to be stable, and the big loop over the Western U.S. has broken off to form a giant eddy. The resulting area of low pressure is known as a "cut-off low", because it is cut off from the jet stream. The cut-off low will drift slowly eastwards during the week, gradually bringing an end to "Summer in March" over the Eastern half of the U.S. by Friday.

How rare is this Summer in March heat event?
One measure of how record-breaking this "Summer in March" heat wave has been is the impact it had on NOAA's National Climatic Data Center web site. The extremes section of the their web site has been down since last Friday, since their software has been unable to handle both the huge number of records being set and the huge demand from people wanting to see these records. The web site came back on-line this morning with software re-engineered to handle the load, but only with data through Sunday.

We can also quantify how rare a meteorological event is by looking at statistics of past years. By averaging together at least 30 years of data to take a representative snapshot of the climate, we can generate a mean and a standard deviation of the data. The standard deviation gives a measure of how much the data fluctuates around the mean.

In comparing deviations from normal across wide regions, it helps to normalize the deviations. A temperature deviation of 3 degrees C may be not that unusual in one region, but may be very significant in another. The solution is to use climatological anomalies (which we often refer to by the Greek letter, sigma.) Calculating the climatological anomaly is a two step process. First, we calculate the difference between a quantity (i.e., temperature) and it's 30-year average value. Then we normalize the difference by dividing it with the 30-year standard deviation. From statistical theory, we know how unusual climatological anomalies are by value:

Odds of a deviation > 1 climatological anomaly=31.7%
Odds of a deviation > 2 climatological anomalies=4.5%
Odds of a deviation > 3 climatological anomalies=0.27%
Odds of a deviation > 4 climatological anomalies=6.34/1000%
Odds of a deviation > 5 climatological anomalies=5.7/100000%
Odds of a deviation > 6 climatological anomalies=1.9/1000000%

So, if we have a 30-year history of high temperatures for a particular date, we'd expect 20 of those years to be 1-sigma years, when the temperature is plus or minus 34% of average (ten colder years, and ten warmer years.) Rare 2-sigma events occur 4.5% of the time, so we should have about 16 of these per year. Even rarer 3-sigma events occur just 0.27% of the time, or just one day per year, on average. Truly extreme 4-sigma events should only occur once every 43 years. Much of Michigan, Wisconsin, Illinois, Minnesota, Northeast Iowa, and the eastern Dakota have experienced multiple 4-sigma days over the past week.

Wunderground is computing 30-year means of the weather for each day of the year using data from the Climate Forecast System Reanalysis (CFSR) (NOMADS data repository). Here is a description how a reanalysis works. CFSR is notable because it is the first reanalysis to use a coupled atmosphere-ocean model. As a result, CFSR has physically consistent estimates of the conditions of the atmosphere, ocean, and land. CFSR has data from 1979 (When polar-orbiting satellites became able to estimate vertical profiles of temperature) to 2010. We can take the mean and standard deviation for each calendar day using this history, and compare it to the current forecast from the GFS model. The result is an image showing how far from average the temperatures are. Yesterday, the analysis showed that Michigan experienced temperatures that were 4 - 5 climatological anomalies warmer than average (4-sigma to 5-sigma), the type of extreme that occurs between once every 43 years and once every 4779 years. Of course, using 30 years of data to estimate extreme events with a return period of centuries is a sketchy proposition. However, keep in mind that had we used a century-long climatology instead of using the past 30 years, yesterday's warmth would have been classified as much more extreme, since the climate has warmed considerably in the past 30 years. It is highly unlikely the warmth of the current "Summer in March" heat wave could have occurred unless the climate was warming.


Figure 3. Climatological anomalies for March 20, 2012. Michigan experienced temperatures that were 4 - 5 climatological anomalies warmer than average (4-sigma to 5-sigma), the type of extreme that occurs between once every 43 years and once every 4779 years. Wunderground plans to make these plots available in real time on our web site later this year.

Heavy rains create flash flood concerns in Texas, Louisiana, and Oklahoma
Widespread rainfall amounts of 3 to 5 inches have fallen over the past two days in Eastern Texas, Eastern Oklahoma, Western Arkansas, and Louisiana over the past two days, creating a serious flash flood hazard. So far, no major river flooding has been reported, and it appears the damage from this flood event will be limited. A few rainfall amounts from the event, from 7 pm CDT Sunday - 3 am CDT Wednesday, taken from the latest NWS Storm Summary:

...TEXAS...
ORANGE 9.68
WACO 6.17
FORT HOOD AAF/KILLEEN 5.43
DALLAS LOVE FIELD 4.49
NWS FORT WORTH 4.13

...OKLAHOMA...
LANGLEY 7.16
NORMAN 5.55
TULSA 4.52
MCALESTER 4.02
OKLAHOMA CITY 3.18

...LOUISIANA...
FORT POLK 6.14
SHREVEPORT 4.06
LAKE CHARLES 2.11

...ARKANSAS...
FORT SMITH 3.49
BENTONVILLE 3.09
LITTLE ROCK 2.22
FAYETTEVILLE 2.08


Jeff Masters

Heat

Updated: 5:54 PM GMT en Marzo 21, 2012

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Torrential rains in Oklahoma; Summer in March continues for Midwest

By: JeffMasters, 2:07 PM GMT en Marzo 20, 2012

A significant flood event is underway in Eastern Oklahoma, where widespread rainfall amounts of 3 to 5 inches have fallen since yesterday. Up to four more inches of rain is likely today, and the National Weather Service in Tulsa is warning of the potential for "widespread and potentially catastrophic areal flooding and river flooding" should some of the higher rainfall amounts being forecast materialize. Numerous main-stem rivers across eastern Oklahoma and northwest Arkansas are now approaching flood stage, and will likely experience moderate to major flooding into Wednesday. Rainfall has also been heavy over Eastern Texas, with widespread amounts of 2 - 4 inches. These heavy rains are causing some street flooding, but in general, will be a benefit, as moderate to severe drought conditions still cover most of the region.


Figure 1. Radar-estimated rainfall for Eastern Oklahoma since March 19, 2012, as estimated by the Tulsa, Oklahoma radar.

The storm system responsible is a massive, slow-moving trough of low pressure over the Western U.S. that is colliding with the warmest and moistest air mass ever recorded in March in the Central and Eastern U.S. According to the NWS in Minneapolis, Minnesota, moisture flowing northwards into Minnesota along the cold front early this week had the highest levels of moisture ever recorded so early in the year. At the boundary between the Western U.S. trough of low pressure and Central U.S. ridge of high pressure, a cold front is lifting huge quantities of moisture-laden air aloft, forcing torrential rains to fall. The cold front is also expected to trigger a Slight Risk of severe weather over East Texas, Western Louisiana, and Southern Arkansas today, says NOAA's Storm Prediction Center. Severe thunderstorm watches are already posted for much of East Texas, as seen on our Severe Weather Map. Three tornadoes were reported yesterday in Texas, and eleven touched down the previous day in Oklahoma, Nebraska, and South Dakota. The tornado that hit North Platte, Nebraska two days ago was rated a strong EF-3, and injured four people.


Figure 2. Predicted rainfall amounts for the 2-day period Tuesday morning through Thursday morning show an area of 3+ inches (orange colors) is expected over Eastern Oklahoma, Arkansas, Louisiana, and Southwest Missouri. Image credit: NOAA HPC.

Summer in March continues for the Midwest
The ongoing March heat wave in the Midwest will continue to set all-time heat records through Thursday, gradually shifting its peak intensity eastwards during the week. A few highlights from yesterday's records:

Pellston, Michigan in the Northern Lower Peninsula is called "Michigan's Icebox", since it frequently records the coldest temperatures in the state, and in the entire nation. But the past three days, Pellston has topped out at 80° - 82°F, the first 80°F March days in their history. Yesterday's 82° reading broke the previous record for the date (56° in 1976) by an amazing 26°, and was 44°F above average. Nearby Traverse City hit 83°F yesterday, the third consecutive day the city has experienced its hottest March temperature on record.

International Falls, Minnesota hit 78°F yesterday, 42° above average, and the 2nd hottest March temperature on record in the Nation's Icebox. The record of 79°F was set the previous day. Remarkably, the low temperature for International Falls bottomed out at 60°F yesterday, tying the previous record high for the date. I've never seen a station with a century-long data record have its low temperature for the date match the previous record high for the date. Yesterday was the seventh consecutive day that International Falls broke or tied a daily record. That is spectacularly hard to do for a station with a century-long weather record. The longest string of consecutive records being broken I'm aware of is nine days in a row, set June 2 - 10, 1911 in Tulsa, Oklahoma (with weather records going back to 1905.) International Falls has a good chance of surpassing nine consecutive records this week.

Record heat in Canada
Record-breaking heat has also penetrated into the Prairie provinces of Canada over the past week. Winnipeg, Manitoba has broken its record high for the past five days in a row, and hit 24°C (75.2°F) yesterday, its hottest March temperature on record. Forecast high temperatures for Wednesday and Thursday across Ontario are near 26°C, which will threaten the records for hottest March day in history for Windsor, London, Hamilton, and Toronto.


Figure 3. The jet stream pattern features a large, southwards dipping bulge over the Western U.S., creating a trough of low pressure with cold and snow, and a large, northwards looping bulge over the Central U.S., creating a record-strength ridge of high pressure.

Why the record early-season warmth?
The unusual warmth is due to a loop in the jet stream that has created a large upper-level ridge of high pressure that is stuck in place over the Eastern U.S.--a phenomenon known as a "blocking pattern." Since the jet stream acts as the boundary between cold air to the north and warm air to the south, and the large loop in the jet places its axis far to the north of the eastern U.S., summer-like warmth has developed over the eastern half of the U.S. Conversely, colder than average temperatures have developed over the western third of the U.S. behind the southwards-dipping loop of the jet stream. This jet stream pattern is too extreme to be stable, and the big loop over the Western U.S. will break off and form a giant eddy on Wednesday. The resulting area of low pressure will be known as a "cut-off low", because it will be cut off from the jet stream. The cut-off low will drift slowly eastwards during the week, gradually bringing an end to "Summer in March" over the Eastern half of the U.S.

Jeff Masters

Heat Flood

Updated: 2:41 PM GMT en Marzo 20, 2012

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Tornadoes, extreme flooding, unprecedented heat expected in U.S. today

By: JeffMasters, 3:04 PM GMT en Marzo 19, 2012

Widespread and potentially catastrophic areal flooding and river flooding is expected this afternoon through Wednesday morning in Eastern Oklahoma, Western Arkansas, Western Louisiana, and Southwest Missouri, warns the National Weather Service in Tulsa, Oklahoma, in their latest flood watch for the region. The storm system responsible is a massive, slow-moving trough of low pressure over the Western U.S. that dumped heavy snows that closed several interstate highways in Arizona over the weekend. This storm system will collide with the warmest and moistest air mass ever recorded in March in the Central and Eastern U.S. According to the NWS in Minneapolis, Minnesota, moisture flowing northwards into Minnesota along the cold front yesterday had the highest levels of moisture ever recorded so early in the year, and moisture levels are expected to remain at record levels today. At the boundary between the Western U.S. trough of low pressure and Central U.S. ridge of high pressure, a cold front will lift huge quantities of moisture-laden air aloft, forcing record rains to fall. A wide region of 4 - 8 inches of rain is expected in the flood watch area, and isolated amounts as high as 15 inches could fall by Wednesday, as numerous rounds of thunderstorms repeatedly track over the same area. The cold front is also expected to trigger a Moderate Risk of severe weather over much of Texas today, including the Dallas-Fort Worth area, says NOAA's Storm Prediction Center. Damaging winds, large hail, flash flooding, and few strong tornadoes are expected to affect the area late this afternoon. Severe thunderstorm watches are already posted for much of West Texas, as seen on our Severe Weather Map. Eleven tornadoes were reported yesterday in Oklahoma, Nebraska, and South Dakota.


Figure 1. Predicted rainfall amounts for the 3-day period Monday morning through Thursday morning show an area of 7+ inches (yellow colors) is expected over Eastern Oklahoma, Western Arkansas, Western Louisiana, and Southwest Missouri. Image credit: NOAA HPC.


Figure 2. NOAA's Storm Prediction Center has highlighted a Moderate Risk area for severe weather over much of Texas today, including the Dallas-Fort Worth area.

Summer in March for the Midwest
The ongoing March heat wave in the Midwest is one of the most extreme heat events in U.S. history. With so many records being shattered, it is difficult to cover in detail just how widespread, long-lasting, and extreme the event is, and I offer just a few highlights:

Winner, South Dakota hit 94°F yesterday, the earliest 90°+ reading ever recorded in the Northern Plains, according to wunderground's weather historian, Christopher C. Burt. The 94°F reading was just 2°F short of the all-time state record for South Dakota in March, which was 96°F in Tyndall in 1943. However, subsequent analysis by NOAA questioned this 94°F reading, and it is now believed that 87°F is the appropriate high for Winner.

International Falls, Minnesota hit 79°F yesterday, the hottest March temperature on record in the Nation's Icebox. At midnight this morning, the temperature was 66°F there, breaking the record high for March 19 (set in 1910) by 6°F. The low temperature for International Falls bottomed out near 60°F this morning, so low for today is (unofficially) the same as the previous record high for the date. This is the seventh consecutive day that International Falls has broken or tied a daily record. That is spectacularly hard to do for a station with a century-long weather record. The longest string of consecutive records being broken I'm aware of is nine days in a row, set June 2 - 10, 1911 in Tulsa, Oklahoma (with weather records going back to 1905.) International Falls has a good chance of surpassing nine consecutive records this week.

Houghton, Michigan, near the frigid shores of Lake Superior, hit 76°F both Saturday and Sunday. It was the hottest March temperature on record, and an astonishing 44°F above the average high for the date (Saturday) of 32°. Huron, South Dakota also recorded a high temperature (88°F) that was 44° above the average high for the date, on Sunday. Most of the cities in Northern Michigan set all-time March high temperature records over the weekend.

Chicago, Illinois now has a string of five consecutive days of 80°+ temperatures, and the hottest temperature on record for so early in the year (82°F on Friday, and tied again on Saturday). The average high temperature in August is 82°F in Chicago, so this week is basically summer weather. Prior to this year, there had only been 10 days in March with highs in the 80s in Chicago, going back to 1871. The last time Chicago saw an 80 degree temperature during the month of March (prior to this year) was over 22 years ago back on March 12, 1990 when the high temperature hit 81. This morning's Public Information Statement from the National Weather Service in Chicago had this to say about this unprecedented March heat:

Chicago and Rockford have now both broken high temperature records 5 days in a row. There is even the potential they could tie or break record highs for up to an unbelievable 8 days in a row depending on how warm temperatures get Monday through Wednesday. It is extraordinarily rare for climate locations with 100+ year long periods of records to break records day after day after day.


Figure 3. March's month-to-date average temperature compared to the other top 5 warmest months of March in Chicago. The dotted blue lines are month-to-date average temperatures based on the current predicted temperatures. The hashed black line is the average month to date temperature for March. These graphs really illustrate just how far above the previous warmest top 5 Marches this month really has been and assuming no major pattern change the last week of the month gives some indication of just how far above the record March 2012 could end up being. Image credit: NWS Chicago.

Record heat in Canada
Record-breaking heat has also penetrated into the Prairie provinces of Canada over the past week. Winnipeg, Manitoba broke its record high for the past four days in a row, and hit 21°C yesterday, its hottest temperature on record so early in the year. With today's forecast by Environment Canada and wunderground both calling for highs near 25°C (77°F), Winnipeg is likely to record its highest March temperature on record. Previous record: 23.3°C on March 27, 1946. The earliest date for a 25°C+ temperature in Winnipeg is April 9, 1977.


Figure 4. The jet stream pattern features a large, southwards dipping bulge over the Western U.S., creating a trough of low pressure with cold and snow, and a large, northwards looping bulge over the Central U.S., creating a record-strength ridge of high pressure.

Why the record early-season warmth?
The unusual warmth is due to a loop in the jet stream that has created a large upper-level ridge of high pressure that is stuck in place over the Eastern U.S.--a phenomenon known as a "blocking pattern." Since the jet stream acts as the boundary between cold air to the north and warm air to the south, and the large loop in the jet places its axis far to the north of the eastern U.S., summer-like warmth has developed over the eastern half of the U.S. Conversely, colder than average temperatures have developed over the western third of the U.S. behind the southwards-dipping loop of the jet stream. There are at least three large-scale patterns working together right now to create an unusually strong ridge over the eastern half of the U.S.:

1) La Niña. The on-going La Niña event in the Eastern Pacific has weakened considerably over the past month, but ocean temperatures there are still cool enough to affect the jet stream pattern, favoring high pressure and warm temperatures over the Eastern U.S., and low pressure and cold temperatures over the Western U.S.

2) The Madden-Julian Oscillation( MJO). The MJO is a 2-month cycle of thunderstorm activity that travels west to east along the Equator. The MJO is currently in phase with La Niña, and is helping create warmer temperatures over the Eastern U.S.

3) The North Atlantic Oscillation (NAO.) The NAO is in its positive phase, which means the difference in pressure between the Icelandic Low and the Azores High is stronger than usual. This tends to increase the jet stream winds and keeps the jet from sagging southwards over the Eastern U.S.

While the blocking pattern responsible for the heat wave is natural, it is very unlikely that the intensity of the heat would have been so great unless we were in a warming climate. Climate scientist Dr. James Hansen has posted an interesting (as yet unpublished) paper discussing how the odds of such extreme heat events have shifted in recent years.

Extreme jet stream patterns like this often lead to tornado outbreaks in the Midwest, at the boundary of where warm, moist air flowing north from the Gulf of Mexico collides with cold, dry air flowing south. Cold dry air aloft, combined with warm, moist air at the surface, makes the atmosphere unstable, since air rising in thunderstorm updrafts will be less dense than the surroundings, allowing the air to accelerate upwards and increase the intensity of the thunderstorm. This will be the case today, when NOAA's Storm Prediction Center has highlighted a Moderate Risk area for severe weather over much of Texas today, including the Dallas-Fort Worth area.

Flood risk low this year for the Northern Plains
For the first time in four years, the Northern Plains are not expecting major to record snow melt flooding, said NOAA's National Weather Service in their annual spring flood outlook issued last week. Residents along the Mississippi, Missouri, Red, and Souris Rivers have endured a punishing series of bad flood years, but this year is unlikely to continue that trend, due to a lack of snow cover. The Northern Plains states of Minnesota, Wisconsin, North Dakota, and South Dakota recorded their 3rd - 8th warmest winter in the 117-year record, and are on pace to crush the record for warmest March in history. Winter snowfall was below average over most of the region, and what snow was on the ground at the beginning of March has mostly melted, thanks to the record-breaking March heat this week. The Souris and Red River basins contain about one-third the amount of water in the snow as last year, ranking this season in the lower half of the last 60 years. Precipitation this water year (since Oct 1, 2011) has been less than 50% of the normal across the Upper Mississippi and Upper Missouri Valleys, and much of the region is under moderate to severe drought, according to the latest Drought Monitor.


Figure 5. What a difference a year makes! Snow cover on March 15 of last year (top) was heavy over Minnesota, Wisconsin, and the Dakotas, and caused massive flooding problems on the Mississippi and Missouri Rivers during spring melt season. In contrast, there is almost no snow pack in the Upper Midwest this year (bottom), significantly reducing the odds of spring flooding on the Missouri and Mississippi Rivers. Image credit: NOAA/NOHRSC.


Figure 6. The U.S. spring flood risk, as predicted by the National Weather Service on March 15, 2012.

Jeff Masters

Heat Severe Weather

Updated: 7:37 PM GMT en Marzo 28, 2012

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Nation's Icebox basks in 77°F warmth

By: JeffMasters, 1:08 PM GMT en Marzo 18, 2012

Each year, when the list of coldest U.S. cities is compiled, International Falls, Minnesota regularly winds up at the top of the list, earning its title as "Icebox of the Nation". The city once hit -55°F (on January 6, 1909), and takes pride in the distinction of being the coldest city in the U.S., having trademarked the term "Icebox of the Nation" in 1948. The city recently defended the trademark against the town of Fraser, Colorado, which sought to usurp the title as the Nation's Icebox. But yesterday, International Falls set a truly phenomenal weather record for warmth. The city's temperature soared to 77°F, which was 42° above the average high temperature for the date. Not only was it the city's hottest March temperature on record by 4°, it was just 4° shy of yesterday's high in Miami, Florida. But what was truly amazing is that the 77°F high in International Falls beat the previous record for the date by 22°! I talked to Christopher C. Burt, wunderground's weather historian, and he couldn't recall seeing a station with a century-plus period of weather records break a daily record by such a wide margin (International Falls' records go back to 1895.) Yesterday's temperatures in International Falls were but one chapter in the on-going story of one of the most extreme meteorological events in U.S. history. Never before has such an extended period of extreme and record-breaking warm temperatures affected such a large portion of the U.S. in March, going back to the beginning of record keeping in the late 1800s. The record-breaking warmth will continue through Thursday, and I'll have much more to say in Monday's post.

Jeff Masters

Heat

Updated: 1:08 PM GMT en Marzo 18, 2012

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Summer in March continues for Midwest; Dexter, MI tornado an EF-3

By: JeffMasters, 1:54 PM GMT en Marzo 17, 2012

For the third consecutive day, Chicago, Illinois hit their warmest temperature on record so early in the year, going back to 1872. The mercury hit 82°F, giving the city its third consecutive day of 80°+ temperatures, smashing the old record by a month. Previously, the earliest Chicago had ever seen three consecutive 80 degree days was back on April 14 - 16, 1976. This morning's Public Information Statement from the National Weather Service in Chicago had this to say:

Chicago and Rockford have both broken high temperature records 3 days in a row and will likely break record highs for 5 days in a row. There is even the potential they could tie or break record highs for 6 or 7 days in a row depending on how warm temperatures get on Monday and Tuesday. It is extraordinarily rare for climate locations with 100+ year long periods of records to break records day after day after day. At the current pace... it is likely that Chicago and Rockford will not only break... but shatter their current record warmest Marches.


Figure 1. "This is the kind of sunset that you can expect to see in July, not in March. 77degrees when I took this," said the caption on this wunderphoto taken yesterday in Windom, Minnesota by wunderphotographer sally.

Minneapolis, Minnesota hit 79°F yesterday, the warmest it's ever been this early in the year, going back to 1872, and 39°F above average. This smashes the old record by a remarkable 6°F. Previous record: 73°F, set just two days previously, and also on March 7, 2000.

Bismark, North Dakota hit 81°F yesterday, which was a remarkable 41°F above normal. Not only does this tie Bismarck's warmest all-time monthly March temp on record (three other 81°F readings later in the month, with March 22,1910 being next earliest), it beats the next warmest early season record by a full 6°! The previous record was 75°F on March 12, 2007. Temperatures also soared into the 70's well into Canada's prairies on Friday, setting all-time warm temperature records for so early in the year across much of southern Canada.

International Falls, Minnesota hit 71°F yesterday, which was 36°F above normal, and their earliest 70°F reading by two weeks. Previously, the earliest 70°F reading came on March 30, 1967. Back on March 17, 1897, the temperature in International Falls hit -33°F!

Dexter, Michigan tornado rated an EF-3
NWS survey teams have confirmed that an EF-3 tornado with winds of 135 - 140 mph hit Dexter, Michigan on Thursday. It was the earliest EF-3 or stronger tornado in Michigan history, going back to 1950. The tornado skipped along a 7.2-mile path and had a width of up to 800 yards. It damaged or destroyed 128 buildings, but fortunately did not cause any deaths or injuries. The previous earliest appearance of an F-3 tornado in Michigan was on March 20, 1976. At least two other tornadoes touched down in Michigan Thursday, making it the second largest tornado outbreak in state history so early in the year. The record outbreak for so early in the year was the eight tornadoes that touched down on March 12, 1976.


Figure 2. Radar reflectivity image of the March 15, 2012 Dexter, Michigan tornado.

I'll be back Monday with a new post.

Jeff Masters

Heat Tornado

Updated: 12:25 AM GMT en Marzo 18, 2012

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Rare March tornado rips Michigan; record March heat wave sets more records

By: JeffMasters, 2:43 PM GMT en Marzo 16, 2012

As I stepped out of my front door into the pre-dawn darkness from my home near Ann Arbor, Michigan yesterday morning, I braced myself for the cold shock of a mid-March morning. It didn't come. A warm, murky atmosphere, with temperatures in the upper fifties--30 degrees above normal--greeted me instead. Continuous flashes of heat lightning lit up the horizon, as the atmosphere crackled with the energy of distant thunderstorms. Beware the Ides of March, the air seemed to be saying. I looked up at the hazy stars above me, flashing in and out of sight as lightning lit up the sky, and thought, this is not the atmosphere I grew up with.


Video 1. Video taped at Hudson Mills Metro Park in Dexter about 5:30PM on March 15, 2012, by Matthew Altruda from Tree Town Sound, http://www.treetownsound.com. Caution: foul language.

That afternoon, as the Detroit temperature soared to 77°F, the second warmest on record so early in the year, going back to 1871, I watched as late afternoon thunderstorms built with remarkable speed. Though NOAA's Storm Prediction Center had placed Southeast Michigan in their "Slight Risk" area for severe weather, I wasn't too concerned about tornadoes. We don't get many tornadoes in Michigan this early in the year, and certainly not strong ones. Prior to yesterday, there were only sixteen tornadoes on record in Michigan that occurred before March 16, going back to 1950. Though the air was remarkably unstable for this time of year, the upper level winds were not strong enough to generate much shearing action on the air, meaning that tornadoes would have a tough time getting spinning. But the atmosphere had other ideas. In a remarkably short half-hour period, a severe thunderstorm sprang up west of Ann Arbor, began spinning, and dropped a strong tornado down on the unfortunate town of Dexter, Michigan. The tornado skipped along a ten-mile path, damaging or destroying 128 buildings, but fortunately not causing any deaths or injuries. While most of the damage was light to moderate, thirteen homes were demolished, and preliminary damage estimates from the National Weather Service put the twister at the boundary between EF-2 and EF-3 strength, with winds of 135 mph. If confirmed as an EF-3, this would be the earliest EF-3 or stronger tornado in Michigan history, going back to 1950, according to data from The Tornado History Project. The previous earliest appearance of an F-3 tornado in Michigan was on March 20, 1976. At least two other tornadoes touched down in Michigan yesterday, making it the second largest tornado outbreak in state history so early in the year. The record outbreak for so early in the year was the eight tornadoes that touched down on March 12, 1976.



Figure 1. Radar reflectivity image (top) and Doppler velocity image (bottom) of the March 15, 2012 Dexter, Michigan tornado.


Video 2. This video report by AnnArbor.com's Nathan Bomey shows tornado damage in the Dexter, Michigan, about 90 minutes after the tornado came through on Thursday, March 15, 2012.

I talked to a friend in Dexter who relayed the story of her friend who was driving through town, saw the tornado, and pulled over into the Dexter car wash to take shelter. Some strangers living next door to the car wash yelled at him to come shelter in their basement, since the car wash didn't have a basement. He joined them, and was glad he did, because his car and the car wash were heavily damaged by a tree that was flung into it (see damage to the car wash in the video above.)

Hail, Hail, to Michigan
The Dexter storms also brought golfball to baseball-sized hail and a deluge of 4 - 5 inches of rain that caused street flooding in Ann Arbor. My Ph.D. advisor and co-founder of Weather Underground, Dr. Perry Samson, related this story to me: "I was traveling home by bus to go chase, but the bus came to a stand still at Michigan Stadium as cars were sunk up to their windows in water on Main Street. I told the driver I had to chase this storm, and came up with a story about what I do. He gunned the bus and drove through the flood to get me home. So I didn't actually commandeer a bus to chase the tornado, but it was darn close!"

Record Midwest March heat wave topples more records
For the second consecutive day, large portions of Illinois, Wisconsin, and Iowa, including the cities of Chicago, Madison, and Dubuque, recorded their all-time warmest temperatures for so early in the year. Perhaps the most extraordinary record occurred in Madison, Wisconsin, which hit 82°F--a temperature 39°F above average. It was the hottest temperature ever recorded in March, and three degrees warmer than any day so early in the year, going back to 1869. Not as many all-time hottest temperature records for so early in the year were set in Michigan and other surrounding states, due to plentiful moisture that generated afternoon cloud cover. The records will continue to fall across the Midwest for another week, as the ridge of high pressure responsible stays locked in place.

Major airports that set all-time heat records yesterday
For the second consecutive day, Chicago, Illinois hit 81°F; the warmest it's ever been this early in the year, going back to 1872, and 35°F above average. This ties the record set on March 12, 1990.

For the second consecutive day, Springfield, Illinois hit 83°F, the warmest it's ever been this early in the year, going back to 1879, and 32°F above average. This ties the record of 83°F on March 13, 1918.

Rockford, Illinois hit 82°F, the warmest it's ever been this early in the year, going back to 1893, and 36°F above average. Previous record: 79°F set the previous day.

Moline, Illinois hit 81°F, the warmest it's ever been this early in the year, going back to 1874, and 33°F above average. Previous record: 80°F on March 12, 1990.

Dubuque, Iowa hit 78°F, the warmest it's ever been this early in the year, going back to 1874, and 34°F above average. Previous record: 75°F set the previous day, and also on March 12, 1990.

Waterloo, Iowa hit 79°F, the warmest it's ever been this early in the year, going back to 1895, and 34°F above average. This ties the record set on March 7, 2000.

Madison, Wisconsin hit 82°F, the warmest it's ever been this early in the year, going back to 1869, and 39°F above average. This is also the warmest temperature ever recorded in March (tied with March 29th, 1986 and March 31, 1981), as is also (by two weeks) the earliest 80° reading ever measured there. The previous record for a temperature so hot this early in the year was 79°F set the previous day, on March 14, 2012.

Data for the previous records was taken from NOAA's National Climatic Data Center (NCDC).

I'll have a new post on Saturday.

Jeff Masters

Tornado Heat

Updated: 7:05 PM GMT en Marzo 16, 2012

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Unprecedented early-year heat smashes all-time records in Midwest

By: JeffMasters, 2:04 PM GMT en Marzo 15, 2012

The first day of spring doesn't arrive until Tuesday, but Mother Nature has fast-forwarded past spring and gone straight to summer over the Midwest. Yesterday, large portions of Michigan, Illinois, Wisconsin, Minnesota, and Indiana recorded their all-time warmest temperatures for so early in the year, including the cities of Chicago, Minneapolis, Indianapolis, Milwaukee, and Lansing. Temperature records for these cities go back as far as 1863. Perhaps the most extraordinary record was set in Traverse City, Michigan, which hit 81°F--a temperature 42°F above the average high for the date, and four degrees warmer than any previous day so early in the year. Records go back to 1897 in the city.


Figure 1. Spring has arrived early in Sherrard, Illinois, and much of the Midwest, thanks to a record-breaking March heat wave. Image credit: wunderphotographer JourneysEnd.

Major airports that set all-time heat records yesterday

Chicago, Illinois hit 81°F; the warmest it's ever been this early in the year, going back to 1872, and 35°F above average. This ties the record set on March 12, 1990.

Springfield, Illinois hit 83°F, the warmest it's ever been this early in the year, going back to 1879, and 32°F above average. This ties the record of 83°F on March 13, 1918.

Rockford, Illinois hit 79°F, the warmest it's ever been this early in the year, going back to 1893, and 33°F above average. Previous record: 78°F on March 7, 2000.

Peoria, Illinois hit 81°F, the warmest it's ever been this early in the year, going back to 1883, and 31°F above average. Previous record: 80°F on March 12, 1990.

Minneapolis, Minnesota hit 73°F, the warmest it's ever been this early in the year, going back to 1872, and 33°F above average. This ties the 73°F reading of March 7, 2000.

Grand Rapids, Michigan hit 80°F, the warmest it's ever been this early in the year, going back to 1892, and 37 degrees above average. Previous record: 78°F on March 8, 2000.

Muskegon, Michigan hit 77°F, the warmest it's ever been this early in the year, going back to 1896, and 35°F above average. Previous record: 73°F on March 8, 2000.

Traverse City, Michigan hit 81°F, the warmest it's ever been this early in the year, going back to 1897, and 42°F above average. Previous record: 77°F on March 7, 2000.

Lansing, Michigan hit 79°F, the warmest it's ever been this early in the year, going back to 1863, and 36°F above average. This ties the record of 79°F on March 8, 2000.

Indianapolis, Indiana hit 81°F, the warmest it's ever been this early in the year, going back to 1871, and 30°F above average. Previous record: 80°F on March 8, 1974 and March 13, 2007.

South Bend, Indiana hit 81°F, the warmest it's ever been this early in the year, going back to 1893, and 35°F above average. Previous record: 80°F on March 8, 2000.

Evansville, Indiana hit 82°F, the warmest it's ever been this early in the year, going back to 1871, and 25°F above average. This ties the record of 82°F set on March 10, 1990.

Milwaukee, Wisconsin hit 78°F, the warmest it's ever been this early in the year, going back to 1869, and 36°F above average. Previous record: 77°F on March 7 and 8, 2000.

Madison, Wisconsin hit 78°F, the warmest it's ever been this early in the year, going back to 1869, and was 36°F above average. Previous record: 77°F on March 8, 2000.

Green Bay, Wisconsin hit 75°F, the warmest it's ever been this early in the year, going back to 1886, and 37°F above average. Previous record: 74°F on March 8, 2000.

Dubuque, Iowa hit 75°F, the warmest it's ever been this early in the year, going back to 1874, and 37°F above average. This ties the 75°F reading of March 12, 1990.

Data for the previous records was taken from NOAA's National Climatic Data Center (NCDC).

Why the record early-season warmth?
The unusual warmth is due to a loop in the jet stream that has created a large upper-level ridge of high pressure that is stuck in place over the Eastern U.S.--a phenomenon known as a "blocking pattern." Since the jet stream acts as the boundary between cold air to the north and warm air to the south, and the large loop in the jet places its axis far to the north of the eastern U.S., summer-like warmth has developed over the eastern half of the U.S. Conversely, colder than average temperatures have developed over the western third of the U.S. behind the southwards-dipping loop of the jet stream. There are at least three large-scale patterns working together right now to create an unusually strong high-pressure ridge over the eastern half of the U.S.:

1) La Niña. The on-going La Niña event in the Eastern Pacific has weakened considerably over the past month, but ocean temperatures there are still cool enough to affect the jet stream pattern, favoring high pressure and warm temperatures over the Eastern U.S., and low pressure and cold temperatures over the Western U.S.

2) The Madden-Julian Oscillation( MJO). The MJO is a 2-month cycle of thunderstorm activity that travels west to east along the Equator. The MJO is currently in phase with La Niña, and is helping create warmer temperatures over the Eastern U.S.

3) The North Atlantic Oscillation (NAO.) The NAO is in its positive phase, which means the difference in pressure between the Icelandic Low and the Azores High is stronger than usual. This tends to increase the jet stream winds and keeps the jet from sagging southwards over the Eastern U.S.

While the blocking pattern responsible for the heat wave is natural, it is improbable that the intensity of the heat would have been so great unless we were in a warming climate. Climate scientist Dr. James Hansen has posted an interesting (as yet unpublished) paper discussing how the odds of such extreme heat events have shifted in recent years. I plan to discuss these concepts in more detail next week.


Figure 2. Predicted high temperatures for Thursday, March 15, 2012 over much of the Midwest are more typical of June than March.

The forecast
The summer-like heat continues today over the Midwest, with the greatest departures from average (30°+) expected over Wisconsin, Iowa, Illinois, Indiana, and Michigan. This area of 30°+ above average temperatures will expand to stretch from South Dakota to New York on Sunday and Monday, then gradually shift eastwards, extending from Wisconsin to Maine by Wednesday. The jet stream loop is predicted to grow more pronounced this weekend, and reach a truly extreme configuration on Monday and Tuesday. On those days, the predicted strength of the upper-level ridge of ridge pressure along the northern tier of states, from Wisconsin to Maine, will be typical of what we see at the height of summer, during July and August. The GFS and ECMWF models are predicting the height at where a pressure of 500 mb is found will range between 5760 - 5800 meters on those days--7% higher than the typical mid-March 500 mb heights of 5460 meters. Record-breaking summer-like temperatures will last until at least Friday, March 23, for much of the Midwest and Northeast U.S.

Extreme jet stream patterns like this often lead to tornado outbreaks in the Midwest, at the boundary of where warm, moist air flowing north from the Gulf of Mexico collides with cold, dry air flowing south. Cold dry air aloft, combined with warm, moist air at the surface, makes the atmosphere unstable, since air rising in thunderstorm updrafts will be less dense than the surroundings, allowing the air to accelerate upwards and increase the intensity of the thunderstorm. This will be the case on Sunday, when NOAA's Storm Prediction Center has highlighted a potential risk area for severe weather from Texas northwards through Nebraska. Fortunately, the winds of the jet stream are expected to blow almost due south to north over the region by Monday, which may limit the amount of cold air aloft that can overrun the warm air at the surface, resulting in a more stable atmosphere and a reduced chance of severe weather compared to Sunday.

Jeff Masters

Heat

Updated: 12:25 AM GMT en Marzo 16, 2012

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Remarkable week-long March heat wave hitting U.S.

By: JeffMasters, 4:02 PM GMT en Marzo 14, 2012

A highly unusual week-long heat wave is building over much of the U.S., and promises to bring the warmest temperatures ever seen so early in year to a large portion of the Midwest. The exceptional heat will also be exceptionally long-lasting: record-breaking temperatures 20 - 30 degrees F above normal are expected today through next Wednesday for much of the Midwest and Northeast U.S. The weather system responsible is a large upper-level ridge of high pressure that is "stuck" in place--a phenomenon known as a "blocking pattern." The jet stream is bending far to the south over the Western U.S., then bending far to the north over the Rockies and into Canada, and lies far to the north of the eastern U.S. Since the jet stream acts as the boundary between cold air to the north and warm air to the south, the current looping pattern is bringing colder than normal temperatures and snow to the mountains of the West, and summer-like warmth to the Eastern U.S. It is common for the jet stream to get stuck in a blocking pattern for a period of a week or more, but not in to this extremity. If the current model forecasts prove correct, a high pressure ridge over the U.S. bringing heat this intense and long-lasting in March will be unprecedented in the historical record, going back to 1872.


Figure 1. Is this March or June? Predicted high temperatures for Wednesday, March 14, 2012 over much of the Midwest are more typical of June than March.

Here are the hottest all-time recorded temperatures measured prior to March 20 for some selected U.S. cities. All of these records will be seriously threatened during the coming week:

Madison, WI: 77°F on March 7, 2000
Milwaukee, WI: 77°F on March 7 - 8, 2000
Minneapolis, MN: 73°F on March 7, 2000
Des Moines, IA: 82°F on March 11, 1972
Chicago, IL: 81°F on March 12, 1990
Detroit, MI: 80°F on March 8, 2000
Lansing, MI: 79°F on March 8, 2000
Muskegon, MI: 73°F on March 8, 2000
Grand Rapids, MI: 78°F on March 8, 2000
Flint, MI: 80°F on March 8, 2000

As you can see, the expected warm temperatures during the coming week will rival those recorded on March 8, 2000, when most of the Upper Midwest set all-time records for the warmest temperature ever measured so early in the year. That warm surge was caused by a ridge of high pressure that was not as strong as the one expected to build in during the coming week, and the March 8, 2000 ridge did not stick around long enough to generate more than two days of record-breaking high temperatures. A powerful low pressure system moved through Northern Wisconsin on March 8, 2000, dragging a cold front through the state that triggered a thunderstorm that spawned the earliest tornado ever recorded in Milwaukee County.


Figure 2. New daily high temperature records were set at 208 locations yesterday, according to our new Extremes web page, with data from NOAA's National Climatic Data Center.

Hot days in Minneapolis
In Minneapolis, Minnesota yesterday, the high temperature reached 67°F, which is the 7th warmest temperature measured so early in the year, and 27°F above the normal high of 40°F for the date. Since weather records in the city go back to 1872, we can expect that Minneapolis will experience a temperature of 67°F or higher this early in the year once every 20 years, on average. What's really remarkable is that the forecast for Minneapolis calls for a high temperature of 70 - 75° every day for the next seven days. Since 1872, there have only been nine days that the temperature has gotten to 70°F prior to March 20, with 73°F on March 7, 2000 being the hottest day. So, over the course of the next week, we are likely to break the all-time high for so early in the year, and add nearly double the number of 70°F-plus days. The situation is similar for much of Wisconsin, Michigan, Illinois, and surrounding states. With temperatures already averaging at least 5°F over much of the Midwest this month, it's very likely that this month will be the warmest March on record for at least seven states.

Unusual snows on the Oregon coast
As is often the case, record heat in one part of the country means that another part is experiencing unusual cold, due to a kink in the jet stream. On Monday, 6.0" of snow fell at Newport, OR, and 8.5" at Tillamook (about halfway up the coast between Newport and Astoria). According to statistics at the Western Regional Climate Center, the Newport snowfall was their greatest March snowfall on record (previous was 2.0" in March 1906) and the their 3rd greatest snowfall of any month since records began in 1893. The latest-greater snowfall at Newport was 11.0" on Dec. 3-4, 1972. This tied with another 11.0" snow in January 1943 as their greatest snowfalls on record. For Tillamook it was the biggest snow since 9.0" in January 1971 (but well short of their all-time snowfall of 19.0" in March 1951).

Jeff Masters

Heat

Updated: 6:56 PM GMT en Marzo 14, 2012

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March 2 - 3 tornado outbreak: 10th largest in recorded history?

By: JeffMasters, 3:06 PM GMT en Marzo 12, 2012

The deadly early-season tornado outbreak of March 2 - 3 that hit Indiana, Kentucky, and surrounding states, killing 41 people, may have been the 10th largest two-day tornado outbreak since record keeping began in 1950. NOAA's Storm Prediction Center now lists 132 preliminary tornado reports for March 2, and 11 for March 3. It typically takes several months to finish damage surveys and verify all the tornadoes that really occur in a big tornado outbreak. Sixty-one tornadoes have been confirmed so far, according to Wikipedia's tally of the outbreak. The two-day total of 143 tornadoes from March 2 - 3 is probably an over count of about 15%, based on historical levels of over counts. This would give the March 2 - 3 outbreak around 120 tornadoes, making it the tenth largest outbreak since record keeping began in 1950. Assuming this is true, the past two tornado seasons would hold four of the top ten spots for largest tornado outbreaks in recorded history. Below are the top two-day tornado outbreaks since 1950. Several of these two-day totals were taken from outbreaks that lasted three or more days; the highest two-day period of activity was selected for this list, so that the outbreak would not be mentioned multiple times. The numbers from the 2011 outbreaks are still preliminary:

262, Apr 26 - 27, 2011
169, Apr 3 - 4, 1974
160, May 29 - 30, 2004
141, May 24 - 25, 2011
135, Jan 21 - 22, 1999
130, Apr 15 - 16, 2011
125, May 4 - 5, 2003
123, Jun 15 - 16, 1992
121, May 4 - 5, 2007
120ish, Mar 2 - 3, 2012
120, May 3 - 4, 1999


Video 1. Spectacular tornado video taken at a home in West Liberty, Kentucky outfitted with seven automatic security cameras, which captured the fury of the strong EF-3 tornado with 165 mph winds that roared overhead on March 2, 2012. The views from all the cameras are worth watching, but don't watch past 7:00, as the end of the video has three minutes of blankness at the end. According to an article at wkyt.com, the home owners, Randy and Norma Risner, took shelter in the basement, and their home survived the tornado. "You could actually feel the ground shaking and our the 11-foot basement walls were shaking, too," Norma said. The tornado destroyed their workshop (caught on camera), and another camera shows the roof of their neighbors home peel off.


Video 2. Perhaps even more impressive is video taken at a nearby pharmacy showing the West Liberty tornado destroying buildings across the street. The view from Clinic Pharmacy starts at 0:50 into this video.

The uncertain business of counting tornadoes
While there's no question that having four top-ten tornado outbreaks in just two years is highly unusual, the quality of our tornado data base is poor, and there are probably outbreaks that occurred prior to 1990 that were significantly under-counted and would have made the top ten list, had they occurred today. The number of tornadoes being reported has increased in recent decades, and this increase may be due entirely to factors unrelated to climate change:

1) Population growth has resulted in more tornadoes being reported.

2) Advances in weather radar, particularly the deployment of about 100 Doppler radars across the U.S. in the mid-1990s, have resulted in a much higher tornado detection rate.

3) Tornado damage surveys have grown more sophisticated over the years. For example, we now commonly classify multiple tornadoes along a damage path that might have been attributed to just one twister in the past.


Figure 1. Number of EF-1, EF-2, EF-3, EF-4 and EF-5 tornadoes from 1950 to 2011. The total shown for 2011 is preliminary and uses unofficial numbers, but 2011 now ranks in 2nd place behind 1973. There is not a decades-long increasing trend in the numbers of tornadoes stronger than EF-0, implying that climate change, as yet, is not having a noticeable impact on U.S. tornadoes. Data provided by Harold Brooks, NOAA/National Severe Storms Laboratory.

If we look at changes in the strongest tornadoes--EF-1, EF-2, EF3, EF4, and EF-5 twisters, the ones most likely to have a reliable long-term detection rate, due to their destructive power--we see no sign of an increasing trend in recent decades (Figure 1), even if we include 2011. However, it is difficult to make solid conclusions on how tornadoes may be changing, since the quality of the historical tornado data set is so poor. This is largely due to the fact that we never directly measure a tornado's winds--a tornado has to run over a building before we can make an EF-scale strength estimate, based on the damage. As tornado researcher Chuck Doswell said in a 2007 paper, "I see no near-term solution to the problem of detecting detailed spatial and temporal trends in the occurrence of tornadoes by using the observed data in its current form or in any form likely to evolve in the near future." Major changes in the rating process occurred in the mid-1970s (when all tornadoes occurring prior to about 1975 were retrospectively rated),and again in 2001, when scientists began rating tornadoes lower because of engineering concerns and unintended consequences of National Weather Service policy changes. Also, beginning in 2007, NOAA switched from the F-scale to the EF-scale for rating tornado damage, causing additional problems with attempting to assess if tornadoes are changing over time.


Figure 2. Thomas Hudson and the Portlight trailer in Harrisburg, Illinois.

Portlight disaster relief charity responding to the tornado disaster
The Portlight disaster relief charity has made a strong showing in tornado-devastated Harrisburg, Illinois and Henryville, Indiana. Both towns were hit by deadly EF-4 tornadoes during the February 28 - March 3 tornado outbreak. From the Portlight blog:

"Yesterday we went to Henryville, Indiana and volunteered for a few hours, mainly unloading trailers with water, canned goods, etc.

The people were in great spirit, eager to rebuild, and overall thankful that it wasn't worse than it was.

Myself, Jeremiah Moran, Blaize Edwards, and Andrew Newcomb made the 2 hour drive from Washington, Indiana.

We will be trying to get back this weekend or a couple of days next week."

An interesting sciencedaily.com article discusses how the powerful EF-4 tornado from the February 29, 2012 outbreak that devastated Harrisburg, Illinois passed through a high-density network of seismographs. "The seismograms show a strong, low-frequency pulse beginning around 4:45 a.m. on Feb. 29. Our preliminary interpretation, based on other seismic records of tornadoes, suggests that we were recording not the tornado itself, but a large atmospheric pressure transient related to the large thunderstorms that spawned the tornadoes."

I'll have a new post by Wednesday.

Jeff Masters

Tornado

Updated: 2:42 PM GMT en Marzo 13, 2012

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Tornado, hail, and torrential rains hammer Hawaii

By: JeffMasters, 5:50 PM GMT en Marzo 10, 2012

A waterspout made landfall on the Hawaiian island of Oahu Friday morning on the east shore town, becoming a rare Hawaiian tornado as it moved through the towns of Lanikai and Kailua. The twister, rated an EF-0 with winds of 60 - 70 mph, tore holes in roofs and downed trees along a 1 1/2 mile long, 20-yard wide path of damage. No injuries were reported. The same storm also brought golf ball sized hail raining down for about 45 minutes on Oahu. The islands have seen intense rains over the past week, thanks to a 1040 mb blocking high pressure system near 40°N, to the NNW of the island that forced a companion cutoff low near 25°N 165°W to stay put, bringing a series of heavy storms to the islands. Rainfall amounts over the past week have exceeded three feet in some locations. The resulting flooding forced the governor on Wednesday to declare two islands, Oahu and Kauai, disaster areas. The latest forecasts for Kauai and Oahu call for sporadic rains to continue over the weekend, followed by a drying trend during the coming week.


Video 1. On March 5, 2012, flooding rains of 3" per hour caused this creek to overflow the Loop Road on Kauai and wash away a pickup truck that tried to cross. The occupants evacuated safely.

Here are some select rainfall amounts over the past week, from the National Weather Service:

PUBLIC INFORMATION STATEMENT
NATIONAL WEATHER SERVICE HONOLULU HI
1155 AM HST FRI MAR 9 2012

...TORRENTIAL RAINS SLAM HAWAII IN THE PAST WEEK...

A SLOW MOVING FRONT BROUGHT HEAVY RAIN TO MOST ISLANDS THE PAST WEEK...AS IT INTERACTED WITH SEVERAL DISTURBANCES ALOFT. THE FOLLOWING REPRESENTS 7-DAY RAINFALL TOTALS...FROM 11 AM FRIDAY MARCH
2 THROUGH 11 AM FRIDAY MARCH 9.

KAUAI
HANALEI 45.97
WAINIHA POWER HOUSE 43.84
KAPAHI 32.66
MOUNT WAIALEALE RAINGAGE 31.32
LIHUE AIRPORT 13.59

OAHU
OAHU FOREST NWR 39.65
MOANALUA - USGS - USGS 36.42
PUNALUU STREAM - USGS 31.46
WILSON TUNNEL 25.05
LULUKU 22.25
PACIFIC TSUNAMI WARNING CENTER 20.47
HONOLULU AIRPORT 4.54

MOLOKAI
MOLOKAI AIRPORT 2.74

MAUI
PUU KUKUI - USGS 16.70
KAHULUI AIRPORT 2.34

HAWAII
HILO AIRPORT 5.97


Video 2. Damage from the March 9, 2012 tornado on Oahu.

Hawaii's tornado history
Tornadoes are rare in Hawaii. According to the Tornado History Project, only 39 tornadoes have hit the state since 1950, an average of one tornado every 1.5 years. The strongest tornadoes to hit the state occurred in 1982, when a series of three F-2 twisters struck Oahu in February and March. Those months are the most frequent months for tornadoes, with 44% of the total. No one has ever been killed in a Hawaiian tornado, but six people have been injured.

Jeff Masters

Tornado Flood

Updated: 5:53 PM GMT en Marzo 10, 2012

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Fourth warmest winter on record for the U.S.

By: JeffMasters, 2:54 PM GMT en Marzo 08, 2012

February is gone, and the non-winter of 2011 - 2012 is the history books as the fourth warmest in U.S. history, said NOAA's National Climatic Data Center yesterday. The winter average temperature of 36.8°F was just 0.4°F cooler than the warmest winter on record, the winter of 1999 - 2000. If you lived in the Northern Plains, Midwest, Southeast and Northeast, it seemed like winter never really arrived this year--27 states in this region had top-ten warmest winters. Across the U.S., only New Mexico (41st coolest) and Alaska (35th coolest) had winter temperatures colder than average. According to NOAA's Climate Extremes Index, the percent area of the U.S. experiencing extremes in warm maximum temperatures (top 10% on record) was 49 percent--the 4th highest value since the index began being computed in 1911. Jackson, Kentucky, Mount Pocono, Pennsylvania, and Trenton, New Jersey all had their warmest winter on record.


Figure 1. Contiguous U.S. temperature rankings for the winter of 2011 - 2012 (the months of December - January - February.) The 117-year period of record begins in 1895, and each state is given a ranking based on how cold this winter was, relative to the other 116 years. Thus, a ranking of 116 means it was the 2nd warmest winter on record. Image credit: NOAA's National Climatic Data Center.


Figure 2. Contiguous U.S. temperatures for winter (the months of December - January - February), from 1895 - 2012. The winter of 2011 - 2012 was the 4th warmest winter on record, behind 2000, 1999, and 1992. Winter temperatures have increased by abot 1.7°F per century (red linear trend line.) Image credit: National Climatic Data Center.

Third least snowy winter on record for the contiguous U.S.
Warm and dry conditions during the winter of 2011 - 2012 led to snow cover extent that was the 3rd lowest in the 46-year satellite record, according to data from the Rutgers Global Snow Lab. Snowfall was particularly low across parts of the West, where much of California, Nevada, and Arizona had a snowpack less than half of average. Fortunately, the West had a near-record snowpack the previous winter, so this year's lack on snow will not cause serious water availability problems during the summer. In the Upper Midwest, the lack of a winter snowpack will substantially reduce the chances of spring flooding along the Mississippi and Missouri rivers. NOAA issues their annual spring flood outlook on March 15, and it is likely to show a much lower risk of flooding compared to last year, when 1-in-100 to 1-in-500 year floods hit much of the Missouri and Lower Mississippi rivers. However, the remarkably low snow cover this winter over the Upper Midwest will allow soils to dry out much more quickly than usual, leading to increased chances of summer drought. The latest Drought Monitor map shows moderate to severe drought covering nearly all of Minnesota and Northwest Iowa; these regions are at high risk of suffering damaging drought conditions during the summer growing season.


Figure 3. State-by-state rankings of precipitation for the winter of 2011 - 2012. Four Western states had a top-ten driest winters on record, and Kansas had a top-ten wettest winter. Drought-stricken Texas, which entered the winter expecting drier than average conditions, since it was a La Niña year, lucked out, getting an unusually wet winter. Records go back to 1895. Image credit: NOAA's National Climatic Data Center.

A very mild winter for the Midwest
If you live in the Midwest, you saved a bundle this winter on heating and snow removal costs. In Minneapolis, where the low temperature falls below 0°F an average of 30 days each year, the temperature fell below zero on just two days. These days were January 18 and 19, when the low hit -1°F and -11°F, respectively. Since record keeping began in 1891, only one other winter has had so few below-zero days--the winter of 2001 - 2002. Third place is held by the winter of 1930 - 1931, with six below-zero days. Minneapolis has seen half of its usual snowfall this winter--just 22.1" as of March 7, which is 22.1" below the average of 44.2". The least snowy winter for Minneapolis occurred in the winter of 1930 - 1931, when just 14.2" of snow fell on the city.

Chicago has also seen far less snow than usual--just 19.8" as of March 7, 11.8" below their average. In a normal winter, there are 13 days with sub-zero temperatures in Chicago. The coldest it got in Chicago this winter was a relatively balmy 5°F on January 19. This is just one degree cooler than the warmest winter low temperature ever recorded in the city, which is 6°F. Here is a list of the winters in Chicago that have had no sub-zero temperatures, with the coldest temperature of the winter shown in parentheses:

1930-31 (6°F)
1959-60 (6°F)
1905-06 (6°F)
2011-12 (5°F)
1982-83 (3°F)
1938-39 (2°F)
1955-56 (2°F)
1931-32 (1°F)
1881-82 (1°F)
1936-37 (1°F)

NCDC's Dr. Deke Arndt has a two-minute video discussing the reasons for this year's warm winter. The primary factor was the position of the jet stream, which lay much farther north than usual.

I'll be back Monday at the latest with a new post.

Jeff Masters

Climate Summaries

Updated: 3:01 PM GMT en Marzo 08, 2012

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Tropical Cyclone Irina kills 72 on Madagascar

By: JeffMasters, 3:13 PM GMT en Marzo 07, 2012

Heavy rains from Tropical Cyclone Irina have killed 72 people on Madagascar and left 70,000 homeless, according to news reports. Irina never reached hurricane strength, but dumped heavy rains on the island over an extended period, February 29 - March 2. The area affected was remote, so the reports of the disaster only today reached the outside world. Irina is the deadliest tropical cyclone of 2012 thus far, and the second deadly storm to affect the island in recent weeks; Tropical Cyclone Giovanna hit the island two weeks ago as a Category 3 storm, killing 35 and leaving 240,000 homeless. Irina is expected to dissipate over cold waters southwest of Madagascar over the next day.


Figure 1. Tropical Cyclone Irina over Madagascar at 07:15 UTC March 1, 2012. At the time, Irina was a tropical storm with 65 mph winds. Image credit: NASA.

I'll have a new post on Thursday.

Jeff Masters

Hurricane

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The March 2 - 3 tornado outbreak: one EF-4, 39 deaths

By: JeffMasters, 2:40 PM GMT en Marzo 05, 2012

A blanket of snow 2 - 4 inches deep fell yesterday on the regions of Southern Indiana and Northern Kentucky pounded by deadly tornadoes on Friday, adding to the misery of survivors. The violent tornado rampage killed 39 and injured hundreds more, wreaking property damage that will likely exceed $1 billion. Hardest hit were Kentucky and Southern Indiana, which suffered 21 and 12 dead, respectively. Three were killed in Ohio, and one each in Alabama and Georgia. The scale of the outbreak was enormous, with a preliminary total of 139 tornadoes touching down in eleven states, from southern Ohio to Northern Florida. The National Weather Service issued 297 tornado warnings and 388 severe thunderstorm warnings. At one point, 31 separate tornado warnings were in effect during the outbreak, and an area larger than Nebraska--81,000 square miles--received tornado warnings. Tornado watches were posted for 300,000 square miles--an area larger than Texas.


Video 1. Spectacular video of the EF-4 tornado that devastated Henrysville and Marysville, Indiana on March 2, 2012. You can see small satellite vorticies rotating on the side of the main vortex.


Video 2. Another video of the EF-4 tornado that devastated Henrysville and Marysville, Indiana on March 2, 2012, taken from a gas station.

The deadliest and most violent tornado: an EF-4
The deadliest and most violent tornado of the March 2, 2012 outbreak was an EF-4 with winds up to 175 mph that demolished much of Henryville, Chelsea, Marysville, and New Pekin, Indiana. Ten minutes after that tornado demolished much of Henryville, a weaker EF-1 tornado hit the town. The twin tornadoes killed twelve people. The Henryville tornado was the only violent EF-4 tornado of the outbreak.



Figure 1. Radar reflectivity image (top) and Doppler velocity image (bottom) of the two tornadoes that hit Henryville, Indiana on March 2, 2012. The first (rightmost) hook echo on the reflectivity image belonged to the only violent tornado of the outbreak, an EF-4 with winds of 166 - 200 mph. Ten minutes after that tornado demolished much of Henryville, a second tornado hit the town. These tornadoes also caused severe damage to the towns of Chelsea, Marysville, and New Pekin, and killed twelve people.

At least eleven other tornadoes in the outbreak have been classified as EF-3s with winds of 136 - 165 mph. Capitalclimate.com reports that the EF-3 tornadoes that crossed three Eastern Kentucky counties were the first tornadoes that strong ever observed, since tornado records began in 1950. The deadliest of the EF-3 tornadoes hit West Liberty, Kentucky, killing eight. Here's a summary of the deadly tornadoes of the outbreak taken from Wikipedia:

EF-4, 12 deaths, Henrysville, Indiana
EF-3, 8 deaths, West Liberty, Kentucky\
EF-2, 5 deaths, East Bernstadt, Kentucky
EF-3, 4 deaths, Crittenden, Kentucky
EF-3, 2 deaths, Holton, Indiana
EF-3, 3 deaths, Peach Grove, Ohio
EF-3, 2 deaths, Blaine, Kentucky
EF-3, 2 deaths, Salyersville, Kentucky
EF-2, 1 death, Jackson's Gap, Alabama


Figure 2. Damage in West Liberty, Kentucky after the March 2, 2012 EF-3 tornado. Image taken from from a Kentucky National Guard Blackhawk helicopter, while landing in West Liberty, KY (Morgan County).


Figure 3. Radar image of the West Liberty, Kentucky EF-3 tornado of March 2, 2012, showing a classic hook echo. The tornado carved a 60-mile-long path through Eastern Kentucky, causing extreme damage in West Liberty. The tornado killed six in West Liberty and two near Frenchburg. At least 75 people were injured. It was the first EF-3 tornado in Eastern Kentucky since 1988.


Video 3. A woman prays for deliverance of West Liberty as the ominous wall cloud of the developing tornado approaches the town.

Incredibly fast-moving storms
The speed with which some of the storms moved was truly exceptional, thanks to jet stream winds of up to 115 mph that pushed the thunderstorms forward at amazing speeds. A number of the tornadoes ripped through Kentucky with forward speeds of 70 mph, and two tornado warnings in Central Kentucky were issued for parent thunderstorms that moved at 85 mph. NWS damage surveys have not yet determined if one of the tornadoes from the outbreak has beaten the record for the fastest moving tornado, the 73 mph forward speed of the great 1925 Tri-State Tornado, the deadliest U.S. tornado of all-time.


Video 4. A family gets in their car in an attempt to flee the Borden, Indiana tornado of March 2, 2012. Unless you know what you're doing, fleeing a tornado in a car can be extremely dangerous, especially when the tornadoes are moving at speeds of 50 - 70 mph, as many were doing during the March 2, 2012 outbreak. Most tornado fatalities occur in mobile homes and cars.

Largest 5-day and 2nd largest 2-day tornado outbreak for so early in the year?
The March 2 tornado outbreak spawned 128 tornadoes, according to preliminary reports as of 8 am EST March 7 from NOAA's Storm Prediction Center. An additional 11 tornadoes (preliminary) touched down on March 3, in Florida and Georgia; 3 additional tornadoes touched down on March 1 (Wikipedia does a great job tallying the stats for this tornado outbreak.) These preliminary reports are typically over-counted by 15%, but a few delayed reports will likely come in, bringing the total number of tornadoes from the March 2 - 3 outbreak to 115 - 125, propelling it into second place for the largest two-day tornado outbreak so early in the year. The top five two-day tornado outbreaks for so early in the year, since record keeping began in 1950:

January 21 - 22, 1999: 129 tornadoes, 4 deaths
March 2 - 3, 2012: 139 tornadoes (preliminary), 39 deaths
February 5 - 6, 2008: 87 tornadoes, 57 deaths
February 28 - March 1, 1997: 60 tornadoes, 10 deaths
January 7 - 8, 2008: 56 tornadoes, 4 deaths

Though the 36 tornadoes that occurred during the February 28 - 29 Leap Day outbreak were part of a separate storm system, the five-day tornado total from February 28 - March 3, 2012 is likely to eclipse the late January 18 - 22, 1999 five-day tornado outbreak (131 tornadoes) as the most prolific five-day period of tornado activity on record for so early in the year.


Figure 4. A key ingredient for tornado formation is the presence of warm, moist air near the surface, which helps make the atmosphere unstable. On the day of the March 2, 2012 outbreak, record warm air surged northwards into the tornado formation region, setting or tying daily high temperature records at 28 airports in Louisiana, Arkansas, Mississippi, Alabama, Tennessee, Kentucky, and Georgia.

Ingredients for the tornado outbreak
This year's unusually mild winter has led to ocean temperatures across the Gulf of Mexico that are approximately 1°C above average--among the top ten warmest values on record for this time of year, going back to the 1800s. (Averaged over the month of February, the highest sea surface temperatures on record in the Gulf between 20 - 30°N, 85 - 95°W occurred in 2002, when the waters were 1.34°C above average). Friday's tornado outbreak was fueled, in part, by high instability created by unusually warm, moist air flowing north from the Gulf of Mexico due to the high water temperatures there. This exceptionally warm air set record high temperatures at 28 airports in Louisiana, Arkansas, Mississippi, Alabama, Tennessee, Kentucky, and Georgia the afternoon of the tornado outbreak (March 2.) Cold, dry air from Canada moved over the outbreak region at high altitudes. This created a highly unstable atmosphere--warm, low-density air rising in thunderstorm updrafts was able to accelerate rapidly upwards to the top of the lower atmosphere, since the surrounding air was cooler and denser at high altitudes. These vigorous updrafts needed some twisting motion to get them spinning and create tornadoes. Very strong twisting forces were present Friday over the tornado outbreak area, thanks to upper-level jet stream winds that blew in excess of 115 mph. These winds changed speed and direction sharply with height,imparting a shearing motion on the atmosphere (wind shear), causing the air to spin. High instability and a high wind shear are the two key ingredients for tornado formation.


Figure 5. The other key ingredient for tornado formation is the presence of very strong winds aloft that change speed and direction sharply with height. This change of wind imparts a shearing motion on the atmosphere (wind shear), causing the air to spin. Here, we see the upper-level wind speeds at the peak of the March 2, 2012 tornado outbreak. The jet stream can be seen as the U-shaped belt of strong winds. Jet stream winds in excess of 100 mph (deep blue colors) were present over the tornado outbreak area in this analysis of data from the NOAA North American Model (NAM) from 7 pm EST March 2, 2012. Image credit: NOAA Environmental Visualization Laboratory.

Another bad year for tornadoes in the U.S.--what's going on?
Last year's tornado season was incredibly severe, and we are off to one of the worst early-season starts to tornado season on record now in 2012. However, it is too soon to ring the alarm bells on climate change being responsible for this. The tornado data base going back to 1950 doesn't show an increasing trend in strong tornadoes in recent decades. While climate change could potentially lead to an increase in tornadoes, by increasing instability, it could also decrease them, by decreasing wind shear. I'd need to see a lot more bad tornado years before blaming climate change for the severe tornado seasons of the past two years. One thing that climate change may be doing, though, is shifting the season earlier in the year. The 5-day total of tornadoes from February 28 - March 3 will probably break the record of 131 set in 1999 for the largest tornado outbreak so early in the year. Warmer winters, and an earlier arrival of spring due to a warming climate, will allow tornado season to start earlier--and end earlier. This year's early start to tornado season is consistent with what we would expect from a warming climate. I have a more extensive article on this subject that has just been published by Weatherwise magazine, and a 2008 post, Are tornadoes getting stronger and more frequent? Dr. Jonathan Martin of the University of Wisconsin-Madison is doing interesting research on the type of situation we saw with some of the recent severe tornado outbreaks, when two branches of the jet stream, the polar jet and the subtropical jet, merge to form a "superjet." In a December 2011 interview with sciencedaily.com, he said: "There is reason to believe that in a warmer climate, this kind of overlapping of the jet streams that can lead to high-impact weather may be more frequent."

I don't see any storm systems coming over the next 10 days that could cause a major tornado outbreak, though March weather is too volatile to forecast reliably that far in advance. There is a storm system expected to develop on Thursday in the Plains we will have to watch, but so far, indications are that it will not be capable of generating a major tornado outbreak.

Portlight disaster relief charity responds to the tornado disaster
The Portlight disaster relief charity reports that volunteers from colleges and churches made a strong showing in tornado-devastated Harrisburg, Illinois on Sunday. Team Rubicon and Portlight will push east to Indiana, where volunteer work is still restricted because of gas leaks and continuing SAR (search and rescue) operations.

I'll edit this post with new stats on the tornado outbreak as they become available, and have an entirely new post on Wednesday.

Jeff Masters

Tornado

Updated: 3:08 PM GMT en Marzo 12, 2012

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Violent tornado rampage in 11 states leaves 31 dead

By: JeffMasters, 5:40 PM GMT en Marzo 03, 2012

A massive tornado outbreak of stunning violence swept through the nation's midsection yesterday, spawning deadly tornadoes that killed at least 31. Hardest hit were Kentucky and Southern Indiana, which suffered 13 and 14 dead, respectively. Three were killed in Ohio, and one in Alabama. The scale of the outbreak was truly exceptional, with a preliminary total of 81 tornadoes touching down in eleven states, from southern Ohio to southern Georgia. At one point, 31 separate tornado warnings were in effect during the outbreak. An area larger than Nebraska--81,000 square miles--received tornado warnings, and tornado watches were posted for 300,000 square miles--an area larger than Texas.


Figure 1. Satellite image of the massive storm that spawned yesterday's tornado outbreak, taken at 4:55 pm EST March 2, 2012. NASA has an impressive satellite animation of the storm. Image credit: NASA/GSFC.

Incredibly fast-moving storms
The speed with which some of the storms moved was truly exceptional, thanks to jet stream winds of up to 115 mph that pushed the thunderstorms forward at amazing speeds. A number of the tornadoes ripped through Kentucky with forward speeds of 70 mph, and two tornado warnings in Central Kentucky were issued for parent thunderstorms that moved at 85 mph. If damage surveys reveal that these thunderstorms did indeed spawn tornadoes, they will set the record for fastest-moving tornadoes in recorded history. The record for the fastest moving tornado is 73 mph, set in 1925 for the great Tri-State Tornado, the deadliest U.S. tornado of all-time. Here's the text from one of the tornado warnings yesterday, featuring a storm moving at 85 mph:

BULLETIN - EAS ACTIVATION REQUESTED
TORNADO WARNING
NATIONAL WEATHER SERVICE LOUISVILLE KY
439 PM EST FRI MAR 2 2012

THE NATIONAL WEATHER SERVICE IN LOUISVILLE HAS ISSUED A

* TORNADO WARNING FOR...
FAYETTE COUNTY IN EAST CENTRAL KENTUCKY...
THIS INCLUDES THE CITY OF LEXINGTON...
JESSAMINE COUNTY IN EAST CENTRAL KENTUCKY...
EASTERN WOODFORD COUNTY IN EAST CENTRAL KENTUCKY...

* UNTIL 515 PM EST...

* AT 434 PM EST...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED A
SEVERE THUNDERSTORM CAPABLE OF PRODUCING A TORNADO. THIS DANGEROUS
STORM WAS LOCATED NEAR WILMORE...MOVING NORTHEAST AT 85 MPH.


Video 1. Short video the violent tornado that devastated West Liberty, Kentucky.


Figure 2. Radar image of the West Liberty, Kentucky tornado of March 2, 2012, showing a classic hook echo. The tornado killed at least 3 people, and devastated the downtown area.

Second largest tornado outbreak so early in the year?
NOAA's Storm Prediction Center logged 81 preliminary tornado reports from yesterday's outbreak as of noon today. These preliminary reports are typically over-counted by 15%, but more delayed reports will likely come in today, and the total number of tornadoes from the outbreak will probably be in the 80 to 90 range. This would put the March 2, 2012 in 2nd or 3rd place for the largest tornado outbreak so early in the year. The top five 2-day tornado outbreaks for so early in the year:

January 21 - 22, 1999: 129 tornadoes, 4 deaths
February 5 - 6, 2008: 87 tornadoes, 57 deaths
March 2, 2012: 81 tornadoes, 31 deaths
February 28 - March 1, 1997: 60 tornadoes, 10 deaths
January 7 - 8, 2008: 56 tornadoes, 4 deaths

Though the 36 tornadoes that occurred during the February 28 - 29 Leap Day outbreak were part of a separate storm system, the 5-day tornado total from February 28 - March 3, 2012 may eclipse the late January 1999 tornado outbreak as the most prolific 5-day period of tornado activity on record for so early in the year.


Figure 3. Damage from the Salyersville, Kentucky tornado of March 2, 2012. Damage characteristic of at least EF-3 intensity occurred. Image credit: Jon Pelton, via the NWS Jackson, KY.


Figure 4. Radar image of the Salyersville, Kentucky tornado of March 2, 2012, showing a classic hook echo of a tornado.

Slight risk of severe weather today over the Southeast U.S.
The storm system that spawned yesterday's severe weather has pushed northwards into Canada, but the trailing cold front is still spawning severe weather over Northern Florida, Southern Georgia, and surrounding states. Three tornadoes have touched down this morning in Southwest Georgia and northern Florida, causing damage but no reported injuries. NOAA's Storm Prediction Center has placed this region in their "Slight Risk" area for severe weather, two steps down from the "High Risk" forecast for Kentucky yesterday. SPC issues "High Risk" forecasts just 3 - 5 times per year, typically. Looking at the long range weather maps, I don't see any storm systems capable of causing major tornado outbreaks coming during the next 7 - 10 days. You can use our Severe Weather Page and Interactive Tornado Page to follow today's storms.


Figure 5. Team Rubicon at work during last year's tornado recovery efforts.

Portlight disaster relief charity responds to the tornado disaster
Portlight has a seasoned veteran from last year's tornado recovery efforts in Harrisburg, IL, and is looking for more people to volunteer their time. They are teaming with another disaster recovery charity, Team Rubicon, in the effort. As usual, they will be focusing efforts on the un-served, under-served and forgotten. Please visit the Portlight Disaster Relief blog to learn more. Donations are always welcome! My heartfelt sympathies and prayers go to all those affected by yesterday's destruction.

I'll be back Monday with much more information on the tornado outbreak.

Jeff Masters

Tornado

Updated: 8:11 PM GMT en Marzo 03, 2012

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High risk of a major tornado outbreak today; 13 dead from Leap Day outbreak

By: JeffMasters, 3:14 PM GMT en Marzo 02, 2012

A powerful spring storm system is gathering strength over Missouri this morning, and will track northeastward into Southern Michigan tonight. The atmosphere in the storm's warm sector, south of the the warm front and east of the cold front, is very unstable, thanks to a flow of warm, moist air from the Gulf of Mexico at the surface, and very cold, dry air aloft. A powerful jet stream with winds winds aloft blowing at 150 mph will interact with this unstable air, and the strong change of wind speed and direction with height (wind shear) associated with this jet will impart a strong twisting motion to updrafts that from in this afternoon's thunderstorms along the cold front. These are ideal conditions for tornado formation, and a large tornado outbreak with damaging long-track tornadoes is likely late this afternoon in the Ohio and Tennessee Valleys. NOAA's Storm Prediction Center has placed Central Kentucky, Northern Tennessee, and a small portion of Southern Indiana in their "High Risk" area for severe weather Friday afternoon and evening, and is warning of the possibility of long-track significant tornadoes. While the conditions are not as dangerous as those we saw in 2011 during the May 21 - 25 Joplin, Missouri and late April Southeast U.S. tornado outbreaks, the potential exists for a punishing tornado assault with many more strong and violent tornadoes than occurred during the Leap Day outbreak. A number of severe thunderstorms with damaging winds have already formed this morning along the storm's warm front, in Missouri, Indiana, and Illinois. Consult our Severe Weather Page and Interactive Tornado Page to follow the storms.


Figure 1. NOAA's Storm Prediction Center has placed Central Kentucky, Northern Tennessee, and a small portion of Southern Indiana in their "High Risk" area for severe weather Friday afternoon. This is highest level of alert.


Figure 2. NOAA's Storm Prediction Center is calling for a 30% chance of tornadoes today within 25 miles of each point in the pink shaded area. Within the hatched area, there is a 10% or greater probability of strong EF-2 and EF-3 tornadoes, or violent EF-4 and EF-5 tornadoes within 25 miles of a point.

Leap Day tornado outbreak death toll hits 13
The cleanup continues today from the round of deadly tornadoes that pounded the Midwest on Leap Day, killing thirteen people. The outbreak began on February 28, when nine confirmed tornadoes touched down. A pair of EF-2 tornadoes hit Buffalo, Missouri and Harveyville, Kansas, with each twister causing one death. Also on that day, a weak EF-0 tornado moved over open fields near Gandy, Nebraska--the first February tornado in Nebraska since record keeping began in 1950. The outbreak continued on Leap Day, February 29, with 27 more confirmed tornadoes. Hardest hit was Harrisburg, Illinois, where a violent EF-4 tornado with 180 mph killed six, injured approximately 100, and damaged 200 homes and 25 businesses. The tornado cut a path 26.5 miles long and 275 yards wide across the town, according to the NWS damage survey. The only EF-3 tornado of the outbreak hit Asherville, Missouri that day, killing one person. The other deadly tornadoes of the outbreak included an EF-2 tornado that killed one person in Cassville, MO; an EF-2 that killed two in Monterey, Tennessee, and an EF-1 that killed one person in Smithville, Tennessee. An EF-2 tornado also plowed through downtown Branson, Missouri on Leap Day, injuring 33 people. An NWS storm survey found the tornado was 400 yards wide and carved a path 22 miles long. Overall, damage from the two-day tornado outbreak will run in the hundreds of millions, and could add up to the first billion-dollar weather disaster of 2012 in the U.S. The 36 confirmed tornadoes from the outbreak make it the second largest February tornado outbreak since record keeping began in 1950. The biggest February tornado outbreak occurred on February 5 - 6, 2008, when 92 tornadoes touched down.


Figure 3. Damage at the Branson, Missouri Hilton after the Leap Day tornado. The tornado blew out or cracked windows in 219 of the hotel rooms in the 12-story/295 room Hilton Branson Convention Center, and extensively damaged three of Branson’s 50 plus theatres--Americana Theater, Branson Variety Theater and Dick Clarks’ American Bandstand Theater. Image credit: BransonRecovery Facebook page.

Portlight disaster relief charity responds to the Harrisburg, Illinois tornado
Portlight has a seasoned veteran from last year's tornado recovery efforts in Harrisburg, IL, and is looking for more people to volunteer their time. They are teaming with another disaster recovery charity, Team Rubicon, in the effort. As usual, they will be focusing efforts on the unserved, under served and forgotten. Please visit the Portlight Disaster Relief blog to learn more. Donations are always welcome!


Figure 4. Team Rubicon at work during last year's tornado recovery efforts.

Jeff Masters

Tornado

Updated: 1:44 AM GMT en Marzo 03, 2012

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Eleven deaths in tornado outbreak; new tornado outbreak likely Friday

By: JeffMasters, 3:29 PM GMT en Marzo 01, 2012

The winter of 2012 blew out like a lion yesterday, with a massive Leap Day storm that pounded the Midwest with deadly tornadoes and heavy snow. A violent EF-4 tornado with 180 mph winds tore through Harrisburg, Illinois at 4:56 am CST yesterday morning, killing six, injuring approximately 100, and damaging 200 homes and 25 businesses. The tornado cut a path seven miles long and 250 yards wide across the town, according to the NWS damage survey. Another person was killed in southwest Missouri near Buffalo when am EF-2 tornado ripped through a mobile home park late Wednesday night. Twelve others were injured in the mobile home park. Four additional deaths occurred due to tornadoes in Cassville, MO, Smithville, TN, and Monterey, TN yesterday, bringing the death toll of the two-day severe weather outbreak to eleven. An EF-2 tornado also plowed through downtown Branson, Missouri yesterday morning, injuring 33 people. The tornado blew out or cracked windows in 219 of the hotel rooms in the 12-story/295 room Hilton Branson Convention Center, and extensively damaged three of Branson’s 50 plus theaters--Americana Theater, Branson Variety Theater and Dick Clarks’ American Bandstand Theater. The Branson Landing on Lake Taneycomo and the Veterans Memorial Museum were also heavily damaged. An NWS storm survey found the tornado was 400 yards wide and carved a path 22 miles long. An EF-2 tornado also hit the small town of Harveyville, Kansas (population 275), twenty miles southwest of Topeka, at 9:03 pm Wednesday night. The tornado destroyed 40 - 60% of the structures and injured twelve, three critically. Overall, damage from the two-day tornado outbreak will run in the hundreds of millions of dollars, and could add up to be the first billion-dollar weather disaster of 2012 in the U.S.


Figure 1. Damage in Branson, Missouri after yesterday's tornado. Image credit: BransonRecovery Facebook page.

Yesterday's tornado outbreak's place in history
Yesterday was the deadliest day for U.S. tornadoes since May 24, 2011, when 18 people died in a Midwest tornado outbreak--part of the five-day outbreak that brought the deadliest U.S. tornado since 1947, the May 22, 2011 Joplin, Missouri tornado, which killed 158 people and injured 1150. The preliminary tornado total from February 28 - 29 of 2012 is 30, making it the largest February tornado outbreak since February 17 - 18, 2008, when 31 twisters touched down. Yesterday's Harrisburg, Illinois tornado was the deadliest February tornado since the February 10, 2009 EF-4 twister that struck Southern Oklahoma near Ardmore, killing eight. The deadliest February tornado in recorded history occurred on February 21, 1971, when an F-4 tornado ripped a 202-mile path through Mississippi, killing 58 people.


Figure 2. By analyzing both the rotational velocity of the storm systems (the spinning of tornadoes has high rotational velocity compared to the surrounding storms) and presence of hail, scientists at the NOAA National Severe Storms Laboratory have developed a product that approximates the track of tornadoes, shown here for the February 29, 2012 storms. Image credit: NOAA Environmental Visualization Laboratory.

Violent tornadoes in February: a rarity
Violent February tornadoes are rare in February. The Tornado History Project lists eighteen EF-4 and one EF-5 tornadoes in the U.S. during the month of February since 1950--an average of one violent February tornado every three years. Part of the reason for this is the lack of warm, unstable air so early in the year. However, this year's unusually mild winter has led to ocean temperatures across the Gulf of Mexico that are approximately 1°C above average--among the top ten warmest values on record, going back to the 1800s. Averaged over the month of February, the highest sea surface temperatures on record in the Gulf between 20 - 30°N, 85 - 95°W occurred in 2002, when the waters were 1.34°C above average. Yesterday's tornado outbreak was fueled, in part, by high instability created by unusually warm, moist air flowing north from the Gulf of Mexico due to the high water temperatures there.

Heavy snow hits Upper Midwest
The same storm system also brought the heaviest snows of the winter to portions of the Upper Midwest, which has received scant snowfall this winter. Widespread heavy snow fell in northern Wisconsin, where Mincqua recorded 18 inches. South Dakota, Central Minnesota, and Michigan's Upper Peninsula also received snow amounts in excess of a foot. The storm also brought moderate snows to Northern New England, with southern Vermont receiving more than 8 inches. The latest NOAA Storm Summary has detailed storm total accumulation info.


Figure 3. Snowfall amounts for the 3-day period ending at 7 am local time Thursday, March 1, 2012. Image credit: NOAA Southern Region Headquarters.

New tornado outbreak likely on Friday
The storm system that brought yesterday's tornadoes and snow has moved into Canada and New England, and the threat of severe weather is minimal today in the Midwest. However, a new storm system is expected to form over Missouri early Friday and track northeastward, unleashing a new tornado outbreak over Tennessee, Kentucky, Alabama, Mississippi, Indiana, and Ohio. NOAA's Storm Prediction Center has placed this region in their "Moderate Risk" area for severe weather Friday, and is warning of the possibility of long-track significant tornadoes. Consult our Severe Weather Page and Interactive Tornado Page to follow the storms.


Figure 4. NOAA's Storm Prediction Center has placed much of Tennessee, Kentucky, and portions of surrounding states in their "Moderate Risk" area for severe weather on Friday. This is one level below the highest level of alert, "High Risk."

Portlight disaster relief charity responds to the Harrisburg, Illinois tornado
Portlight is sending people into the Harrisburg, IL, area at this time in response to the tornado disaster there. They will be assessing needs there and surrounding areas. As usual, they will be focusing efforts on the un-served, under-served and forgotten. Please visit the Portlight Disaster Relief blog to learn more. Donations are always welcome!



Jeff Masters

Tornado Winter Weather

Updated: 10:05 PM GMT en Marzo 01, 2012

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About

Jeff co-founded the Weather Underground in 1995 while working on his Ph.D. He flew with the NOAA Hurricane Hunters from 1986-1990.

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