CSU predicts a very active hurricane season: 16 storms, 9 hurricanes
A very active Atlantic hurricane season is on tap for 2011, according to the seasonal hurricane forecast issued June 1 by Dr. Phil Klotzbach and Dr. Bill Gray of Colorado State University (CSU). The CSU team is calling for 16 named storms, 9 hurricanes, and 5 intense hurricanes, and an Accumulated Cyclone Energy (ACE) 166% of average. Between 1950 - 2000, the average season had 10 named storms, 6 hurricanes, and 2 intense hurricanes. But since 1995, the beginning of an active hurricane period in the Atlantic, we've averaged 14 named storms, 8 hurricanes, and 4 intense hurricanes per year. The new forecast is identical to their April forecast. The forecast calls for a much above-average chance of a major hurricane hitting the U.S., both along the East Coast (48% chance, 31% chance is average) and the Gulf Coast (47% chance, 30% chance is average). The risk of a major hurricane in the Caribbean is also high, at 61% (42% is average.)
The forecasters cited four main reasons for an active season:
1) Neutral to weak La Niña conditions are expected during the most active portion of this year's hurricane season (August-October). This should lead to average to below average levels of vertical wind shear.
2) Above average May sea surface temperatures in the tropical Atlantic.
3) Below average surface pressures during May in the tropical Atlantic.
4) We are in the midst of a multi-decadal era of major hurricane activity, which began in 1995. Major hurricanes cause 80-85 percent of normalized hurricane damage.
Analogue years
The CSU team picked five previous years when atmospheric and oceanic conditions were similar to what we are seeing this year: neutral to weak La Niña conditions in the equatorial Eastern Pacific, and above-average tropical Atlantic and far north Atlantic SSTs during April - May. Those five years were 2008, which featured Hurricane Ike and Hurricane Gustav; 1996, which had two hurricanes that hit North Carolina, Fran and Bertha; 1989, which featured Category 5 Hurricane Hugo; 1981, a very average year with 12 named storms, 7 hurricanes, and 3 intense hurricanes; and 1951, a year that featured 6 major hurricanes. The mean activity for these five years was 12 named storms, 8 hurricanes, and 4 intense hurricanes.
How accurate are the June forecasts?
The June forecasts by the CSU team between 1998 and 2009 had a skill 19% - 30% higher than a "no-skill" climatology forecast for number of named storms, number of hurricanes, and the ACE index (Figure 1). This is a decent amount of skill for a seasonal forecast, and these June forecasts can be useful to businesses such as the insurance industry and oil and gas industry that need to make bets on how active the coming hurricane season will be. Unfortunately, the CSU June 1 forecasts do poorly at forecasting the number of major hurricanes (only 3% skill), and major hurricanes cause 80% - 85% of all hurricane damage (normalized to current population and wealth levels.) This year's June forecast uses a brand new formula never tried before, so there is no way to evaluate its performance. An Excel spreadsheet of their forecast skill (expressed as a mathematical correlation coefficient) show values from 0.41 to 0.62 for their June forecasts made between 1984 and 2010, which is respectable.
Figure 1. Comparison of the percent improvement over climatology for May and August seasonal hurricane forecasts for the Atlantic from NOAA, CSU and TSR from 1999-2009 (May) and 1998-2009 (August), using the Mean Squared Error. Image credit: Verification of 12 years of NOAA seasonal hurricane forecasts, National Hurricane Center.
Figure 2. Comparison of the percent improvement in mean square error over climatology for seasonal hurricane forecasts for the Atlantic from NOAA, CSU and TSR from 2001-2010, using the Mean Square Skill Score (MSSS). The figure shows the results using two different climatologies: a fixed 50-year (1950 - 1999) climatology, and a 2001 - 2010 climatology. Skill is poor for forecasts issued in December and April, moderate for June forecasts, and good for August forecasts. Image credit: Tropical Storm Risk, Inc.
TSR predicts 25% more activity than normal
Expect the Atlantic hurricane season to be about 25% more active than usual, the British private forecasting firm Tropical Storm Risk, Inc. (TSR) said in their pre-season forecast issued on May 24. TSR calls for 14.2 named storms, 7.6 hurricanes, 3.6 intense hurricanes, and an Accumulated Cyclone Energy (ACE) of 124, which is 22% above average. Their May 24 forecast numbers are very close to their previous forecast issued in April. TSR predicts a moderate 55% chance that activity will rank in the top 1/3 of years historically, and a 59% chance that U.S. landfalling activity will be above average. TSR rates their skill level as 16-25% higher than a "no-skill" forecast made using climatology, though an independent assessment by the National Hurricane Center (Figure 1) gives them somewhat lower skill numbers.
TSR projects that 4.4 named storms will hit the U.S., with 1.9 of these being hurricanes. The averages from the 1950-2010 climatology are 3.1 named storms and 1.5 hurricanes. They rate their skill at making these June forecasts for U.S. landfalls at 7 - 11% higher than a "no-skill" forecast made using climatology. In the Lesser Antilles Islands of the Caribbean, TSR projects 1.3 named storms, 0.6 of these being hurricanes. Climatology is 1.1 named storms and 0.5 hurricanes.
TSR cites two main factors for their forecast of an active season:
1) Their model predicts that sea surface temperatures will be 0.11°C warmer than average in August and September over the Main Development Region (MDR) for Atlantic hurricanes. They define this as the area between 10°N and 20°N, between the coast of Africa and Lesser Antilles Islands (20°W and 60°W). It is called the Main Development Region because virtually all African waves originate in this region. These African waves account for 85% of all Atlantic major hurricanes and 60% of all named storms. When SSTs in the MDR are much above average during hurricane season, a very active season typically results (if there is no El Niño event present.)
2) Their model predicts slower than normal trade winds in August and September over the Main Development Region (MDR). Trade winds are forecast to be 0.19 meters per second (about 0.4 mph) slower than average. This would create more spin for developing storms, and allow the oceans to warm up, due to reduced mixing of cold water from the depths and lower evaporational cooling.
FSU predicts a very active hurricane season: 17 named storms
The Florida State University (FSU) Center for Ocean-Atmospheric Prediction Studies (COAPS) issued their third annual Atlantic hurricane season forecast today. This year's forecast calls for a 70% probability of 14-20 named storms and 8-10 hurricanes. The mean forecast is for 17 named storms, 9 hurricanes, and an accumulated cyclone energy (ACE) of 163. They cite warm tropical North Atlantic sea surface temperatures, a weakening of La Niña conditions, and the ongoing positive phase of the Atlantic Multi-decadal Oscillation as the major factors influencing their forecast.
Other seasonal forecasts
The UK Met Office's Glosea4 model is predicting a moderately more active season than normal, with 13 named storms and a ACE index of 151. The Cuba Institute of Meteorology is calling for 13 named storms and 7 hurricanes. NOAA predicts 15 named storms, 8 hurricanes, and 4.5 intense hurricanes. Pennsylvania State University predicts 16 named storms.
A surprise tropical disturbance for Florida
The Atlantic hurricane season is officially underway, and Mother Nature appears to be taking her cue from the calendar, as we have a surprise storm off the coast of Florida that is a threat to develop into a tropical depression later this week, after it crosses Florida into the Gulf of Mexico. An cluster of thunderstorms called a Mesoscale Convective System (MCS) pushed across southern New England early yesterday, emerged over the ocean, and rotated clockwise towards Florida, steered by a large high pressure system centered over Kentucky. The center of the disturbance stayed over the warm waters of the Gulf Stream, a region of low pressure developed, and intense thunderstorms began to build yesterday afternoon. Early this morning, the National Hurricane Center (NHC) designated the disturbance Invest 93L, and gave it a 10% chance of developing into a tropical depression. At 8am EDT, they upped those chances to 30%. Invest 93L is becoming increasingly organized, with Melbourne, Florida radar showing the beginnings of some rotation, with a solid band of heavy rain on the southwest side of the disturbance. The pressure and winds have leveled out at Buoy 41012, 40 nm ENE of St. Augustine, Florida. Winds peaked at 19 mph, gusting to 22 mph, at 10:50am EDT. Satellite imagery shows a small but intensifying region of thunderstorms. Sea surface temperatures (SSTs) are about 26°C (79°F) off the east coast of Florida, which is just warm enough to support formation of a tropical depression, and about 0.5°C above average. Wind shear is a low 5 - 10 knots, and it is likely that 93L will continue intensifying until it makes landfall over Central Florida this afternoon. A 50-mile wide swath of Florida from Daytona Beach to just north of Tampa can expect 1 - 3 inches of rain from 93L as it tracks over the state this afternoon and tonight. A Windsat pass this morning did not show a closed circulation, and I doubt 93L has enough time to develop into a tropical depression before landfall in Florida. The coast between Daytona Beach and Cocoa Beach could see wind gusts of 25 - 35 mph this afternoon, though.
Figure 3. Afternoon radar image of 93L from the Melbourne, Florida radar.
Fate of 93L once in the Gulf of Mexico
Since 93L is expected to continue its rapid west-southwest motion at 15 - 20 mph through Thursday, it will cross the Florida Peninsula in about 12 hours and emerge over the Gulf of Mexico early Thursday morning. It is possible that the passage over Florida will greatly disrupt 93L, since it is such a small system. I give a 40% chance that the storm will see its peak strength this afternoon, and not significantly regenerate over the Gulf of Mexico. However, the latest SHIPS model forecast predicts that wind shear will remain low to moderate, 5 - 15 knots, as 93L moves westwards over the Gulf of Mexico Thursday and Friday. SSTs in the Gulf are about 27°C (81°F), 0.5 - 1.0°C above average, and it is possible that 93L could gain enough strength to become Tropical Depression One as it crosses the Gulf. Since 93L will be moving parallel to the coast a short distance offshore, it is difficult to predict where the storm might make a second landfall, since a slight change in heading will make a large difference in landfall location. I don't expect widespread heavy rains from 93L along the Gulf Coast, since the storm is so small, but some locations close to the coast could receive 2 - 4 inches as 93L brushes by. Heavier rains are possible at the eventual landfall location. Since 93L is so small, the computer models are having trouble seeing the system, and are not very helpful forecasting the behavior of the storm over the Gulf of Mexico. The Hurricane Hunters are on call to fly into 93L Thursday afternoon at 2pm EDT, if necessary.
Central Caribbean disturbance
Moisture and heavy thunderstorm activity continues to slowly increase in the region between Central America and Jamaica, and wind shear is falling. With wind shear now 20 - 30 knots, we can expect this disturbance to show increased organization today, and recent satellite images show the beginnings of a surface circulation trying to get going about 100 miles off the coast of Northeast Nicaragua. All of the computer models predict that an area of low pressure will form in this region by Thursday, and this low will have the potential to develop into a tropical depression late this week or early next week. A surge of moisture accompanying a tropical wave currently south of Hispaniola may aid development when the wave arrives in the Western Caribbean on Thursday. Water temperatures in the Central Caribbean are about 1°C above average, 29°C, which is plenty warm enough to support development of a tropical storm. Residents of Jamaica, Cuba, the Cayman Islands, Haiti, Honduras, and Nicaragua should anticipate the possibility that heavy rains of 2 - 4 inches may affect them Thursday through Saturday this week.
Figure 4. Satellite image of the Central Caribbean disturbance.
Catch my intro to the 2011 hurricane season on Internet radio
I'll be discussing the coming hurricane season on our Internet radio show, the Daily Downpour, tomorrow (Thursday) at 4:30pm EDT. Fellow wunderground meteorologists Shaun Tanner and Tim Roche will be hosting the show. We'll talk about the latest model runs, hurricane research, modeling accuracy, and hurricane climatology, and answer any questions listeners email in or call in. The email address to ask questions is broadcast@wunderground.com. Welcome to the hurricane season of 2011!
Jeff Masters
Reader Comments
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Could develop once it emerges over the GOM, upper level winds and wind shear is favorable.
Could you give me the link for that site? I always used to use it, but don't have it on my laptop favorites.
Thanks.
1. The Monsoon trough has nosed into the area
2. A tropical wave is bringing a lot of moisture from the East and is about to enter the area
3. Shear has continued to fall down there and a high is now trying to establish itself overhead. Conditions aloft over the low are now in fact fairly reasonable for development and should continue to improve over the next 24 hours.
Or the famous storm that never got named last year..remember the little bugga that hit South Louisiana...many people thought it was a TD just before landfall
It needs to slow down once it emerges over water. Just the speed of its movement can cause shear, better known as "speed shear." Pretty stout upper ridge located over the South Central US.
Oh believe me I want it to, I love little shore-hugging Tropical Storms (Which is why I used to have one of those as my avatar) but I doubt it will happen.
Tropical Depression Invest? Isn't that a borderline between TD and an invest?
Yeah, I think it was even smaller then 93L.
maybe D or E we will have to wait until its in the GOM
93L .
CapeCanaveral got the thick of the storm.
Why do these ATCF coordinates appear to be FAR more behind the actual track than the 1hour-late of last year? And IF they are more than 6hours late as it appears, why does NHC keep having to alter the previous set of coordinates?
All Active Year
Atlantic
93L.INVEST
East Pacific
Central Pacific
West Pacific
90W.INVEST
Indian Ocean
Southern Hemisphere
Well i don't think it will become anything huge like a moderate TS or anything the water temps for that kind of rapid intensification just aren't there but i wouldnt be surprised if we end up seeing a TD out of this
We should be greeted tomorrow morning with some fresh 94L model runs. I can't imagine them waiting much longer, as you say and I concur, the stage is set.
I think it would be a she, assuming that pre 94L (Caribbean AOI) doesn't develop before 93L.
Hello everyone!!!
I am not banking on a named system at this point, but ok, "she"......... :)
Yes sir, Hurricane Humberto...
Pre 94L may be named, and as Kman mentioned, all the ingredients are falling into place, looks like we have a close race to see who becomes a depression first then later on a named storm.
B
Yeah.
And I had not noticed the trough...
You will get wet, whatever happens!
93L Rainbow Floater Loop
We hope for the best and prepare for the worst,
All the familiar faces have shown up this year,
Some to debate and argue and others to cheer,
We wake on day 1 with 93L on the map,
No time to rest lets get on with this crap,
Ctriticizing the experts will be the theme of the day,
And the term 'downcasting' will get lots of play,
If that thing gets to the Gulf with any swirl at all,
Hundred bucks says it's a direct NOLA landfall,
Now the NHC gives the Carrabean Blob a mention,
Ok 2011 Season you've got my attention,
I just hope it's a sign of the season ahead,
So I can look forward to all the DOOM & DREAD,
But don't get too excited and try to remember,
Its a long way to go till the end of November,
And I hate to bring bad news but inform you I must,
No matter what happens the seasons already a BUST.
Happy Hurricane Season 2011 folks :-)
NOAA's NowCoast
May 13, 2011
By: Bruce Berry
In preparation for a hurricane season that some forecasts say could be busy, Florida's primary homeowners insurance company has voted to borrow funds to enhance its reserves.
The board of governors for Citizens Property Insurance Corporation - which is run by the state and covers 1.3 million Florida homeowners - has voted to borrow $900 million through a bond issuance, according to various reports. An additional $500 million in private market reinsurance will be purchased to ensure the company will be able to pay out claims to Florida homeowners in the event of major losses due to hurricanes.
Officials with the group told the Sunshine State News the measures were needed in part because legislation that would have led to a increase in property insurance rates was batted down in the state legislature.
"We all had great hopes that the legislative session was going to provide us the ability to raise our rates to the appropriate levels," chairman James Malone told the source.
Lawmakers had debated the merits of raising rates for months but settled on a proposal that gives homeowners insurance companies more power to investigate fraudulent sinkhole claims. Legislators hope the measure would encourage more private insurers to enter the market and relieve CPIC of its coverage load.
I believe the legislature limited the amount of time you have to file a new claim, a supplemental to an already open claim, or reopening of a closed claim to 3 years from the date of the actual event. This law went into effective today.
Actually I was looking for info myself.
Consider it "Peer Reviewed" as of now.
I love the last line!
Good Stuff.
296
WFUS51 KBOX 011928
TORBOX
MAC011-013-015-012000-
/O.NEW.KBOX.TO.W.0002.110601T1928Z-110601T2000Z/
BULLETIN - EAS ACTIVATION REQUESTED
TORNADO WARNING
NATIONAL WEATHER SERVICE TAUNTON MA
328 PM EDT WED JUN 1 2011
THE NATIONAL WEATHER SERVICE IN TAUNTON HAS ISSUED A
* TORNADO WARNING FOR...
SOUTH CENTRAL FRANKLIN COUNTY IN WESTERN MASSACHUSETTS...
NORTHWESTERN HAMPDEN COUNTY IN WESTERN MASSACHUSETTS...
WESTERN HAMPSHIRE COUNTY IN WESTERN MASSACHUSETTS...
THIS INCLUDES THE CITIES OF...NORTHAMPTON...AMHERST...
* UNTIL 400 PM EDT
* AT 327 PM EDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED A
SEVERE THUNDERSTORM CAPABLE OF PRODUCING A TORNADO NEAR CHESTER...
OR 11 MILES WEST OF NORTHAMPTON...MOVING EAST AT 40 MPH.
* SOME LOCATIONS IN THE WARNING INCLUDE...CHESTERFIELD...GOSHEN...
WESTHAMPTON...SOUTHAMPTON...WILLIAMSBURG...EA STHAMPTON...
HATFIELD...WHATELY...HADLEY...SOUTH HADLEY AND GRANBY.
WHEN A TORNADO WARNING IS ISSUED BASED ON DOPPLER RADAR...IT MEANS A
TORNADO MAY ALREADY BE ON THE GROUND OR IS EXPECTED TO DEVELOP
SHORTLY. TAKE COVER NOW! MOVE TO AN INTERIOR ROOM ON THE LOWEST FLOOR
OF A STURDY BUILDING. AVOID WINDOWS. IF IN A MOBILE HOME...A VEHICLE
OR OUTDOORS...MOVE TO THE CLOSEST SUBSTANTIAL SHELTER AND PROTECT
YOURSELF FROM FLYING DEBRIS.
A TORNADO WATCH REMAINS IN EFFECT UNTIL 800 PM EDT WEDNESDAY EVENING
FOR NORTHERN CONNECTICUT AND MASSACHUSETTS AND SOUTHERN NEW HAMPSHIRE
AND CENTRAL RHODE ISLAND.
&&
LAT...LON 4239 7303 4239 7302 4243 7300 4244 7299
4245 7251 4222 7247 4221 7302 4225 7301
4230 7301 4231 7303
TIME...MOT...LOC 1928Z 264DEG 33KT 4233 7288
$$
--
Oh boy.....
Oh man...Not even one day?
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