Average hurricane season foreseen by CSU, NOAA, and TSR
A near-average Atlantic hurricane season is on tap for 2009, according to the seasonal hurricane forecast issued June 2 by Dr. Phil Klotzbach and Dr. Bill Gray of Colorado State University (CSU). The CSU team is calling for 11 named storms, 5 hurricanes, and 2 intense hurricanes, and an Accumulated Cyclone Energy (ACE) 88% 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 15 named storms, 8 hurricanes, and 4 intense hurricanes per year. The new forecast is a step down from their April forecast, which called for 12 named storms, 6 hurricanes, and 2 intense hurricanes. The new forecast calls for a near-average chance of a major hurricane hitting the U.S., both along the East Coast (28% chance, 31% chance is average) and the Gulf Coast (28% chance, 30% chance is average). The Caribbean is also forecast to have an average risk of a major hurricane.
The forecasters cited several reasons for an average season:
1) Sea surface temperature (SST) anomalies in the tropical Atlantic are quite cool. In fact, these SST anomalies are at their coolest level since July 1994. Cooler-than-normal waters provide less heat energy for developing hurricanes. In addition, an anomalously cool tropical Atlantic is typically associated with higher sea level pressure values and stronger-than-normal trade winds, indicating a more stable atmosphere with increased levels of vertical wind shear detrimental for hurricanes. Substantial cooling began in November 2008 (Figure 1), primarily due to a stronger than average Bermuda-Azores High that drove strong trade winds. These strong winds increased the mixing of cool waters to the surface from below, and caused increased evaporational cooling.
2) Hurricane activity in the Atlantic is lowest during El Niño years and highest during La Niña or neutral years. This occurs because El Niño conditions bring higher wind shear over the tropical Atlantic. The CSU team expects the current neutral conditions may transition to El Niño conditions (70% chance) by this year's hurricane season. I discussed the possibility of a El Niño conditions developing this year in a blog posted Friday.
Figure 1. Change in Sea Surface Temperature anomaly between November 2008 and 2009. Most of the Atlantic has cooled significantly, relative to normal, over the past 7 months. Image credit: NOAA/ESRL.
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 slightly warm ENSO conditions, slightly below-average tropical Atlantic SSTs, and above-average far North Atlantic SSTs during April-May. Those five years were 2002, which featured Hurricane Lili that hit Louisiana as a Category 1 storm; 2001, featuring Category 4 storms Michelle, which hit Cuba, and Iris, which hit Belize; 1965, which had Category 3 Betsy that hit New Orleans; 1960, which had two Category 5 hurricanes, Ethyl and Donna; and 1959, which had Category 3 Hurricane Gracie, which hit South Carolina. The mean activity for these five years was 10 named storms, 6 hurricanes, and 2 intense hurricanes, almost the same as the 2009 CSU forecast.
How accurate are the June forecasts?
The June forecasts by the CSU team have historically offered a skill of 20 - 30% higher than a "no-skill" forecast using climatology (Figure 2). 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. This year's June forecast uses the same formula as last year's June forecast, which did quite well predicting the 2008 hurricane season (prediction: 15 named storms, 8 hurricanes, 4 intense hurricanes; observed: 16 named storms, 8 hurricanes, 5 intense hurricanes). An Excel spreadsheet of their forecast skill (expressed as a mathematical correlation coefficient) show values from 0.44 to 0.58 for their June forecasts, which is respectable.
Figure 2. Accuracy of long-range forecasts of Atlantic hurricane season activity performed at Colorado State University (CSU) by Dr. Bill Gray's team (colored squares) and Tropical Storm Risk, Inc. (TSR, colored lines). The skill is measured by the Mean Square Skill Score (MSSS), which looks at the error and squares it, then compares the percent improvement the forecast has over a climatological forecast of 10 named storms, 6 hurricanes, and 2 intense hurricanes. TS=Tropical Storms, H=Hurricanes, IH=Intense Hurricanes, ACE=Accumulated Cyclone Energy, NTC=Net Tropical Cyclone Activity. Image credit: TSR.
NOAA's 2009 hurricane season forecast
The National Oceanic and Atmospheric Administration (NOAA), issued its 2009 Atlantic hurricane season forecast on May 21. NOAA anticipates that an average season it most likely, giving a 50% chance of a near-normal season, 25% chance of an above-normal season, and a 25% chance of a below-normal season. They give a 70% chance that there will be 9 - 14 named storms, 4 - 7 hurricanes, 1 - 3 major hurricanes, and an Accumulated Cyclone Energy (ACE) in the 65% - 130% of normal range. The forecasters cited the following main factors that will influence the coming season:
1) We are in an active period of hurricane activity that began in 1995, thanks to a natural decades-long cycle in hurricane activity called the Atlantic Multidecadal Oscillation (AMO).
2) There will either be an El Niño event or neutral conditions in the Equatorial Eastern Pacific. An El Niño event should act to reduce Atlantic hurricane activity. However, our skill at predicting an Niño in late May/early June is poor, so there is high uncertainty about how active the coming hurricane season will be.
3) Cooler-than-average SSTs are currently present in the eastern tropical Atlantic. These cool SSTs are forecast to persist through into August-September-October (ASO). ASO SSTs in the eastern tropical Atlantic have not been below average since 1997. Cooler SSTs in that region are typically associated with a reduction in Atlantic hurricane activity.
Thus, they expect that even though we are in an active hurricane period, the presence of an El Niño or cool SSTs in the eastern Atlantic could easily suppress activity, making a near-average season the most likely possibility. They note that two promising computer models, the NOAA CFS model and the European Center for Medium-Range Weather Forecasts (ECMWF) Global Climate Model System 3, both forecast the possibility of a below-average hurricane season.
2009 Atlantic hurricane season forecast from Tropical Storm Risk, Inc.
The British private forecasting firm Tropical Storm Risk, Inc. (TSR) has joined the ranks of NOAA and Colorado State University in calling for near-average activity. The latest TSR forecast issued June 4 calls for 10.9 named storms, 5.2 hurricanes, 2.2 intense hurricanes, and an Accumulated Cyclone Energy (ACE) 72% of average. The storm numbers are close to the 50-year average of 10 named storms, 6 hurricanes, and 2 intense hurricanes, and are sharp reduction from their April forecast of 15 named storms, 7.8 hurricanes, and 3.6 intense hurricanes. TSR predicts a 50% chance that this season will be in the bottom 1/3 of years historically, and a 40% chance that U.S. landfalling activity will be in the lowest 1/3 of years historically. TSR gives a 32% chance of a near-normal season, and a 17% chance of a below normal season. TSR rates their skill level as 26% above chance at forecasting the number of named storms, 15% skill for hurricanes, and 19% skill for intense hurricanes.
TSR projects that 3.2 named storms will hit the U.S., with 1.3 of these being hurricanes. The averages from the 1950-2008 climatology are 3.2 named storms and 1.5 hurricanes. Their skill in making these April forecasts for U.S. landfalls is 7 - 18% above chance. In the Lesser Antilles Islands of the Caribbean, TSR projects 0.9 named storms, 0.4 of these being hurricanes. Climatology is 1.1 named storms and 0.5 hurricanes.
TSR cites two main factors for their reduced forecast: a large and unexpected cooling of sea surface temperatures in the tropical Atlantic, and warmer SSTs in the Equatorial Eastern Pacific (which might lead to an El Niño event that will bring high wind shear to the Atlantic). TSR expects faster than than normal trade winds from July - September over the Main Development Region (MDR) for hurricanes over the Atlantic (the region between 10° - 20° N from Central America to Africa, including all of the Caribbean). Trade winds are forecast to be 0.83 meters per second (about 1.7 mph) faster than average in this region, which would create less spin for developing storms, and allow the oceans to cool down, due to increased mixing of cold water from the depths and enhanced evaporational cooling. TSR forecasts that SSTs will cool an additional 0.3°C compared to average over the MDR during hurricane season.
Air France crash
The Air France Flight 447 A330 aircraft that disappeared over the mid-Atlantic Ocean yesterday definitely crossed through a thunderstorm complex near the Equator, according to a detailed meteorological analysis by Tim Vasquez. He concludes that "the A330 would have been flying through significant turbulence and thunderstorm activity for about 75 miles (125 km), lasting about 12 minutes of flight time" but that "complexes identical to this one have probably been crossed hundreds of times over the years by other flights without serious incident". See also the excellent CIMSS satellite blog for more images and analysis of the weather during the flight.
Invest 92
NHC is tracking a storm near the Azores Islands (Invest 92L) that is probably the remnants of the core of an extratropical cyclone that closed off some warm air at the center. The system has developed some heavy thunderstorm activity near its center, making this a hybrid storm. However, with ocean temperatures near 62°F (16°C), this storm has little chance of becoming a named subtropical storm.
Jeff Masters
Reader Comments
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Some of the guppies are stil in service a second "generation"/refurbed model is loaded with meterologial instruments and a bunch of other stuff studying upper atmosphere related issues. A couple others are still performing their original duties of transportation. I believe all of them are now jet powered though. I see them fly into and out of Ellington Field a few times a year
As for the GOM feature itself, I'm not quite sure to make of it on radar. It is showing some persistence, but the storm cells themselves look to be feeding off each other, rather than feeding off the water's heat content. Looks more baroclinic than tropical.
Link
Ellington is actually a NASA terminal... that is one of their main airports from what I understand and they actually store some of the planes there.
Holy crap.
Andrew was technically a cape verde style, but only started getting organized north of Hispaniola...
Its still over 16C water, though.
Amazing, huh? These extratropical/subtropical systems are pretty complex.
Just takes 1 over your community. Have a great evening. Adrian
No kidding. I always enjoy watching low pressure systems spin up.
True! 1992 is a perfect example
Agreed. Ask anyone that has been hit by one recently.
Galveston had not had a direct hit since 1983 until Ike made landfall. Ike changed the landscape, and many people's views on hurricanes.
I will mention that not *everything* a hurricane does is bad. They can also end droughts, and they have a tendency to bring people back to what is important. Helping each other, and knowing your neighbors. (Portlight is an example).
Before Ike, there were neighborhoods where hardly anyone really knew their neighbors. After Ike, entire streets would gather together, and basically have a cookout, with each family donating something to the group, just so nothing spoiled. Those same families did something with each other many of them had not done in years. They talked. Ike left a swath of destruction that was incredible to see. But Ike also forged some bonds that will never be broken.
That looks like a big storm even if it is weak.
Do you really think I care about that? The models take it right over my house.
2009hurricane - Are we really gonna have an uber slow season?
My last prediction (May 2nd):
12-15 Tropical Depressions
8-12 Tropical Storms
7 - 9 Hurricanes
1 Major Hurricane
0 Cape Verde Cyclones
Original Prediction (Predicted April 15th):
15-17 Tropical Depressions
12-14 Tropical Storms
5-9 Hurricanes
0-1 Major Hurricane
2 Cape Verde Cyclones
I'm trying to figure out why the ghost hurricane looks fairly strong over by the Turks and Caicos, but suddenly weakens before going through the Bahamas.
Thats interesting... Yesterday the GFS was showing an intense storm in the Gulf of Mexico around this same forecast time period.. I wouldn't even bet on that storm forming at least until more runs of the GFS come in.. Thats at least two weeks away.. So alot of time to watch it. This period, however conicides with the time that an area of rising motion is expected to move from the west pacific to the atlantic.. Wouldn't be suprised to see some sort of development.
Thanks for telling me. I think its too organised to be that weak.
*Clicks Tropical Weather*
*Sees the picture of current tropical weather*
"What the [edit]?!?!?"
Why did they classify 92L as such if it's that far north?
Similar to a Polar Low
Theirs "lower level convergence" there.
If 92L were declared, my mind would explode from the mind-boggling-ness of it.
I don't remember try the SSD.
Currently its at ST3.0
FERNANDO DE NORONHA, Brazil – Brazilian military planes found a 3-mile (5-kilometer) path of wreckage in the Atlantic Ocean, confirming that an Air France jet carrying 228 people crashed in the sea, Defense Minister Nelson Jobim said Tuesday. Jobim said the discovery "confirms that the plane went down in that area" hundreds of miles (kilometers) from the Brazilian archipelago of Fernando de Noronha.
He said the strip of wreckage included metallic and nonmetallic pieces, but did not describe them in detail. No bodies were spotted in the crash of the Airbus in which all aboard are believed to have died.
The discovery came just hours after authorities announced they had found an airplane an airplane seat, an orange buoy and signs of fuel in a part of the Atlantic Ocean with depths of up to three miles (4,800 meters).
Link
If it deserves classification, it should be classified- doesn't serve anyone any good not classifying it-
Also, thought, if this is classified, then France or Britain could become the second country to have a tropical system make landfall on.
"ok a sub-storm formed in 62 degree water in the north Atlantic first week of June and wouldn't you think the season will be like 05' or worse?! why are the numbers so low shouldn't you revise your forecast? are you not confident on this season? wouldnt you say this is a precursor of a horrific season? what is wrong with you people?
LOL...
That would be going too far, IMO. The only reason this is getting attention is because its the start of hurricane season. Lows will spin up that are stronger than this during the winter... but they don't get named. (nor should they be)
I guess you haven't seen the latest satellite images...
After a storm like this hit north carolina several years ago there was a great debate on what kind of subtropical storms should be named. It looked just like this for about a day and a half as it moved northeast out to sea before it merged with a larger low. They decided that if it had lasted longer they would have named it.
and why should they not be???
There is a trough running SW to NE through the BOC/GOM. Currently there is no associated low, but there is a little surface vorticity at the southern most end. There is some disorganized vorticity in the very upper levels. This trough should be moving NW over the next day or so.
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