Average hurricane season foreseen by CSU, NOAA, and TSR

By: Dr. Jeff Masters , 4:45 PM GMT on June 02, 2009

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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

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1012. Levi32
During David I was....minus-12 years old lol.
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1009. aquak9
Funny, even at that young age, nothing more than 3 channels on the tv...(no cable, no remote controls) still some of us were addicted to the weather.
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# Daniel Swain Says:
June 3rd, 2009 at 3:43 pm

Confirmed golf ball sized hail near Willow Creek about 20 minutes ago. Storms may become much more widespread across NorCal late this evening as a shortwave moves up from the south. CAPEs over the Valley are incredible–nearly 3000 J/Kg. We just need a trigger–even a very small one–and it looks like we may get it between 6 and 9 PM. Stay tuned…also some strong storms in coastal SoCal. I expect to have an update later this evening.



caps here are 3,000J/kg thats un here of out here
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1006. aquak9
David...I was 15, in marching band camp in high school. Got in LOTS of trouble with the band director, cause I kept watching the clouds, instead of him.

Seems like ages ago...I guess it was.
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1004. hydrus
I was in moore haven when david hit,no eye there, but wind squalls and high water were impressive.
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Those were interesting facts about the Georgia hurricanes.

I wasnt sure how often Georgia encountered tropical weather. I was surprised when I read about Alma's track going through Georgia in 1966. I went through Georgia in 1966.I was born in Columbus,Georgia in 1966. And like the good little Army brat I am I lived there a whole six weeks. LOL

I know. I know. Representing the old folk here.

Then this afternoon I saw It Could Happen Tomorrow about a Cat 4 hitting Savannah. Chilling prospect. The officials were worried most about complacency. Yikes!

Perfect example of why you should have a plan no matter how long its been.
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1001. Ossqss
How often during formal season do we have absolutely nothing on the global scale in terms of tropical activity?

It is so slow that singularity thing may pop back up on this blog. Yikes !
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1000. KEEPEROFTHEGATE (Mod)
Quoting vortfix:
David was no small potatoes when he passed over my area in 1979.
I was in the eye for almost 45 minutes.
If I remember correctly highest gusts here were around 115 but there sere several nasty tornadoes involved with David here.
Really messed the place up.

david was my first storm i ever tracked
Member Since: July 15, 2006 Posts: 175 Comments: 54864
Quoting Weather456:
Levi, never saw the NHC as political, just conservative:

Here we clearly see a subtropical storm but Invest 92L was moving over waters near 16C and the NHC states average sea surface temperature that helps lead to subtropical cyclogenesis is 24C (75F). In every tropical weather outlook they stressed the point of the sea surface temperatures and was probably the likely cause for the lack of classification.


Yeah....I know, it's just they're so inconsistent in their policy of naming. Either they are arguing over how to properly define classification criteria or they're making decisions based on whether people will get hyped up, or something like that. It's not out of the realm of possibility.
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I think the NHC just doesn't want a repeat 2005, they have been very cautious this year. Sure 92L was subtropical but for sure 90L should have at least been a TD. They are professionals so I will let them do their thing.
Member Since: May 27, 2009 Posts: 0 Comments: 4438
Quoting MrstormX:
Wow the water looks toasty on Florida's west coast. Maybe I should fly to Tampa and then go for a swim.


The waters right off the Florida west coast are very shallow shelf waters though. It would not take very much at all to rapidly cool them. Invest 90L did it with ease.

However the rest of the gulf and the western Caribbean have been warming up quite a bit in the last week.
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Levi, never saw the NHC as political, just conservative:

Here we clearly see a subtropical storm but Invest 92L was moving over waters near 16C and the NHC states average sea surface temperature that helps lead to subtropical cyclogenesis is 24C (75F). In every tropical weather outlook they stressed the point of the sea surface temperatures and was probably the likely cause for the lack of classification.
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oooooooo boy
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Quoting Stormchaser2007:


92L is dead. Your about 2 days late...lol.


TY LOL
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Quoting MrstormX:
Wow the water looks toasty on Florida's west coast. Maybe I should fly to Tampa and then go for a swim.

I wouldn't be so sure because of this Low that is predicted to come close by next week should increase our rain chances if it forms in the Carib.
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Quoting StSimonsIslandGAGuy:
That happens a lot with hurricanes who have been over the Hispaniola shredder. Other hurricanes like Georges (1998) recovered, but never got well organized again.

However David did have a 32 mb fall in pressure after emerging from Hispaniola, which is no small thing. And there were numerous reports of hurricane force winds in Florida.

But I think the effects of Hispaniola and Florida weakened David's inner core too much.


Yeah that makes it sound like probably a combination of both Hispaniola and the frictional strain. It would make sense that Florida would get at least some hurricane-force winds but the whole system was still messed up from Hispaniola, and then frictional strain took out the surface hurricane-force winds before David made it to Georgia.
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Political Motives are a non issue in Forecasting.

To say they are is Ludicrous.

If you have issue with the NHC ,..they have a E-mail address. They are the Official Word here ALWAYS.

To demean the folks there without merit or fact does a Dis-service to the General Public at Large.


Member Since: July 3, 2005 Posts: 426 Comments: 129093
Wow the water looks toasty on Florida's west coast. Maybe I should fly to Tampa and then go for a swim.
Member Since: May 27, 2009 Posts: 0 Comments: 4438

Georges in 1998
claimed 602 Lives
Member Since: July 3, 2005 Posts: 426 Comments: 129093
Quoting Weather456:
Invest 92L was a subtropical storm at its peak, I will hold that thinking.

The Navy kept it as an archive storm but I notice this message:

NOTE: And nary an INVEST stirred, no matter where one looked.....


lol


There is no doubt that it was, it already was a STS when it got put on the SSD site. I am disappointed in the NHC for not naming it. Political reasons no doubt.
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Quoting CaneWarning:


I'm glad its not just me seeing that. Some people act like the water is just frigid or something this year.


Its not you alone. I saw the temps today and I'm amazed of the degree of warming.

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If I remember, Barry came ashore as a TS near Tyndall AFB--and was later reclassified as a Cat 1.
Member Since: June 2, 2008 Posts: 0 Comments: 157
Quoting ChrisDcane:
uhhhhhhh ?? does this invest have 40 mph look at thr tropicals/hurricanes page.


92L is dead. Your about 2 days late...lol.
Member Since: June 9, 2007 Posts: 4 Comments: 15946
Quoting ChrisDcane:
wats the weather in cozumel going to be like this weekend TY


Likely thunderstorms in the area due to the trough that will be moving into the NW Caribbean.
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Daniel Swain Says:
June 3rd, 2009 at 3:43 pm

Confirmed golf ball sized hail near Willow Creek about 20 minutes ago. Storms may become much more widespread across NorCal late this evening as a shortwave moves up from the south. CAPEs over the Valley are incredible–nearly 3000 J/Kg. We just need a trigger–even a very small one–and it looks like we may get it between 6 and 9 PM. Stay tuned…also some strong storms in coastal SoCal. I expect to have an update later this evening
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uhhhhhhh ?? does this invest have 40 mph look at thr tropicals/hurricanes page.
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I think they meant "nary".

Nary is a colloquial term for "not".

So one can rewrite:

Not an Invest stirred no matter where one look.
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Quoting ChrisDcane:
wats the weather in cozumel going to be like this weekend TY


Link
Member Since: June 9, 2007 Posts: 4 Comments: 15946
Quoting StSimonsIslandGAGuy:
Levi I thought that too, but there are no reports of hurricane winds or winds close to hurricane force on the SC side of the track either.


I was 10 during David, and the west side of the eye went over us. Home barometer reached 28.66"

Winds were never above the 40-45 mph range, and were distinctly stronger after the eye passed.


That is very strange indeed. The only other possible explanation I can think of is that passage over Hispaniola semi-permanently ruined David's core until Georgia landfall. He had an eye but it's possible there was still hidden damage in there. We still don't quite understand everything about how hurricanes work.
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wats the weather in cozumel going to be like this weekend TY
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Quoting StSimonsIslandGAGuy:
The last hurricane to cause sustained hurricane force winds in Georgia was Hurricane Kate on November 22, 1985, moving from the Gulf of Mexico.


Kate--the "Thanksgiving Hurricane" Caused some damage here in Panama City, but caused a bunch of problems in Mexico Beach.
Member Since: June 2, 2008 Posts: 0 Comments: 157
Invest 92L was a subtropical storm at its peak, I will hold that thinking.

The Navy kept it as an archive storm but I notice this message:

NOTE: And nary an INVEST stirred, no matter where one looked.....


lol
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Quoting WPBHurricane05:


And than there were none...


000
ABNT20 KNHC 032337
TWOAT
TROPICAL WEATHER OUTLOOK
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
800 PM EDT WED JUN 3 2009

FOR THE NORTH ATLANTIC...CARIBBEAN SEA AND THE GULF OF MEXICO...

TROPICAL CYCLONE FORMATION IS NOT EXPECTED DURING THE NEXT 48 HOURS.

$$
FORECASTER AVILA

Member Since: June 9, 2007 Posts: 4 Comments: 15946
Quoting homelesswanderer:


Thanks for that info on Georgia. And it is strange that no hurricane force winds were recorded.



That is odd. I think it might have something to do with David's track. He spent a lot of time right nosed up against the Florida coastline before moving inland into Georgia. That probably put great frictional strain on his wind field on the west side, and might have caused the strong winds to lift off the ground entirely and remain confined there. That would leave much lighter TS-force winds at the surface.

Something fun to ponder.

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Quoting nrtiwlnvragn:
invest_DEACTIVATE_al922009.ren


And than there were none...
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There is one other cane that struck Florida in June, that being Hurricane Agnes
Member Since: May 27, 2009 Posts: 0 Comments: 4438
invest_DEACTIVATE_al922009.ren
Member Since: September 23, 2005 Posts: 14 Comments: 11276
GOM 60 Hour Surface Current Forecast,Loop Current
Member Since: July 3, 2005 Posts: 426 Comments: 129093
Quoting StSimonsIslandGAGuy:
The last major hurricane to make landfall in GA was Oct 2, 1898.

The last hurricane to cause hurricane force sustained winds on the GA coast was Dora on the night of Sept 9/10, 1964.

The last offical hurricane to make landfall in Georgia was David on September 4th, 1979. However no land station, not even on Tybee Island recorded sustained winds even reaching 50 kts. No hurricane force winds were recorded by buoys off SC or GA either.


Thanks for that info on Georgia. And it is strange that no hurricane force winds were recorded.

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Quoting CaneWarning:


I'm reading that same book. Very cool.


I almost got that! decided on getting the new CAT 5: 1935 Labor Day Hurricane book by Thomas Knowles
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Jeff co-founded the Weather Underground in 1995 while working on his Ph.D. He flew with the NOAA Hurricane Hunters from 1986-1990.