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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The GOM Blob is in the Upper Levels.......nothing at the surface i can find.
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Quoting winter123:
00 gfs, 3 days out... looks like this may strengthen over land similar to storms like Danny (1997) and um E storm 2007? That formed an Eye over Kansas. Baroclinic strengthening or whatever. You can tell i'm tired so now bed for real :/



No as Weather456 was saying earlier it would be nontropical if that track played out and a frontal low.

Anyway I'm out for a while.
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NexSat Texas/Okla sector Loop
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456 you have mail
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AOI GOM
MARK
28N/88W
Member Since: July 15, 2006 Posts: 171 Comments: 53835
Taz, thats 500 mb. I use it since I always saw it the best level to get a general idea of how upper level systems affect TC steering flow. It is also reflected in the MSLP for Sept.

Member Since: July 24, 2005 Posts: 407 Comments: 19076


AOI #1

AOI #2
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00 gfs, 3 days out... looks like this may strengthen over land similar to storms like Danny (1997) and um E storm 2007? That formed an Eye over Kansas. Baroclinic strengthening or whatever. You can tell i'm tired so now bed for real :/

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storms are coming not a matter of if but when its just a matter of time and we got 179 days to go
Member Since: July 15, 2006 Posts: 171 Comments: 53835
456 dont you think by August we start seeing are 1st cold front of 2009???
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Quoting Weather456:


It is expected to continue into Jully but gone by August

July



September




ok 456 thanks that 2nd map that i was looking at for September is that the same high set up that we had in 2004??/
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Quoting Tazmanian:
this year will be more like 06 where in 06 all the cold front kep moveing down too the S and out too sea this is all most the same set up for 09 the cold fronts has not let up yet they sould all so be gone by now but there not


It is expected to continue into Jully but gone by August

July



September

Member Since: July 24, 2005 Posts: 407 Comments: 19076
448. Skyepony (Mod)
92L


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beell and Skye, I was just noticing that area as well. Quite a swirl there on the WV Good catch Skye.
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NWS Surface Look


GOM WV Loop

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this year will be more like 06 where in 06 all the cold front kep moveing down too the S and out too sea this is all most the same set up for 09 the cold fronts has not let up yet they sould all so be gone by now but there not



happy hurricane season 2006 evere one go out and in joy the nic summer we will have vary little in the way of storms this year
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444. beell
429.
Skye, I think the flare up in the NE BOC is tied to the surface trough-maybe? Along with the new convection along 95W and N of 25N on the sat loop you posted. They're in synch!

Ooops-this is 18Z NAM/850mb tomorrow morning
Photobucket
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Good evening all! Read back through all the comments and have some remarks to make, especially in regards to the disturbed weather over the Northern Gulf of Mexico.

After performing some quick analysis, don't really see much with this disturbed weather except for excellent low-level convergence. Don't really know what all the hype is about, but there currently is no surface reflection with this disturbance and appears to be entirely a mid-to-upper level system. It should move ashore as it gets drawn into a frontal system during the next 24-48 hours and bring some additional rainfall to the soaked Southeast.

Just wanted to inform everyone this evening that the CCHS Weather Center website will get a complete update sometime tomorrow as I've finished everything in regards to my brother's high school graduation and family in town. Sorry again for the inconvenience that the lack of updates may have caused.

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Quoting Weather456:
433. HurricaneKing 11:24 PM AST on June 02, 2009

Ok, I respect your point. The best we can do is monitor over the upcoming days.


Thank you.

Though I will say you're probably right. That's what would normally happen but I'm just looking at all the possibilities.
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Its a 2 Fire Eyed GOM Low..!


Ackkkkkkkkkk!

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Quoting hurricaneseason2006:


It's going to be a long season for you.


How long have you been here because I have a feeling I've been here quite a few more seasons than you.
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433. HurricaneKing 11:24 PM AST on June 02, 2009

Ok, I respect your point. The best we can do is monitor over the upcoming days.
Member Since: July 24, 2005 Posts: 407 Comments: 19076
Current GOM IR Loop
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this year will be more like 06 where in 06 all the cold front kep moveing down too the S and out too sea this is all most the same set up for 09 the cold fronts has not let up yet they sould all so be gone by now but there not
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00Z NAM
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Quoting Weather456:


True, but its also over the SE United States at the beginning (intial run). Now follow the track NE. By the time it leaves the Eastern CONUS it is frontal.


Yes but some models have it tracking across and offshore then along the gulf stream. If it does that then it may (STILL STRESSING MAY) be subtropical.
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Quoting StSimonsIslandGAGuy:
Hey Cane :) Upon reflection, I think the Texas MCC has a better chance once it gets over the Gulf of Mexico waters.


I think it and leftovers from the gulf blob are going to create another gulf blob which may be the low on the nam.
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Quoting HurricaneKing:


But at the beginning it's close to subtropical in nature. I've been watching the phase diagrams the past couple days with the lows forecast to develop in that area and they've been trending more and more tropical.


True, but its also over the SE United States at the beginning (intial run). Now follow the track NE. By the time it leaves the Eastern CONUS it is frontal.
Member Since: July 24, 2005 Posts: 407 Comments: 19076
429. Skyepony (Mod)
The red goes 12 WV looks really interesting. That lower level flair up NE side of BOC. Looks to be beginning to rotate as it moves toward the blob of upper level moisture. It still has the tropical wave around 73W to play with. Lotta land interaction. Looks moist.
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any estimates, what time will this roll on shore?
Member Since: May 27, 2009 Posts: 0 Comments: 4438
So everyone is watching the GOM blob now? It has a small window before it's onshore.
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Quoting StormJunkie:


This image is pretty much centered over this buoy. Showing continued trend to a westerly wind...There was also an anomalous temp rise just a short time ago. Unfortunately no pressure readings from this one. Any thoughts 456, HK, etc?


My thoughts are we MAY I stress MAY see something subtropicalish like Barry form in this general area within the next couple days. Ie tomorrow-early Friday. Probably closer to Friday.
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Stormjunkie,
Even my Met in Orlando who is very reliable said there was a slim chance of development in the GOM he did not rule it out, it could happen , we all should know by now there is no certainty in weather.
Member Since: July 7, 2005 Posts: 0 Comments: 5306
Is that a high on my blob?
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LOL...

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I am afraid I might wake up with a TS overhead....and I have a Cost Accounting Test in the morning. I'm sorry blob, you're going to have to stall right where you are.
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Quoting CaicosRetiredSailor:
The BLOB

that ate TEXAS


hahahaha and with that im going to bed
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Quoting Weather456:
406 & 407

You look for that kind of development when the low is forecast to stall or traverse the entire Gulf Stream like Andrea or TD 1, respectively.

The feature is expected to be a typical frontal system.


But at the beginning it's close to subtropical in nature. I've been watching the phase diagrams the past couple days with the lows forecast to develop in that area and they've been trending more and more tropical.
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Quoting Patrap:
June 2 2009



*************************************************************************************


Hurricane Cindy July 5-6 2005


Definitely some type of mid level swirl barely moving here! This really needs to be watched. Thanks for that comparison!
http://radblast-mi.wunderground.com/cgi-bin/radar/WUNIDS_map?station=LIX&brand=wui&num=6&delay=15&t ype=NCR&frame=0&scale=1.000&noclutter=0&t=1243995677&lat=29.92754936&lon=-90.10153961&label=New+Orle ans%2C+LA&showstorms=0&map.x=400&map.y=240¢erx=400¢ery=240&transx=0&transy=0&showlabels=1&se vere=0&rainsnow=0&lightning=0&smooth=0
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There is nothing at the surface it appears. Only in the upper Levels....but, its a pretty good spin for sure.
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Quoting Weather456:
406 & 407

You look for that kind of development when the low is forecast to stall or traverse the entire Gulf Stream like Andrea or TD 1, respectively.

The feature is expected to be a typical frontal system.


Hmmm.... in that case its now or never
Member Since: May 27, 2009 Posts: 0 Comments: 4438
Quoting MrstormX:
^ But right now I doubt the nhc will name it


There is nothing to name at the moment.
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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.

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