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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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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Howdy,

What ever you do, don't look at the long range Long Island express at 252 out :)

Link
Member Since: June 12, 2005 Posts: 6 Comments: 8186
Quoting CaneWarning:


Well if you live in Florida like I do its of concern. Isn't that what caused Charley to go from a Cat 2 to Cat 4 very quickly?


Yes, there is a warm spot there that has affected lots of storms. Ivan, Charlie, Wilma all intensified at landfall, it allowed Katrina to continue strengthening with the eye over the glades, and helped Fay to intensify over land. I always keep a weather eye on anything that can tap it's heat.
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Quoting StSimonsIslandGAGuy:
Despite the rarity of hurricanes in Georgia, we have two hurricane superlatives that have not been equaled anywhere else in the USA. Guess what they are :)


David and Kate?
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If the system that the 18Z GFS shows actually comes to fruition, then the blog will likley go crazy.

GFS 144 hours:



GFS 147 hours:

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Quoting Tazmanian:
my blog is update if any one want too go look



window 7 will be out by oct 22nd


I don't know taz...I tried the windows 7 demo on my computer and didn't like it. Windows XP might be old and ugly, but it works for me.
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I remember Barry, if I recall not much but a rain maker. But very good example, of a early forming TS
Member Since: May 27, 2009 Posts: 0 Comments: 4438
Quoting StSimonsIslandGAGuy:
My favorite was someone who asked me that if hurricanes winds blow counterclockwise then it means they are going back in time and opening "time warp portals" in the Bermuda triangle.

No, she was not joking.



LOL!
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Alberto was another similar storm and track to Barry.Link
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my blog is update if any one want too go look



window 7 will be out by oct 22nd
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Quoting MrstormX:


Wow, what are the chances


It gets weirder. I just read all about Hurricane Alma. Thats why I was googling for info on storms affecting Georgia because I saw that her track crossed that state as well.
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Barry in 2007.That little son of a soaker!So much rain.Formed just above the Honduras close to what were watching now.
Link
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Good evening all.

Yeah that very well-defined tropical wave in the Central Pacific will be punching right into the SW Caribbean around the time that the low starts to form. Should be interesting, but we have a long time to watch this situation evolve and figure out if Florida will get rain or not.
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Illustration to comment 938

Alternating red-white arrows - upper flow
dashed red arrows - surface trough

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Quoting CaneWarning:


I'm reading that same book. Very cool.


Wow, what are the chances
Member Since: May 27, 2009 Posts: 0 Comments: 4438
Quoting MrstormX:
Right now I am reading a very fascinating book "Florida's hurricane history" By Jay Barnes and yes also Dr. Steve Lyons. Someone asked earlier about hurricanes hitting Florida in June. It is nothing I nor anyone wants to happen, but intrestinly enough a few storms have formed in the area we are discussing now that have developed and made landfall in Florida.

One that I came across was Hurricane Alma in '66, it formed tomorrow around the area we are discussing now:



Let's pray something like that does not happen!! I doubt it will but some very interesting history.


I'm reading that same book. Very cool.
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Right now I am reading a very fascinating book "Florida's hurricane history" By Jay Barnes and yes also Dr. Steve Lyons. Someone asked earlier about hurricanes hitting Florida in June. It is nothing I nor anyone wants to happen, but intrestinly enough a few storms have formed in the area we are discussing now that have developed and made landfall in Florida.

One that I came across was Hurricane Alma in '66, it formed tomorrow around the area we are discussing now:



Let's pray something like that does not happen!! I doubt it will but some very interesting history.
Member Since: May 27, 2009 Posts: 0 Comments: 4438
Quoting plywoodstatenative:
Freaky, the thing that I am worried about is that people will take what they see in here with a grain of salt and not take action should a storm come. Anyone who was involved in what StormJunkie and Presslord did last year understands that feeling, whether a person freaks or not does not matter. Its whether that person uses the information to take action and evacuate, we do not need to see the mass destruction and loss of personal property that we saw with Ike last year.


I imagine if someone finds their way to this blog they will take storm threats seriously. The general public on the other hand might not. It baffles me when I talk to educated people and they don't know the difference between a hurricane and a tornado...
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plywoodstatenative,

Here's what I'm seeing, a line of convergence is located over the SW Caribbean in 30 hrs. Due to vorticity advection, a transient low (weak low) develops and moves towards the NW Caribbean through 106-114 hrs. In the meantime, a mid-upper level trough digs over the NW Caribbean, generating moisture and a surface trough across the area. The weak transient low pulls north due to the steering flow and interacts with the associated surface trough. As the interaction occurs convection weakens the trough and a low develops NE Honduras (126 hrs). The mid-upper trough now weaken but still dominates the feature's steering flow and moves it towards the north, towards Cuba. The implications lies with the wave in the central Atlantic and the upper flow between trough-ridge.
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Freaky, the thing that I am worried about is that people will take what they see in here with a grain of salt and not take action should a storm come. Anyone who was involved in what StormJunkie and Presslord did last year understands that feeling, whether a person freaks or not does not matter. Its whether that person uses the information to take action and evacuate, we do not need to see the mass destruction and loss of personal property that we saw with Ike last year.
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Quoting plywoodstatenative:
Cane, do you understand why the location of that one and the warming of the carib concerns me?


Well if you live in Florida like I do its of concern. Isn't that what caused Charley to go from a Cat 2 to Cat 4 very quickly?
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Welcome to south Florida summer showers.
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I agree with you Cane. In some parts of the Carib. and east Atlantic below Africa have been warmer than last years temps.
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Quoting StSimonsIslandGAGuy:
I agree Canewarning--the ocean seems to be warming up very nicely!


I'm glad its not just me seeing that. Some people act like the water is just frigid or something this year.
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Cane, do you understand why the location of that one and the warming of the carib concerns me?
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The Caribbean is still warming up at a good clip.

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Quoting plywoodstatenative:
Where are the eddies located?


There is a very warm one off the west coast of Florida. That one concerns me.
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Not much dust out there now, although it looks like a new surge is coming off Africa. Link
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Where are the eddies located?
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Remember, what matters to most of us is not what happens or forms in the atlantic at this time of year. Shear values is the reason for that, however activity in the Gulf of Mexico or in the Caribbean/Gulfstream waters does concern alot of us. South Florida has been seeing non stop rain for the past 15 days, if we get a tropical storm or another no name system with a ton of tropical moisture. Then you could be seeing the repeat effect of what has happened in the Volusia county area, happening to the South Florida area both east and west coasts
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Quoting Stormchaser2007:


Its mindbogglingly that some people are that hard headed. I just read/listened to the Hurricancity update and it sounds nothing like what Drak said...


Same hear.
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Everyone keeps talking about how cool the ocean is this year compared to other years, but I look at graphics of this year compared to last year at this time and parts actually look warmer this year (at least in my opinion). Does anyone else agree or disagree? I'm just not seeing that its that much cooler than normal for this time of year.
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Quoting plywoodstatenative:
Something tells me this blog is about to get very busy very fast.

I have that feeling too. In a few days something is going to develop that will explode on this blog with users coming on here freaking out saying "Did you guys here there is this blob thats coming here!"
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Quoting plywoodstatenative:
Storm, do trolls ever give up? Seriously


Its mind boggling that some people are that hard headed. I just read/listened to the Hurricancity update and it sounds nothing like what Drak said...
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Drak, Keeper: Something interesting to think about. in the Dr.'s blog he talks about how temperatures in the Atlantic are cooler than they should be. If we are to have a quiet CV season, one would reason that the temperatures in the Atlantic would be cool. However no mention is made of the water temps in the Caribbean where activity is supposed to ramp up soon. Any thoughts?
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Blog Update
Reflector site for those at work, which now also includes Weather456, daily updates


AOI #1

AOI #2
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Storm, do trolls ever give up? Seriously
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yep some fun to
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Mrs, lets not go down that track.

Bad Memories, Bad Memories
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Quoting hurricaneseason2006:


Did you know he got it from hurricanecity morning updates. I've been seeing that pattern for several years now.


You dont give up do you?

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Something tells me this blog is about to get very busy very fast.
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Hey does anyone remember hurricane Allison from '95. It formed on June 2nd around the area of the Carribean we are talking about and went on to strike Florida.



Member Since: May 27, 2009 Posts: 0 Comments: 4438
Quoting Weather456:
700 mb curvature vorticity showing some kind of feature enhancing PV in the vicinity of the SW Caribbean, then advects it northward over the NW Caribbean. This is on time frame of 5-9 days.


Associated with 700mb vorticity advection from Panama.
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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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