Early 2011 Atlantic Hurricane Season Forecasts

By: Dr. Jeff Masters , 6:22 AM GMT on April 07, 2011

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Hi everybody, this is Dr. Rob Carver filling in for Dr. Masters. 

A continuation of the pattern of much above-average Atlantic hurricane activity we've seen since 1995 is on tap for 2011, according to the latest seasonal forecast issued April 6 by Dr. Phil Klotzbach and Dr. Bill Gray of Colorado State University (CSU). They are calling for 16 named storms, 9 hurricanes, and 5 intense hurricanes. An average season has 10 named storms, 6 hurricanes, and 2 intense hurricanes. The new forecast is nearly identical to their forecast made in December, which called for 17 named storms, 9 hurricanes, and 5 intense hurricanes. Only six seasons since 1851 have had as many as 17 named storms; 19 seasons have had 9 or more hurricanes. The 2011 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 Caribbean is forecast to have a 61% chance of seeing at least one major hurricane (42% is average.) Five years with similar pre-season November atmospheric and oceanic conditions were selected as "analogue" years that the 2011 hurricane season may resemble: 2008, 1999, 1996, 1955, and 2006.  The first four years listed all had neutral to La Niña SST's during hurricane season, while 2006 had El Niño SST's.  The average activity for these years was 12.6 named storms, 7.8 hurricanes, and 4.8 major hurricanes.

This year, the forecasters have introduced a new statistical model for their  April forecasts.  There are four components in this model:

1. Average sea-level pressure in March around the Azores in the subtropical Atlantic.

2. The average of January through March sea-surface temperatures (SST's) in the tropical Atlantic off the coast of Africa.

3. Average sea-level pressure in February and March for the southern tropical Pacific ocean west of South America.

4. Forecasts of September's SST in the tropical Pacific using a dynamical model from the European Centre for Medium-Range Weather Forecasts (ECMWF) 

The first two components are loosely linked together.  Statistical studies have shown that a weaker subtropical high near the Azores, combined with warmer SST's off the coast of Africa in March are associated with weak winds near the surface and aloft from August to October.  This decrease in wind speeds reduces wind shear which can disrupt forming storms.  These March conditions also are associated with warmer SST's in August to October, which is also favorable for more tropical storms.   For this forecast, the first component is strongly favorable for increased hurricane activity, while the second component is weakly negative.

The last two components represent the changes in sea-surface temperature and sea-level pressure that are the El Niño-Southern Oscillation (ENSO).  Briefly speaking,  El Niño conditions (warm sea-surface temperatures) are not favorable for Atlantic hurricanes.  For more info on ENSO and hurricanes, Jeff has this article.

Using the ECMWF model as guidance (see Figure 1), the CSU group believes that SST's in the tropical Pacific will be neutral (less than 0.5°C from normal).  This would have a small negative effect on hurricane activity.  However, the tropical Pacific sea-level pressure shows that the atmosphere looks like a La Niña event is still going on.  This is strongly favorable for Atlantic hurricane activity in the CSU group's model.

Figure 1. Forecasts of El Niño conditions by 20 computer models, made in March 2011. The ECMWF forecast used by the CSU group is represented by the dark orange square.  The forecasts for August-September-October (ASO) show that 5 models predict El Niño conditions, 7 predict neutral conditions, and 5 predict a weak to moderate La Niña. El Niño conditions are defined as occurring when sea surface temperatures in the Equatorial Pacific off the coast of South America ( the "Niño 3.4 region) rise to 0.5°C above average (top red line). La Niña conditions occur when SSTs in this region fall to 0.5°C below average. Image credit: Columbia University.

How accurate are the April forecasts? While the formulas used by CSU do well in making hindcasts--correctly modeling the behavior of past hurricane seasons--their April hurricane season forecasts have had no skill in predicting the future. This year's April forecast is using a new system and has not yet produced a verified forecast.  The scheme used in the past three years successfully predicted active hurricane seasons for 2008 and 2010, but failed to properly predict the relatively quiet 2009 hurricane season. A different formula was used prior to 2008, and the April forecasts using that formula showed no skill over a simple forecast using climatology. CSU maintains an Excel spreadsheet of their forecast errors ( expressed as a mathematical correlation coefficient, where positive means a skilled forecast, and negative means they did worse than climatology) for their their April forecasts. For now, these April forecasts should simply be viewed as an interesting research effort that has the potential to make skillful forecasts. The next CSU forecast, due by June 1, is the one worth paying attention to. Their early June forecasts have shown considerable skill over the years.


Figure 2.
Accuracy of long-range forecasts of Atlantic hurricane season activity performed by Phil Klotzbach and Bill Gray of Colorado State University (colored squares) and Tropical Storm Risk, Inc. (colored lines). The CSU team's April forecast skill is not plotted, but is less than zero. 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.

2011 Atlantic hurricane season forecast from Tropical Storm Risk, Inc.

The  British  private  forecasting  firm  Tropical Storm Risk, Inc.  (TSR),   issued  their  2011  Atlantic hurricane season forecast on April 5. They are also calling for  a  very  active  year: 14. 2 named storms, 7.5 hurricanes, and 3.6 intense hurricanes. We would round that to 14 named storms, 8 hurricanes, and 4 intense hurricanes.   This  compares to their forecast issued in December of 15.6 named storms, 8.4 hurricanes,   and intense hurricanes. TSR predicts a 55%  chance  of  an  above-average  hurricane season, 28% chance of a near-normal season, and only a 17%  chance  of  a  below normal season. TSR bases their April forecast on predictions  that  sea  surface temperatures this fall in the tropical  Atlantic  will  be  above  about  0.08°C above average, and trade  wind  speeds  will  be  about 0.2  m/s  slower  than average.  The decrease in the trade wind speeds is favorable for enhanced hurricane activity, while the forecast SST's are expected to be neutral for hurricane activity.

TSR puts their skill level right next to the forecast numbers: 13% skill above chance at forecasting the number of named storms, 11% skill for hurricanes, and 10% skill for intense hurricanes. That's not much skill, and really, we have to wait until the June 1 forecasts by CSU, NOAA, and TSR to get a forecast with reasonable skill.

Rob's critiques of the April forecasts
I have to note that Jeff and I wrote this article together.  He wrote the general framework before the forecasts were issued, while I wrote the details based on the actual forecasts.  So the preceding text is a joint production.  However, I have a few observations to make that are my responsibility alone.

First, I am disappointed that the CSU group has changed forecast models only after three seasonal forecasts.  This makes it very difficult to assess the skill of the current forecast using past performance.  This is very important for forecast users, and they do it everyday.  For example, I tend to discount a forecast of rain if it comes from a source that over-forecasts rain (The boy who cried wolf problem).

In the documentation that came with the April forecast, the CSU group argue that the hindcasts show the new forecast model has skill.  However, I think hindcasts are a poor substitute for real forecasts in understanding the skill of a statistical forecast model, like that of the CSU's group.  As Jeff noted, the previous forecast model did well with the hindcasts and yet had mixed results with the actual forecasts.  This does not give me confidence that the new forecast model will be superior to the previous model.

From a philosophical viewpoint, I am inherently cautious about statistical forecast models like the one used by the CSU group.  Essentially, they look at what happened in the past and use that to predict the future.  However, for making forecasts, we assume that the relationships in space and time between the predictors (such as the average March sea-level pressure around the Azores) and the predictands (Atlantic hurricane activity) does not change as we move forward in time.  In a world with climate change, that's a tricky assumption to make.

In any event, it is customary in the meteorological community to continue running older forecast guidance models after the introduction of newer models.  This allows forecasters and forecast users to leverage their knowledge of the forecast skill of the older model and gain insight into the forecast skill of the new model.  The CSU group really should have included the forecast from the previous statistical forecast system in this forecast.     

I am uneasy with some of the methodology choices made in implementing the forecast model.  Data for the first three predictors was obtained from the Climate Forecast System Reanalysis (CFSR), NOAA's newest and most advanced reanalysis product.  However, CFSR data for 2010 and 2011 has not been released yet, so the CSU group used NCEP/NCAR Reanalysis (NNR), NOAA's first-generation reanalysis, to fill in the gaps.  Due to differences in design, resolution, etc., CFSR and NNR can have different depictions of the state of the atmosphere.  So using NNR's March 2011 average SLP instead of CFSR's could alter the forecast in unexpected ways.  It would be interesting to see how CFSR's 2010-2011 data changes the results. 

In any event, we will have to wait and see what the Atlantic hurricane season of 2011 brings.

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History channel has storm of the century on at this moment it's about 1935 hurricane in the Keys. Not trying to be coy here but shutter to think if that scenario ever plays out again. Will be cash building only in the Keys because there won't be any insurance.
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683. Jax82
Todays top google searches.

1. planned parenthood
2. government shutdown 2011
3. military pay
4. cspan
5. real housewives of new york

We sure do have a priorities straight here in the Ole US of A.

Link
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Quoting Some1Has2BtheRookie:



ecmf, What iS TORCON? The acronym nearly left Google speechless.


Do you think Google could do the same for you??
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NASA ISS Image of the Day

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Quoting Some1Has2BtheRookie:


Revenge is a dish best served cold. Keep your eyes open.


hehe hehe (What is the sign for sardonic smile?)
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Quoting Some1Has2BtheRookie:




Hi, Jeffs713.

There are some that will not allow the facts to deter them from their opinions. I have seen twincomache side with the facts before. Just keep giving him the facts and I believe he will go with the facts.

Where's Grothar?


That's a fact Jack!
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Neapolitan, I think you are missing good old Joe B's point all we have to do is evolve a little more, go back into the oceans like the dolphins and whales and we probably wouldn't have to worry about the air temp. so much. One little caveat I forgot ocean acidification. Oh well as Rossana Rossana Dana use to say never mind.
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I'm not Ike, but...

$112.65/barrel, WTI

OUCH
Member Since: August 13, 2005 Posts: 168 Comments: 26066
Wow, here comes the circular sander for Texas.
Member Since: July 11, 2006 Posts: 14 Comments: 11351


Good afternoon everyone. Nice blow-up all morning in the sw Caribbean.
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Member Since: August 7, 2010 Posts: 0 Comments: 1937
Quoting Patrap:
One from the Chief Ding-Dong @ weatherbell



"When it Comes to Climate, The Ocean, not Co2 is the Hand that Rocks the Cradle"

I'm going to send JB the latest edition of Climate for Dummies; what he's blathering about in this video is the same stuff that's been proven time and time and time again, so perhaps he needs a simple refresher on the basics. Either he's forgotten some of this stuff, or he's intentionally lying and obfuscating; it's sometimes hard to tell.
Member Since: November 8, 2009 Posts: 4 Comments: 13555

Quoting Patrap:


2011 National Hurricane Conference

April 18-22|Hyatt Regency Atlanta|Atlanta, GA

The nation's forum for education and professional training in hurricane and disaster preparedness!



Purpose of the Conference

The primary goal of the National Hurricane Conference is to improve hurricane preparedness, response, recovery and mitigation in order to save lives and property in the United States and the tropical islands of the Caribbean and Pacific. In addition, the conference serves as a national forum for federal, state and local officials to exchange ideas and recommend new policies to improve Emergency Management.

To accomplish these goals, the annual conference emphasizes:



* Lessons Learned from Hurricane Strikes.

* State of the art programs worthy of emulation.

* New ideas being tested or considered.

* Information about new or ongoing assistance programs.

* The ABC's of hurricane preparedness, response, recovery and mitigation -- in recognition of the fact that there is a continual turnover of emergency management leadership and staff.

We should all pitch in and pay for StormW to.....
Oh wait, nvm!
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Quoting RastaSteve:
If we don't get rain soon in those areas then we may see conditions similar to the Dust Bowls of the 1930's.


Luckily agriculture and general land management have come a long way since the 1930's. That's not to say that we won't have significant dust storms and wildfires, but if our high plains farmers and land managers have been doing things right then we should fare much better (in terms of soil loss) against a drought of similar severity.
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2011 National Hurricane Conference

April 18-22|Hyatt Regency Atlanta|Atlanta, GA

The nation's forum for education and professional training in hurricane and disaster preparedness!



Purpose of the Conference

The primary goal of the National Hurricane Conference is to improve hurricane preparedness, response, recovery and mitigation in order to save lives and property in the United States and the tropical islands of the Caribbean and Pacific. In addition, the conference serves as a national forum for federal, state and local officials to exchange ideas and recommend new policies to improve Emergency Management.

To accomplish these goals, the annual conference emphasizes:



* Lessons Learned from Hurricane Strikes.

* State of the art programs worthy of emulation.

* New ideas being tested or considered.

* Information about new or ongoing assistance programs.

* The ABC's of hurricane preparedness, response, recovery and mitigation -- in recognition of the fact that there is a continual turnover of emergency management leadership and staff.

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Quoting RastaSteve:


It was developed DR. Greg Forbes and it's a probability of a tornado with in 50 miles. So a 7 would indicate a 70 percent chance of a tornado with in 50 miles.


Thank you. That is very informative. And that is the real reason why I come to this blog. Many knowledgeable people here. Thanks!
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Quoting Patrap:
One from the Chief Ding-Dong @ weatherbell



"When it Comes to Climate, The Ocean, not Co2 is the Hand that Rocks the Cradle"


Obviously there must be some unrecognized genius in that statement. How did we miss it?
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TORCON

Torndao Conditions..a scale from 0-10
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Quoting emcf30:
TWC is giving a TORCON Value of 7 for a large area on Sunday, the highest so far this year. For what it is worth.



ecmf, What iS TORCON? The acronym nearly left Google speechless.
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One from the Chief Ding-Dong @ weatherbell



"When it Comes to Climate, The Ocean, not Co2 is the Hand that Rocks the Cradle"
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Quoting twincomanche:
I'm sure all the people that they owe money to or the grocery store will be happy to keep them supplied if they are not getting paid.


Should they support our troops half as much as they claim to then I think they would defer payment until the troops are paid. Hopefully, this is not going to be a long shut down, if there is a shut down at all. ... Yes, I know. The children (members of Congress) are still riding the merry-go-round. Hopefully they will tire of the nausea soon and get back down to earth.
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accuweather is a misnomer.

Just ask the "Atmospheric Avenger"

LoL
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TWC is giving a TORCON Value of 7 for a large area on Sunday, the highest so far this year. For what it is worth.
Member Since: August 7, 2010 Posts: 0 Comments: 1937
Quoting EYEStoSEA:
Be afraid...be very afraid !!



We have nothing to fear but, fear itself. Or, as Grothar once said, "I bring my own fear!".
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Quoting jeffs713:

The plains and front range didn't get much in the way of "upslop" storms this year. A lot of the systems either came across the great lakes and northern plains, or came up from the gulf - not much went across the middle, through the TX panhandle.


Exactly. This was Boulder's driest March since 1911. The Front Range can usually count on a handful of upslope snowstorms to dump 6-12" of snow a piece and we haven't gotten a single one so far this spring. I'm still holding out hope for a good upslope storm in April or even May, but if we don't get one in the next few weeks then things could get real ugly around here in terms of wildfire (it's already bad enough...)

Does anyone have a sense for what the Southwestern Monsoon season is supposed to be like this summer?
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Be afraid...be very afraid !!
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Quoting jeffs713:
Either that, or he is just biding his time, in order to plot his eventual revenge.


Revenge is a dish best served cold. Keep your eyes open.
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Quoting MrMixon:


I think the wisdom gained by age tends to thicken the skin...

Either that, or he is just biding his time, in order to plot his eventual revenge.
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Quoting MrMixon:


I think the wisdom gained by age tends to thicken the skin...



Yes,..but,..... that photo gave a whole new meaning to "thick Skin"......lol
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Quoting MrMixon:


I think the wisdom gained by age tends to thicken the skin...



I can personally testify to that. Someday, I hope to be as thick as Grothar! ..... did that come out wrong?
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Sorry in advanced Grothar
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Quoting EYEStoSEA:
Oh, Lordy, poor Grothar...not here to defend himself....lol....he's a great sport !!


I think the wisdom gained by age tends to thicken the skin...

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Quoting EYEStoSEA:
Oh, Lordy, poor Grothar...not here to defend himself....lol....he's a great sport !!




+1000
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Quoting emcf30:
No here he is at the spa



Uh, oh. I think that one will wake the sleeping giant. :-0
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Oh, Lordy, poor Grothar...not here to defend himself....lol....he's a great sport !!
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Quoting emcf30:
No here he is at the spa

LOL. (by the way, the link to that image is absurdly long... wow.)
Member Since: August 3, 2008 Posts: 16 Comments: 5885
No here he is at the spa

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Quoting emcf30:

Yeah, I think that would qualify as "significant". And OMG did they try to make a pointillistic painting with blue?
Quoting Some1Has2BtheRookie:



I agree, Jeffs.

I think I found Grothar:


I'm VERY glad he has a good sense of humor. :)
Member Since: August 3, 2008 Posts: 16 Comments: 5885
Quoting jeffs713:
I think Gro went into hibernation or something.

I know TC will side with the facts, once they are proven to be facts, as opposed to conjecture or rumor. I know quite a few people who refuse to side with facts if they disagree with their opinion or ideology, but TC isn't one of the stubborn sheeple.



I agree, Jeffs.

I think I found Grothar:

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Member Since: August 7, 2010 Posts: 0 Comments: 1937


The recent update of the 4/4/11 storm. Big numbers
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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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