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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Quoting twincomanche:
I thought all of this was in fun since I was directed by one far older and presumably wiser to agree with everyone.


You may drop the "presumably" with me. LOL It is good to be passionate about somethings, but I never thought that the arguments on the blog accomplished much but hard feelings between people that could be good friends. There are many on here with whom I disagree, on many subjects, but I still enjoy their company.
Member Since: July 17, 2009 Posts: 69 Comments: 25505
Quoting Grothar:


Some people do get pretty harsh on some new ones. The "troll alert" button goes on around this time of year. I hope he knows that it is only a "joke" about my age. I enjoy the ridicule. Just like a night with the in-laws. LOL Just as long as it is all in fun, I get kick out of it.


Grothar always gets stuff thrown his way lol
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Quoting twincomanche:
"Next election will be the first time I can legally vote, so I will. I just think the whole debate is stupid. There are many voters who change there minds on their party from election to election. but when it comes to internet debates, nobody every changes their stance on politics.

It just ends up being two sides arguing to two brick walls."

Out of the mouths of babes,,,,,,or a skull full of mush?

One of our youngsters.


Just sayin, hummmm :)

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Quoting DontAnnoyMe:


StormW bashing, giving new users a hard time until proven a troll, etc. Ben (13 yrs old!) asked why you always get ridiculed. I restrained myself from answering. lol


Some people do get pretty harsh on some new ones. The "troll alert" button goes on around this time of year. I hope he knows that it is only a "joke" about my age. I enjoy the ridicule. Just like a night with the in-laws. LOL Just as long as it is all in fun, I get kick out of it.
Member Since: July 17, 2009 Posts: 69 Comments: 25505
Quoting KEEPEROFTHEGATE:
andrew was a neutral storm



But El Nino's atmospheric signal was obviously still present at that point, as well as throughout the remainder of the season, given the strong vertical shear observed in the deep tropics during August-September, and also the fact that other than Andrew, every named storm had a baroclinic origin.

Hence, I don't think it's really fair to classify Andrew as a neutral hit.
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Here's a wild and crazy news story. Incredible. From the Washington post. Is being that clueless criminal?

Amid nuclear crisis, Japan’s Tepco planned new reactors
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Member Since: July 15, 2006 Posts: 169 Comments: 53308
Quoting aquak9:
"I loves me some Nutreal years!"

andrew was a neutral storm

Member Since: July 15, 2006 Posts: 169 Comments: 53308
Quoting Grothar:


What happened? I 'm too tired to go look.


StormW bashing, giving new users a hard time until proven a troll, etc. Ben (13 yrs old!) asked why you always get ridiculed. I restrained myself from answering. lol
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About the only real weather in all of the southeast U.S. this evening is a single small thunderstorm off of the SW coast of Florida. It's fading now, but put on a nice little light show for a while--a very small reminder of what's coming up in a few weeks.

Gotta love it...
Member Since: November 8, 2009 Posts: 4 Comments: 13473
Quoting Grothar:


What happened? I 'm too tired to go look.


A new girl came in, picture uploaded and all, and she starts getting teased. It makes me sad that some people do that.
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Quoting caneswatch:


You should have seen it earlier.


What happened? I 'm too tired to go look.
Member Since: July 17, 2009 Posts: 69 Comments: 25505
Quoting Grothar:


Just awoke from my nap. The blog tonight is almost as exciting of the Presidential election of 1896.


You should have seen it earlier.
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Quoting caneswatch:


Look what the wind blew in........LOL


Just awoke from my nap. The blog tonight is almost as exciting of the Presidential election of 1896.
Member Since: July 17, 2009 Posts: 69 Comments: 25505
Quoting KEEPEROFTHEGATE:
it all depends on you


Not yet!
Member Since: July 17, 2009 Posts: 69 Comments: 25505
Quoting Grothar:


It's not easy being neutral.


Look what the wind blew in........LOL
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Quoting Grothar:


WELLLLLLLL!
it all depends on you
Member Since: July 15, 2006 Posts: 169 Comments: 53308
Quoting Grothar:


It's not easy being neutral.


Tell that to the Pacific.
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Quoting xcool:
im going with neutral conditions for 2011 hurricane season...


It's not easy being neutral.
Member Since: July 17, 2009 Posts: 69 Comments: 25505
Snapshot: Japan's nuclear crisis

Following are selected developments after a massive earthquake and tsunami devastated northeast Japan and crippled a nuclear power station, raising the risk of an uncontrolled radiation leak.

--A major aftershock measuring 7.1 magnitude jolts northeast Japan on Thursday evening, but a tsunami warning is subsequently lifted. Large parts of the north experience power cuts and buildings sway strongly, even in Tokyo.

--Deputy Chief Cabinet Secretary Tetsuro Fukuyama says the risk of landslides or buildings collapsing is higher than usual.

--Japan's neighbors express alarm over radiation fallout. Trace levels of radioactive material have been detected in the air in 22 Chinese provinces, but the official Xinhua news agency says this poses no threat to health or the environment,

--After using water to cool fuel rods in Fukushina Daiichi's reactors, engineers must still pump 11.5 million liters (11,500 tonnes) of contaminated water back into the ocean as they have run out of storage space.

--The head of a U.N. Scientific body says the situation at the plant is not expected to have any serious impact on people's health. Data shows much lower levels of iodine than in the 1986 nuclear accident at Chernobyl in Ukraine.

--A top official for the U.S. Nuclear Regulatory Commission says the Commission does not believe the core of reactor no. 2 melted down.

--The coast guard says the quake shifted the seabed near the epicenter in northern Japan by a record 24 meters (79 feet).

--A total of 12,554 people were confirmed dead by Japan's National Police Agency, while 15,077 are missing as of Wednesday. A total of 162,481 households were without electricity and at least 170,000 without running water.

-- Estimated cost of damage to top $300 billion, making it the world's costliest natural disaster. The 1995 Kobe quake cost $100 billion while Hurricane Katrina in 2005 caused $81 billion in damage.

Reuters Article...
Member Since: November 8, 2009 Posts: 4 Comments: 13473
Quoting aquak9:
PCola knows me too well- - well as long as they're not wearing skimpy clothing and using the verbage of a 34 year old, and pretending to be 19? it's ok.

Ben- we tease Grothar, cause he's like 92 years old. Really. But he has a good sense of humor about it. He remembers things that most of us can only read about on Wikipedia.

When he takes his meds properly, that is.


WELLLLLLLL!
Member Since: July 17, 2009 Posts: 69 Comments: 25505
Quoting xcool:
im going with neutral conditions for 2011 hurricane season...
You should do a forecast xcool.Or have you made one all ready?.
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Quoting xcool:
im going with neutral conditions for 2011 hurricane season...


That's what it's looking like.
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405. xcool
im going with neutral conditions for 2011 hurricane season...
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Wow, I'm dumb.
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Hawaii Low??

Member Since: August 2, 2010 Posts: 21 Comments: 9737
sorry hun- I had to make a joke

that's a Nutria...and it's spelled "neutral"

just so ya know the difference between the two

:)
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Quoting aquak9:
"I loves me some Nutreal years!"

Ahhhhh real monsters!!!!
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"I loves me some Nutreal years!"

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I put the chance of seeing our first storm in may at 35%.The gulf waters are certainly warm enough to support a moderate tropical storm.And Nutreal years tend to start off quickly.So we'll see.I wouldn't get my hopes up to high.
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Private weather satellites in orbit?

Company planning biggest rocket since man on moon By SETH BORENSTEIN, AP Science Writer Tue Apr 5, 11:42 pm ET



WASHINGTON -A high-tech entrepreneur unveiled plans Tuesday to launch the world's most powerful rocket since man went to the moon.

Space Exploration Technology has already sent the first private rocket and capsule into Earth's orbit as a commercial venture. It is now planning a rocket that could lift twice as much cargo into orbit as the soon-to-be-retired space shuttle.

The first launch is slotted for 2013 from California with follow-up launches from Cape Canaveral in Florida.

Space X's new rocket called Falcon Heavy is big enough to send cargo or even people out of Earth's orbit to the moon, an asteroid or Mars. Only the long retired Saturn V rocket that sent men to the moon was bigger.

Link
Member Since: August 2, 2010 Posts: 21 Comments: 9737
Quoting Neapolitan:

The part just outside San Juan would be my guess...


What made you reach that conclusion or guess?
Member Since: August 2, 2010 Posts: 21 Comments: 9737
Quoting TomTaylor:

woah didn't realize you were that young! you aren't much older than me. I thought I was like an endangered species on this blog.


Nah, you're not, just turned 19, it'll be my first election as well. I always check in between classes, or right before I go to bed.
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Magnitude 4.0 - ARKANSAS
2011 April 07 23:11:09 UTC
Member Since: July 15, 2006 Posts: 169 Comments: 53308
Member Since: July 15, 2006 Posts: 169 Comments: 53308
Quoting Hoff511:


You can't change it without creating a new account attached to a different e-mail address.


Oh dear. Okay. Thank you.
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Unfortunately, it's hard to predict steering currents months in advance. Mid-latitude weather is much less predictable than is tropical weather. And, the mid-latitude weather patterns tend to be a lot more changeable. There are years such as last year where there tends to be a persistent trough along the East Coast that recurves most storms. However, there are other years such as 2007 where a significant trough digs in during the middle of the season and causes a different steering pattern. Early in the season, most of the systems went due west (such as Dean and Felix), and after that, most systems recurved very far east in the Atlantic.
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Well, Got to go. see you guys, next week.
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just dropping by to say hey
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I used to stay up late with my dad when I was young to watch tv, and he'd always make sure to watch the weather forecast. So my dad is the one real influence for me developing a passion for weather.

I first started following hurricanes in 2004. In 2005 my interest for hurricanes really took off--mostly because it was the biggest season in the history of the Atlantic. After 2005 though, I lost interest in hurricanes. Not really weather, I still watched the weather on tv and stuff, but I wasn't really following weather. Maybe it's because the activity was low. At any rate, 2010 kicked back up again, and I became interested again, and now here I am.
Member Since: August 24, 2010 Posts: 19 Comments: 4357
Quoting hurricaneben:


I make hurricane maps all the time. I've been tracking Hurricanes Gustav & Ike, just about every named storm in the 2008 Hurricane Season plus the very end of the 2007 season.
Same Here, The only one I missed in 2008 was Arthur because it formed in late may, and didnt last but 1 to 2 days.
2007 was another story... I tracked only the major storms(Dean, and Felix) and the storms that hit Texas.(Erin, Humberto)
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PCola knows me too well- - well as long as they're not wearing skimpy clothing and using the verbage of a 34 year old, and pretending to be 19? it's ok.

Ben- we tease Grothar, cause he's like 92 years old. Really. But he has a good sense of humor about it. He remembers things that most of us can only read about on Wikipedia.

When he takes his meds properly, that is.
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Quoting CybrTeddy:


I do.
Yup, me too.
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Quoting Jedkins01:


Yeah I voted when I got my first chance, now I'm just questioning whether I should or not anymore, I'm 20 now, was 18 then. I'll be hitting the big 21 this October 21st


1. Then the other guys win.
2. (my opinion only) If you don't vote then you have given up all right to complain because you didn't take part in the process.
3. People have died for the right to vote, and still die to this day trying to vote in some countries.

again, just my opinion
Member Since: August 22, 2008 Posts: 12 Comments: 6010

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About

Jeff co-founded the Weather Underground in 1995 while working on his Ph.D. He flew with the NOAA Hurricane Hunters from 1986-1990.