NOAA predicts an active Atlantic hurricane season: 15 named storms, 8 hurricanes

By: Dr. Jeff Masters , 4:08 PM GMT on May 19, 2011

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The National Oceanic and Atmospheric Administration (NOAA) issued its 2011 Atlantic hurricane season forecast today. NOAA forecasts a very active and possibly hyperactive season. They give a 65% chance of an above-normal season, a 25% chance of a near-normal season, and just a 10% chance of a below-normal season. NOAA predicts a 70% chance that there will be 12 - 18 named storms, 6 – 10 hurricanes, and 3 - 6 major hurricanes, with an Accumulated Cyclone Energy (ACE) 105% - 200% of the median. If we take the midpoint of these numbers, NOAA is calling for 15 named storms, 8 hurricanes, 4.5 major hurricanes, and an ACE index 152% of normal. A season with an ACE index over 165% is considered "hyperactive." An average season has 10 – 11 named storms, 6 hurricanes, and 2 intense hurricanes. Hurricane seasons during 1995-2010 have averaged about 15 named storms, 8 hurricanes, and 4 major hurricanes, with an ACE index 151% of the median. NOAA classifies 11 of the 16 seasons since 1995 as above normal, with eight being hyperactive. Only five seasons since 1995 have not been above normal, which include four El Niño years (1997, 2002, 2006, and 2009), and the 2007 season.

The forecasters cited the following main factors that will influence the coming season:

1) Above-average sea surface temperatures (SSTs) are expected in the hurricane Main Development Region (MDR), from the Caribbean to the coast of Africa between between 10°N and 20°N. SSTs in the MDR during April were about 0.5°C above average, the 14th warmest April SSTs in the past 100 years. This is far below last year's record 1.4°C anomaly, but still plenty warm enough to help drive above-average Atlantic hurricane activity. Long-range computer forecast models are predicting a continuation of these above-average SSTs through the peak part of hurricane season.

2) 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): "During 1995-2010, some key aspects of the tropical multi-decadal signal within the MDR have included warmer than average SSTs, reduced vertical wind shear and weaker easterly trade winds, below-average sea-level pressure, and a configuration of the African easterly jet that is more conducive to hurricane development from tropical waves moving off the African coast. Many of these atmospheric features typically become evident during late April and May, as the atmosphere across the tropical Atlantic and Africa begins to transition into its summertime monsoon state."

3) An El Niño event is not expected this year: "Another climate factor known to significantly impact Atlantic hurricane activity is the El Niño-Southern Oscillation (ENSO.) The three phases of ENSO are El Niño, La Niña, and ENSO-Neutral. El Niño events tend to suppress Atlantic hurricane activity, while La Niña events tend to enhance it (Gray 1984). Currently, the 2010-11 La Niña episode is dissipating. Based on observations and ENSO forecast models, ENSO-Neutral conditions are likely during the 2011 Atlantic hurricane season."

4) NOAA is increasingly using output from ultra-long range runs of the computer forecast models we rely on to make day-to-day weather forecasts, for their seasonal hurricane forecasts: "The outlook also takes into account dynamical model predictions from the NOAA Climate Forecast System (CFS), the European Centre for Medium Range Weather Forecasting (ECMWF), the United Kingdom Meteorology (UKMET) office, and the EUROpean Seasonal to Inter-annual Prediction (EUROSIP) ensemble. These models are indicating a high likelihood of an above normal season."

How accurate are the NOAA seasonal hurricane forecasts?
A talk presented by NHC's Eric Blake at the 2010 29th Annual AMS Conference on Hurricanes and Tropical Meteorology studied the accuracy of NOAA's late May seasonal Atlantic hurricane forecasts, using the mid-point of the range given for the number of named storms, hurricanes, intense hurricanes, and ACE index. Over the past twelve years, a forecast made using climatology was in error, on average, by 3.6 named storms, 2.5 hurricanes, and 1.7 intense hurricanes. NOAA's May forecast was not significantly better than climatology for these quantities, with average errors of 3.5 named storms, 2.3 hurricanes, and 1.4 intense hurricanes. Only NOAA's May ACE forecast was significantly better than climatology, averaging 58 ACE units off, compared to the 74 for climatology. Using another way to measure skill, the Mean Squared Error, May NOAA forecasts for named storms, hurricanes, and intense hurricanes had a skill of between 5% and 21% over a climatology forecast (Figure 2). Not surprisingly, NOAA's August forecasts were much better than the May forecasts, and did significantly better than a climatology forecast.


Figure 1. Mean absolute error for the May and August NOAA seasonal hurricane forecasts (1999 - 2009 for May, 1998 - 2009 for August), and for forecasts made using climatology from the past five years. A forecast made using climatology was in error, on average, by 3.6 named storms, 2.5 hurricanes, and 1.7 intense hurricanes. NOAA's May forecast was not significantly better than climatology for these quantities, with average errors of 3.5 named storms, 2.3 hurricanes, and 1.4 intense hurricanes. Only NOAA's May ACE forecast was significantly better than climatology, averaging 58 ACE units off, compared to the 74 for climatology. Image credit: Verification of 12 years of NOAA seasonal hurricane forecasts, National Hurricane Center.

How do NOAA's seasonal hurricane forecasts compare to CSU and TSR?
Two other major seasonal hurricane forecasts will be released over the next two weeks. On June 1, Phil Klotzbach and Bill Gray of Colorado State University (CSU) issue their forecast, and the British firm Tropical Storm Risk (TSR) will issue their outlook on May 24. A three-way comparison of the forecast accuracy of the three groups' forecast (Figure 2) reveals that all three organizations enjoy some success at making accurate seasonal forecasts, with NOAA and CSU making the best late May/early June forecasts overall. While the skill of these forecasts is low, they are useful for businesses such as the insurance industry.


Figure 2. Comparison of the percent improvement over climatology for May and August seasonal hurricane forecasts for the Atlantic from NOAA, CSU and TSR from 1999-2009 (May) and 1998-2009 (August). using the Mean Squared Error. Image credit: Verification of 12 years of NOAA seasonal hurricane forecasts, National Hurricane Center.

Jeff Masters

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Quoting Kahlest:
Been lurking here for a while, learning lots from you guys but don't really feel like I know enough to speak yet.


why? it hasn't stopped everyone else. lol
Member Since: August 11, 2008 Posts: 3 Comments: 1594
Quoting aquak9:
Great. Now I'm craving fried chicken.

I wonder if we will be able to see the rapture on radar. Or maybe the SPC will come out with some brimstone and hellfire maps.


'sposed to be accompanied by severe earthquakes
Member Since: August 13, 2007 Posts: 0 Comments: 10480
Quoting USAprimeCreditPeggy:
I bet pottery would eat them though.

Right now, I would eat just about anyone. er , I mean anything....
Member Since: October 24, 2005 Posts: 0 Comments: 24233
Great. Now I'm craving fried chicken.

I wonder if we will be able to see the rapture on radar. Or maybe the SPC will come out with some brimstone and hellfire maps.
Member Since: August 13, 2005 Posts: 165 Comments: 25838
Quoting Grothar:


I am so tired of these End of Times. I have been through so many of these through the centuries.


You don't have Miami here to post Satellite pictures of the Earth.
Member Since: July 6, 2010 Posts: 113 Comments: 31883
Hey, Greetings Grothar (and all you others too--)

It RAINING here all over the place.
Nice little Tropical Wave has brought us some dribbles all day long.
The sound of water falling into a cistern at 7:00pm is a lovely noise.
Member Since: October 24, 2005 Posts: 0 Comments: 24233
Quoting aquak9:


6pm EST? Will it go across the country like new years eve, or happen all at once? cause I could like get a really fast airplane, and get raptured over and over as I flew west.

Press- what kinda food does one serve at a rapture party?


Well ........................

Soul food, of course.
Member Since: August 22, 2008 Posts: 12 Comments: 6010
Quoting PityDAFool:
You all a bunch of suckers! you all be worrying about the end of times. End of times? FOOLS!

Hurricane season is just around the CORNER! It will be here faster than you can get fried chicken at a drive thru!

I pity the fools who ain't PREPARED!


ok then..........
Member Since: July 6, 2010 Posts: 113 Comments: 31883
Quoting DestinJeff:
0-0-0

It's an obviously solid forecast, what with the End of Times and all.


I am so tired of these End of Times. I have been through so many of these through the centuries.
Member Since: July 17, 2009 Posts: 71 Comments: 25996
Quoting aquak9:


6pm EST? Will it go across the country like new years eve, or happen all at once? cause I could like get a really fast airplane, and get raptured over and over as I flew west.

Press- what kinda food does one serve at a rapture party?


it will happen at 6 pm in each time zone...sort of a Rolling Rapture...seems to me the only appropriate food is left overs...
Member Since: August 13, 2007 Posts: 0 Comments: 10480
Quoting aquak9:


6pm EST? Will it go across the country like new years eve, or happen all at once? cause I could like get a really fast airplane, and get raptured over and over as I flew west.

Press- what kinda food does one serve at a rapture party?


Fast food, I would imagine. Good thing about it, you don't have to clean up afterwards.
Member Since: July 17, 2009 Posts: 71 Comments: 25996
Good evening guys.

Member Since: July 6, 2010 Posts: 113 Comments: 31883
Quoting Levi32:


Indeed. I'm surprised they only issued 9 ships.


Thought you would like it. They did some job, especially during World War II. A lot of people put a lot of effort over the years to get where we are. All we do is click a button and we have everything we need. They really worked at it.
Member Since: July 17, 2009 Posts: 71 Comments: 25996
Quoting presslord:


Saturday @ 6P...After Party @ my house...


6pm EST? Will it go across the country like new years eve, or happen all at once? cause I could like get a really fast airplane, and get raptured over and over as I flew west.

Press- what kinda food does one serve at a rapture party?
Member Since: August 13, 2005 Posts: 165 Comments: 25838
Quoting MrMixon:


Wow... talk about old school. Sheesh, why didn't you just use one of these? :)

The Weather Rock

Courtesy of GeoJono on Flickr


I wish I could roll on the floor and laugh, but I couldn't get up. That is funny.
Member Since: July 17, 2009 Posts: 71 Comments: 25996
Quoting PcolaDan:


Did Jane Austen join the blog too?


no, but that's an idea.

Naaaahhh...I could never be somebody else. Ya'll would recognize my style of writing immediately. I'd be busted like a blow-up tropical fish balloon.
Member Since: August 13, 2005 Posts: 165 Comments: 25838
Quoting presslord:


Saturday @ 6P...After Party @ my house...


I'll be there Press !!
Member Since: Posts: Comments:
Quoting Patrap:
yeah,yeah,,12-14,4-9,3-6,Blah,yak,blah.


Where and when and How Big?

When they get to dat point,,I'll give it some credence, till then it's all chest thumping to me.


Prepare today and be ahead of the call when it comes.

Food fer thought.


..We dont like Spam
well you see pat, they must conduct this chest thumping in order to reach your desired "where and when and how big"

lol

in all seriousness though, these predictions serve one goal, to protect the people. This is done in two different ways, the first being, it directly informs the public on how active the season will be, and the second being, it allows NWS to make better forecasts in the future.
Member Since: Posts: Comments:
Quoting aquak9:
nice to see some sense and sensibility return to the blog.

ok, about that rapture thingy- it's supposta happen, when?


Did Jane Austen join the blog too?
Member Since: August 22, 2008 Posts: 12 Comments: 6010
Quoting aquak9:
nice to see some sense and sensibility return to the blog.

ok, about that rapture thingy- it's supposta happen, when?


Saturday @ 6P...After Party @ my house...
Member Since: August 13, 2007 Posts: 0 Comments: 10480
nice to see some sense and sensibility return to the blog.

ok, about that rapture thingy- it's supposta happen, when?
Member Since: August 13, 2005 Posts: 165 Comments: 25838
Quoting Grothar:
Here is an article which some of you might find interesting. I know Levi would like it. Shows you what we had to put up with in the old days.


Link


Wow... talk about old school. Sheesh, why didn't you just use one of these? :)

The Weather Rock

Courtesy of GeoJono on Flickr
Member Since: March 26, 2006 Posts: 44 Comments: 1520
Quoting Grothar:
Here is an article which some of you might find interesting. I know Levi would like it. Shows you what we had to put up with in the old days.


Link


Indeed. I'm surprised they only issued 9 ships.
Member Since: Posts: Comments:
Member Since: August 13, 2007 Posts: 0 Comments: 10480
Here is an article which some of you might find interesting. I know Levi would like it. Shows you what we had to put up with in the old days.


Link
Member Since: July 17, 2009 Posts: 71 Comments: 25996
Quoting USAprimeCreditPeggy:
Ask Grothar if they did sst maps in 1950 BC.


Too late. I already posted it. I just had it lying around with some other papyrus notes.
Member Since: July 17, 2009 Posts: 71 Comments: 25996
Quoting USAprimeCreditPeggy:
Ask Grothar if they did sst maps in 1950 BC.

Yes. That's the same year NHC issued its first TWO:

Appropriate tropical weather-related image.
Member Since: November 8, 2009 Posts: 4 Comments: 13508
It looks like 98W is organizing at a good rate.

Link
Member Since: April 29, 2009 Posts: 75 Comments: 14214
Quoting HurricaneDevo:
did they do sst maps in 1950?


Yes.

Member Since: July 17, 2009 Posts: 71 Comments: 25996
Quoting Kahlest:
Been lurking here for a while, learning lots from you guys but don't really feel like I know enough to speak yet.


...that hasn't stopped the vast majority of us...
Member Since: August 13, 2007 Posts: 0 Comments: 10480

Miss. River at Baton Rouge




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Quoting VAbeachhurricanes:


yeah pottery wont take them :(
he would if you gave him more rum
Member Since: July 15, 2006 Posts: 170 Comments: 53530
Quoting aquak9:
the pets don't get to go- we covered that yesterday


yeah pottery wont take them :(
Member Since: Posts: Comments:
Our tropical wave is now over eastern Venezuela.

Member Since: Posts: Comments:
Quoting blsealevel:
I'm no Hydrologist, so I can't say if this article
I read from the Examiner is even valid enough to put any thought to it but it certenly is intreasting.

Link


Although generally-speaking it is a decent article, I can tell you from the perspective of a hydrologist who forecasts operationally for these areas there are some inaccuracies.
Member Since: Posts: Comments:
awww man...the blog's gone back charts and graphs and all that analytical discussion.

Going to dig in the dirt. See ya'll later. :)
Member Since: August 13, 2005 Posts: 165 Comments: 25838
Ah, but surely if you've been lurking long enough you know that ignorance never stops people from posting here! (I offer up myself as Exhibit A)

:)

I kid, of course.



Nope. Not kidding. :)
Member Since: August 13, 2005 Posts: 165 Comments: 25838
Quoting KEEPEROFTHEGATE:
so go ahead pet the polar bear good luck with that
you wouldnt need to pet the polar bear. as atmoaggie says,

Quoting atmoaggie:
Of course. When they are used to being around people and you have been around that particular animal enough to recognize moods, that is easy.

I don't think either of those apply well to polar bears in the wild.


you only need to be around it.

Surely it doesnt apply as well in the wild as it does with pets. But it applies nonetheless
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Member Since: July 15, 2006 Posts: 170 Comments: 53530

XX
Member Since: July 15, 2006 Posts: 170 Comments: 53530

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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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