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 gordydunnot:
Pottery I thought it might be a little to obvious but a first I didn't notice the long neck. Glad you pointed that out most unusual, don't know what I was looking at.

Yes, I know.
It's called 'selective vision' and it's pretty common.
It's the inability to see anything except what you are looking at.
Very strange.

heheheheh

See you guys tomorrow.
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Quoting Levi32:
Recent ASCAT didn't catch the whole thing. However, it's still clear that the surface circulation is not centered under the convection, but under the NW edge.


could probably put that down to shear.
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Quoting gordydunnot:
Pottery I thought it might be a little to obvious but a first I didn't notice the long neck. Glad you pointed that out most unusual, don't know what I was looking at.


I hope the photo isn't banned... due to that (Big) neck calling the bloggers attention.... :)
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Pottery I thought it might be a little to obvious but a first I didn't notice the long neck. Glad you pointed that out most unusual, don't know what I was looking at.
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SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE TIYAN GU
111 PM CHST FRI MAY 20 2011

PMZ161-171-201100-
KOROR PALAU-YAP-
111 PM CHST FRI MAY 20 2011

...A TROPICAL CYCLONE FORMATION ALERT HAS BEEN ISSUED FOR TROPICAL
DISTURBANCE 98W AS IT DRIFTS WESTWARD TOWARD FAIS...ULITHI AND YAP...

AT NOON CHST TROPICAL DISTURBANCE 98W WAS CENTERED NEAR 8.7 AND
141.3E. HEAVY THUNDERSTORMS ARE JUST SOUTH AND SOUTHEAST OF ULITHI
AND FAIS AND SOUTHEAST OF YAP. GUSTY WINDS TO 40 MPH AND ROUGH SEAS
OF 7 TO 9 FEET ARE LIKELY NEAR THESE THUNDERSTORMS.

AT 1200 PM CHST...TROPICAL DISTURBANCE 98W WAS NEAR LATITUDE 8.7
DEGREES NORTH AND LONGITUDE 141.3 DEGREES EAST. SUSTAINED WINDS
WERE IN THE 20 TO 25 MPH RANGE WITH GUSTS TO 40 MPH.

THIS IS APPROXIMATELY...90 MILES SOUTHEAST OF FAIS
140 MILES SOUTHEAST OF ULITHI
225 MILES EAST-SOUTHEAST OF YAP
AND 480 MILES EAST-NORTHEAST OF KOROR.


THUNDERSTORMS WILL BE SCATTERED IN COVERAGE AND WILL LIKELY GO
THROUGH DIURNAL WEAKENING AND STRENGTHENING PERIODS AS THEY MOVE
ACROSS THE YAP STATE AREA DURING THE NEXT FEW DAYS. MOVEMENT IS
TOWARD THE WEST-NORTHWEST AT 4 MPH.

RESIDENTS ARE ADVISED TO MONITOR WEATHER INFORMATION AVAILABLE FROM
THE YAP WEATHER SERVICE OFFICE...THE NATIONAL WEATHER SERVICE
FORECAST OFFICE ON GUAM...THE LOCAL DISASTER COORDINATION OFFICE AND
THE YAP STATE RADIO STATION. SMALL BOATS SHOULD EXERCISE EXTREME
CAUTION AND STAY IN PROTECTED WATERS OR IN PORT DURING THE NEXT FEW
DAYS. SMALL BOATS SHOULD NOT ATTEMPT INTER-ISLAND TRAVEL DURING THE
NEXT FEW DAYS.

THE NATIONAL WEATHER SERVICE WILL CONTINUE TO MONITOR THIS SYSTEM
AND UPDATE THIS STATEMENT AS NEEDED.

$$

SIMPSON/GUARD


Member Since: April 29, 2009 Posts: 75 Comments: 13280
Recent ASCAT didn't catch the whole thing. However, it's still clear that the surface circulation is not centered under the convection, but under the NW edge.

Member Since: November 24, 2005 Posts: 628 Comments: 26455
Quoting Levi32:
Decoupled:




Nice rain core.

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Decoupled:

Member Since: November 24, 2005 Posts: 628 Comments: 26455
Quoting gordydunnot:
I hear her grandfather was a Giraffe. Don't like to spread rumors. On a weather note, nice looking T/Wave south of Pottery may bring some preseason excitement to the blog. A lot of shear still but I notice over central America appears clouds on vapor loop are not being sheared. If this lack of shear moves a little further east watch out.

I was looking at that earlier too (the shear).
Also the western Caribbean sea is still showing some low pressures. Have been low for a couple weeks.
Will be fun to see what happens to this wave if it gets there.
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Link
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Big Low NW of Conus

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I hear her grandfather was a Giraffe. Don't like to spread rumors. On a weather note, nice looking T/Wave south of Pottery may bring some preseason excitement to the blog. A lot of shear still but I notice over central America appears clouds on vapor loop are not being sheared. If this lack of shear moves a little further east watch out.
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Quoting sunlinepr:


Thanks, Pottery, hope to meet with my sister (already there)




Glad I never had to buy her a necklace.
LOL, Good One!
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Quoting sunlinepr:


Thanks, Pottery

Yeah. Well if you like it!
I would leave the car behind, all things considered.
On the other hand, maybe you really LIKE sorethroats....
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Quoting pottery:

You going to end up with a really long neck...


Thanks, Pottery, hope to meet with my sister (already there)



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Quoting presslord:


precisely why they don't celebrate Christmas at Georgia Tech...they can't find three wise men...or a virgin...



I thought GT was one of the best schools in the country... haha
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Quoting gordydunnot:
Inside information from the UN rapture forecast center, update for the 2011 rapture rapture season. Prediction that only celibate monks and virgins will be raptured exact # is not certain but forecast is somewhere between 12 and 16 individuals. Will be updated after 5/21/2011.


precisely why they don't celebrate Christmas at Georgia Tech...they can't find three wise men...or a virgin...
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Quoting sunlinepr:
I really love my old pathfinder... Anyone knows if I can take it with me if I go in the (rup) rapture... Will a big chain from the bumper and around my neck do the trick??
Will I be able to control levitation of the SUV?

You going to end up with a really long neck...
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Quoting gordydunnot:
Inside information from the UN rapture forecast center, update for the 2011 rapture rapture season. Prediction that only celibate monks and virgins will be raptured exact # is not certain but forecast is somewhere between 12 and 16 individuals. Will be updated after 5/21/2011.

BAH!!
Foiled again.
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I really love my old pathfinder... Anyone knows if I can take it with me if I go in the (rup) rapture... Will a big chain from the bumper and around my neck do the trick??
Will I be able to control levitation of the SUV?
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Quoting spathy:


Thanks Pott.
I did to leave it out there for just a bit for dramatic effect.
But thank God it looks like the subject is turning back to WEATHER :O)

Had 1/4" in my guage when I got home from the mountains this afternoon.
Drizzled all day, all over the Island.
Put out a couple of bushfires too which was good.
The first T-Wave of the season just passing through..
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Inside information from the UN rapture forecast center, update for the 2011 rapture season. Prediction that only celibate monks and virgins will be raptured exact # is not certain but forecast is somewhere between 12 and 16 individuals. Will be updated after 5/21/2011.
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Quoting presslord:


we'll make that two big bottles of rum

One for me, and one for you.
Sounds good!
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For those who have not seen it, check Barefootontherocks blog.
Everything you ever needed to know about the flood control systems and whats going on in NOLA.

click 'blog index' at the bottom of this page to find it.
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Quoting Levi32:
Invest 98W is about to pull a TS Chris. The surface circulation is about to emerge naked in the NW quadrant:



It's a shame it looked so promising.
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Invest 98W is about to pull a TS Chris. The surface circulation is about to emerge naked in the NW quadrant:

Member Since: November 24, 2005 Posts: 628 Comments: 26455
Quoting pottery:

To Portlight. But make it 10.
:)


we'll make that two big bottles of rum
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Quoting pottery:

To Portlight. But make it 10.
:)

done and done. : )
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Quoting geepy86:
Where do I send a dollar?

To Portlight. But make it 10.
:)
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Quoting VAbeachhurricanes:


oh pottery you drove me into that one, and sorry press will there be any Coca-Cola present?

Sorry, I couldnt resist. :):))
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Where do I send a dollar?
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Quoting spathy:
What?
No comment?
What book did you think I was talking about?

http://books.google.com/books?id=4mcT7A371xQC& ;pri ntsec=frontcover&img=1&zoom=1&l=220




I hate to Mock such a serious subject.
Ya never know!
But some things are too good to resist!

Thanks for making that clear.
Zombie Protection is gonna be all the rage come Sunday.
Send $1:00 for a free copy of my last Thesis called "zombies I have known, and how I cooked them'.
Satisfaction promised. But no guarantee I'm afraid. Time has run out, you understand?
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A raining night!!!
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porn is so old school
weather is better
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Some seem to need a FB account in a bad way.

Member Since: July 3, 2005 Posts: 414 Comments: 125530
Quoting presslord:


my wife thinks I'm surfin' porn sites

This is far more fun.
And at the end of the day, you get to learn a few good things as well.
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Quoting presslord:


my wife thinks I'm surfin' porn sites


LOLOL,...Lowdy, then dont let her see the shower curtain...:O
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Quoting pottery:

Your'e very weird....
Have you spoken to anyone about this?

heheheheh


oh pottery you drove me into that one, and sorry press will there be any Coca-Cola present?
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Quoting presslord:


it would greatly help me preserve what little there is left of my reputation....if you would capitalize the word 'Coke'...

CokaCola, I think they meant.
Oh, and thanks for the Incentive.
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Quoting Thundercloud01221991:
 Why does this change with family radio?
Apparently, adherents to this prophecy believe that Matthew 24:36 was applicable only to the people of the time.
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Quoting EYEStoSEA:


I can relate to that exact feeling...lol...and my husband thinks the same thing.....and it is so much more than a weather blog, ya know, and without all the different personality types on here...it would be a real dud of a blog. You learn and laugh..all good :)


my wife thinks I'm surfin' porn sites
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Quoting VAbeachhurricanes:


will there be coke as well? nothing better than some rum&coke on the beach watching the world end.

Well said.
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Quoting VAbeachhurricanes:


will there be coke as well? nothing better than some rum&coke on the beach watching the world end.

I'll bring the Limbo bar, if someboddy brings the Ukeleles and the Hula Girls..
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Quoting kimoskee:
You guys are hilarious!!! I love it!!!

I always enjoy this time on the blog, pre-hurricane before the crazys come out.

My husband can't understand how I can be reading a weather blog and laughing so hard.

Keep it up!


I can relate to that exact feeling...lol...and my husband thinks the same thing.....and it is so much more than a weather blog, ya know, and without all the different personality types on here...it would be a real dud of a blog. You learn and laugh..all good :)
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Quoting VAbeachhurricanes:


will there be coke as well? nothing better than some rum&coke on the beach watching the world end.


it would greatly help me preserve what little there is left of my reputation....if you would capitalize the word 'Coke'...
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About JeffMasters

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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