More pre-season predictions of a very active Atlantic hurricane season

By: Dr. Jeff Masters , 3:02 PM GMT on July 12, 2010

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Hello again, it's Jeff Masters back again after a week away. Well, the past week was a wicked hot time to be in New England, where I was vacationing, and I certainly didn't expect to see 98° temperatures in Maine like I experienced! Fortunately, it's not hard to find cold water to plunge into in New England. Thankfully, the tropics were relatively quiet during my week away, and remain so today. There are no threat areas in the Atlantic to discuss at present, and none of the reliable computer models is forecasting tropical cyclone development over the next seven days. The NOGAPS model does show a strong tropical disturbance developing near the waters offshore of Nicaragua and Honduras this weekend, though. With not much to discuss in the present-day tropics, let's take a look at more pre-season predictions of the coming Atlantic hurricane season.

2010 Atlantic hurricane season forecast from Penn State
Dr. Michael Mann and graduate student Michael Kozar of Penn State University (PSU) issued their 2010 Atlantic hurricane season forecast on May 28. Their forecast utilizes a statistical model to predict storm counts, based on historical activity. Their model is predicting 19 to 28 named storms in the Atlantic, with a best estimate of 23 storms. The forecast assumes that record warm SSTs will continue in the Atlantic Main Development Region for hurricanes. Dr. Mann has issued two previous forecasts, in 2007 and 2009. The 2007 forecast was perfect--15 storms were predicted, and 15 storms occurred. The 2009 forecast called for 11.5 named storms, and 9 occurred (the 2009 forecast also contained the caveat that if a strong El Niño event occurred, only 9.5 named storms were expected; a strong El Niño did indeed occur.) So, the 2009 forecast also did well.


2010 Atlantic hurricane season forecast from the UK GloSea model
A major new player in the seasonal Atlantic hurricane season forecast game is here--the UK Met Office, which issued its first Atlantic hurricane season forecast in 2007. The UK Met Office is the United Kingdom's version of our National Weather Service. Their 2010 Atlantic hurricane season forecast calls for 20 named storms, with a 70% chance the number will range between 13 and 27. They predict an ACE index of 204, which is about double the average ACE index.

I have high hopes for the UK Met Office forecast, since it is based on a promising new method--running a dynamical computer model of the global atmosphere-ocean system. The CSU forecast from Phil Klotzbach is based on statistical patterns of hurricane activity observed from past years. These statistical techniques do not work very well when the atmosphere behaves in ways it has not behaved in the past. The UK Met Office forecast avoids this problem by using a global computer forecast model--the GloSea model (short for GLObal SEAsonal model). GloSea is based on the HadGEM3 model--one of the leading climate models used to formulate the influential UN Intergovernmental Panel on Climate Change (IPCC) report. GloSea subdivides the atmosphere into a 3-dimensional grid 0.86° in longitude, 0.56° in latitude (about 62 km), and up to 85 levels in the vertical. This atmospheric model is coupled to an ocean model of even higher resolution. The initial state of the atmosphere and ocean as of June 1, 2010 were fed into the model, and the mathematical equations governing the motions of the atmosphere and ocean were solved at each grid point every few minutes, progressing out in time until the end of November (yes, this takes a colossal amount of computer power!) It's well-known that slight errors in specifying the initial state of the atmosphere can cause large errors in the forecast. This "sensitivity to initial conditions" is taken into account by making many model runs, each with a slight variation in the starting conditions which reflect the uncertainty in the initial state. This generates an "ensemble" of forecasts and the final forecast is created by analyzing all the member forecasts of this ensemble. Forty-two ensemble members were generated for this year's UK Met Office forecast. The researchers counted how many tropical storms formed during the six months the model ran to arrive at their forecast of twenty named storms for the remainder of this hurricane season. Of course, the exact timing and location of these twenty storms are bound to differ from what the model predicts, since one cannot make accurate forecasts of this nature so far in advance.

The grid used by GloSea is fine enough to see hurricanes form, but is too coarse to properly handle important features of these storms. This lack of resolution results in the model not generating the right number of storms. This discrepancy is corrected by looking back at time for the years 1989-2002, and coming up with correction factors (i.e., "fudge" factors) that give a reasonable forecast.

The future of seasonal hurricane forecasts using global dynamical computer models is bright. Their first three forecasts have been good. Last year the Met Office forecast was for 6 named storms and an ACE index of 60. The actual number of storms was 9, and the ACE index was 53. Their 2008 forecast called for 15 named storms, and 15 were observed. Their 2007 forecast called for 10 named storms in July - November, and 13 formed. A group using the European Center for Medium Range Weather Forecasting (ECWMF) model is also experimenting with some promising techniques using that model. Models like the GloSea and ECMWF will only get better as increased computer power and better understanding of the atmosphere are incorporated, necessitating less use of "fudge" factors based on historical hurricane patterns. If human-caused climate change amplifies in coming decades, statistical seasonal hurricane forecasts like the CSU's may be limited in how much they can be improved, since the atmosphere may move into new patterns very unlike what we've seen in the past 100 years. It is my expectation that ten years from now, seasonal hurricane forecasts based on global computer models such as the UK Met Office's GloSea will regularly out-perform the statistical forecasts issued by CSU.

2010 Atlantic hurricane season forecast from Florida State University
Last year, another group using dynamical computer forecast models entered the seasonal hurricane prediction fray. A group at Florida State University led by Dr. Tim LaRow introduced a new model called COAPS, which is funded by a 5-year, $6.2 million grant from NOAA. This year, the COAPS model is calling for 17 named storms and 10 hurricanes. Last year's prediction by the COAPS model was for 8 named storms and 4 hurricanes, which was very close to the observed 9 named storms and 3 hurricanes.

Summary of 2010 Atlantic hurricane season forecasts
Here are the number of named storms, hurricanes, and intense hurricanes predicted by the various forecasters:

23 named storms: PSU statistical model
20 named storms: UKMET GloSea dynamical model
18.5 named storms, 11 hurricanes, 5 major hurricanes: NOAA hybrid statistical/dynamical model technique
18 named storms, 10 hurricanes, 5 intense hurricanes: CSU statistical model (Phil Klotzbach/Bill Gray)
17.7 named storms, 9.5 hurricanes, 4.4 intense hurricanes: Tropical Storm Risk (TSR), hybrid statistical/dynamical model technique
17 named storms, 10 hurricanes: FSU dynamical model
10 named storms, 6 hurricanes, 2 intense hurricanes: climatology

Only four hurricane seasons since 1851 have had as many as nineteen named storms, so 5 out of 6 of these pre-season forecasts are calling for a top-five busiest season in history. One thing is for sure, though--this year won't be able to compete with the Hurricane Season of 2005 for early season activity--that year already had five named storm by this point in the season, including two major hurricanes (Dennis and Emily.)

Tropical Storm Conson threatens the Philippines
Weather456 has an interesting post on why the Western Pacific typhoon season has been exceptionally inactive this year. It looks like we'll have out first typhoon of the Western Pacific season later today, since Tropical Storm Conson appears poised to undergo rapid intensification, and should strike the main Philippine island of Luzon as a Category 1 or 2 typhoon.

Next post
I'll have an update Wednesday.

Jeff Masters

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2413. Patrap
Conson Rainbow Image

Member Since: July 3, 2005 Posts: 414 Comments: 125476
Quoting TropicalAnalystwx13:


Central Africa:



Looks more like a Tidal wave in central africa..
Member Since: July 1, 2005 Posts: 10 Comments: 1681
Quoting StSimonsIslandGAGuy:
Is Texas and Mexico the fake GOM? Hmmmm.
He forgot about Mississippi too. Uh-oh...

There-are-only-2-states-around-the-GOM-caster.
Member Since: September 2, 2009 Posts: 130 Comments: 21032
Quoting fldude99:


I'm talkin about the real GOM..LA to FL

So Mexico and Texas don't exist to you???
They are a real part of the GOM also.
Member Since: Posts: Comments:
Quoting FLdewey:


Maybe for Christmas we'll all pitch in and buy you a globe.


One with the entire GOM circled in RED CRAYON!!
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Quoting earthlydragonfly:
(insert canned laughter along with a big Awwweeee boooooo)



That would more correctly be AAAWWWWWOOOOOOOOooooooooooooo! (It's all in the chin, you know.... ;-)

I am the zingcaster.
Member Since: Posts: Comments:
I am having trouble connecting to any websites in the Philippines.

Philippine Atmospheric, Geophysical and Astronomical Services Administration
The webpage "www.pagasa.dost.gov.ph" cannot be found
DNS error occurred. Server cannot be found. The link may be broken.

The Inquirer.net news website has not been updated since 12am last night.

But I am able to get through to some chat friends I have also some relatives too, but they are outside of Manila. I hope this isn't going to be a repeat of what happened last year.
TS Ketsana
Member Since: Posts: Comments:
2404. xcool
<< SLIDELL LA RIGTH BY MS
Member Since: September 26, 2009 Posts: 2 Comments: 15603
yea what about a

form-caster
will-caster
rip-caster
pressure-caster
direction-caster
Member Since: Posts: Comments:
Quoting cirrocumulus:
earthlydragonfly: Probably to the North.

The wave in front of Wal Mart has a mid-level cyclonic rotation: TROPICAL WAVE IS ALONG 35W/36W S OF 18N MOVING W 15-20 KT. THERE
IS A MID LEVEL CYCLONIC ROTATION NW OF THE WAVE AXIS NEAR
17N38W. WAVE IS EMBEDDED WITHIN A WEAK MOISTURE MAXIMUM AS
INDICATED ON THE TOTAL PRECIPITABLE WATER IMAGERY. HOWEVER...THE
TROPICAL ATLC IS DOMINATED BY DRY SAHARAN AIR AND DUST N OF 10N.
THEREFORE THE SATELLITE SIGNATURE IS PARTIALLY MASKED AND THERE
IS NO ASSOCIATED SHOWERS/CONVECTION.
OMG now that is freaking awesome... (in front of wal-mart by the quarter operated horse) LOL Unless you were here last night you have no chance of understanding this LOL
Member Since: July 1, 2005 Posts: 10 Comments: 1681
Quoting cyclonekid:
What wave?


Central Africa:

Member Since: July 6, 2010 Posts: 108 Comments: 30241
Quoting fldude99:


I'm talkin about the real GOM..LA to FL


The GOM is more than just LA-FL. I live in MS and even I realize this... LOL.
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Quoting ElConando:
ALL-BETS-ARE-OFF-CASTER.
*Thinks of JFV during Fay*

I-bet-my-life-it-isn't-going-into-the-GOM-caster.
Member Since: September 2, 2009 Posts: 130 Comments: 21032
Feel like I'm watching a game of Russian Roulette as these ginormous waves keep rolling off of Cape Verde. Sheesh. Glad I have several good books to read.

Goodnight!
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Quoting TexasHurricane:


huh? we already had Alex...


I'm talkin about the real GOM..LA to FL
Member Since: Posts: Comments:
ALL-BETS-ARE-OFF-CASTER.
Member Since: Posts: Comments:


Big Bad Bonnie?
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Quoting fire831rescue:
The-NHC-track-is-wrong-and-I'm-right-caster


The-NHC-is-wrong-and-this-is-not-a-TD-casters.
Member Since: July 8, 2005 Posts: 259 Comments: 23011
earthlydragonfly: Probably to the North.

The wave in front of Wal Mart has a mid-level cyclonic rotation: TROPICAL WAVE IS ALONG 35W/36W S OF 18N MOVING W 15-20 KT. THERE
IS A MID LEVEL CYCLONIC ROTATION NW OF THE WAVE AXIS NEAR
17N38W. WAVE IS EMBEDDED WITHIN A WEAK MOISTURE MAXIMUM AS
INDICATED ON THE TOTAL PRECIPITABLE WATER IMAGERY. HOWEVER...THE
TROPICAL ATLC IS DOMINATED BY DRY SAHARAN AIR AND DUST N OF 10N.
THEREFORE THE SATELLITE SIGNATURE IS PARTIALLY MASKED AND THERE
IS NO ASSOCIATED SHOWERS/CONVECTION.
Member Since: Posts: Comments:
I own a business and we take pictures of people on Roller Coasters and such in theme parks like Universal Studios..

I guess I would be a Coaster Caster...

(insert canned laughter along with a big Awwweeee boooooo)

Member Since: July 1, 2005 Posts: 10 Comments: 1681
The-NHC-track-is-wrong-and-I'm-right-caster
Member Since: Posts: Comments:
Don't-Believe-The-Models-Caster
Member Since: Posts: Comments:
How about this one?

Senior-chief-is-this-one-a-Florida-thretter?-caster.
Member Since: September 2, 2009 Posts: 130 Comments: 21032
Quoting TropicalAnalystwx13:
I believe Tropical Storm Bonnie will form from the Central African wave if something else doesn't. I still highly believe we will see Colin by August 1st.
What wave?
Member Since: Posts: Comments:
I'll be a swear-caster.... I swear I saw in jog a little. Or would that be a jog-caster...? Maybe even a wobble-caster...
Member Since: Posts: Comments:
Quoting earthlydragonfly:


Wabbit Seathon......


Duck season.......


Wabbit Seathon
Rabbit/Duck caster.
Member Since: September 2, 2009 Posts: 130 Comments: 21032
Quoting StormW:


Right it's a REGIONAL model. Since it senses something within it's bounds, and it's not trying to go global, not saying to go buy it, but it's something to put in the back of the mind when analyzing other models.

Uh oh...Global caster.
I see. ROFL, global caster.
Member Since: September 2, 2009 Posts: 130 Comments: 21032
Quoting StormW:


Taz, I thought it was duck season?


Wabbit Seathon......


Duck season.......


Wabbit Seathon
Member Since: July 1, 2005 Posts: 10 Comments: 1681
2379. xcool
StormW MAIL SIR
Member Since: September 26, 2009 Posts: 2 Comments: 15603
Member Since: Posts: Comments:
Quoting Tazmanian:
am a commet caster

Taz, you're one scarey somonb.
But I believe you have The Force with you.
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Quoting earthlydragonfly:


Is the center of the L to the north of most of the convection or just the way the upper atmosphere looks in the image?


Sorry... Im referring to the wave that is now sliding off the coast of africa
Member Since: July 1, 2005 Posts: 10 Comments: 1681
Quoting StormW:


Taz, I thought it was duck season?



lol
Member Since: May 21, 2006 Posts: 5089 Comments: 114041
2373. xcool
StormW OH THANKS .
Member Since: September 26, 2009 Posts: 2 Comments: 15603
Pinholeeye-caster
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Quoting StormW:


Just kidding around.

The NAM model, Yeah, I am the last one to look at it for cyclogenesis. And unless shear improves a lot, and something worked quick down the the surface, it most likely won't happen. However, it is rare and has it's moments. The only time I even slightly consider is like the Gulf. Ask yourself, what type of model is the NAM, and what area would the GOMEX be considered?


I love it! The Master Inquisitor!
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2370. Grothar
Joined the caster game a little late tonight, but did anyone mention the eye-casters. Last year or the year before (it's hard at my age to remember) Someone wrote, "I think that is an eye" and someone wrote back and said "That is not an eye, that is Jamaica" Anyone recall who that was?
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Quoting StormW:


Just kidding around.

The NAM model, Yeah, I am the last one to look at it for cyclogenesis. And unless shear improves a lot, and something worked quick down the the surface, it most likely won't happen. However, it is rare and has it's moments. The only time I even slightly consider is like the Gulf. Ask yourself, what type of model is the NAM, and what area would the GOMEX be considered?
LOL! The GOMEX is around the U.S in where the NAM specializes for forecasting.
Member Since: September 2, 2009 Posts: 130 Comments: 21032
Quoting cirrocumulus:


Is the center of the L to the north of most of the convection or just the way the upper atmosphere looks in the image?
Member Since: July 1, 2005 Posts: 10 Comments: 1681
2366. hcubed
Quoting K8eCane:
You all are Cyber Bullying JFV...you need to stop it


Yes. Do you hear that, JFV? Stop it.
Member Since: Posts: Comments:
am a commet caster
Member Since: May 21, 2006 Posts: 5089 Comments: 114041

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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.