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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2964. WAHA
Loop
Storm, do you think the wave in this loop near 10 N 45 W will have a good chance of being Bonnie?
Member Since: Posts: Comments:
Quoting StormW:


Skewcaster. LOL!

Morinin' sportguy.

Hi Storm, I was hoping to be called an August-caster :)
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2958. IKE
I would say those pre-season 2006 forecasts were a bust. From reading the 2006 predictions, is it really fair for someone to lower their seasonal #'s on October 3rd?
Member Since: June 9, 2005 Posts: 23 Comments: 37858
2956. WAHA
Quoting ShenValleyFlyFish:


You better. You sure wouldn't last long on a psychology site. lol

Duh!
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Quoting DestinJeff:
what is funny is that if 2005 is taken out of the discussion, then everyone would be referencing 2004's late start of an active season as the one to most parallel what is happening now.

2005 just really has skewed people's perception of normalcy.

nah July has skewed people's perception.
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2954. Skyepony (Mod)
Cops could face death in post-Katrina shootings
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2953. IKE
As for 2010 compared to 2005. Read this...

"Will the 2010 Season Be a Repeat of 2005?

* Weather experts are seeing some unsettling similarities between the 2010 hurricane season and the 2005 season, which produced 28 named storms, including Hurricane Katrina. For example, warm waters in the Atlantic Ocean are conducive to hurricane formation. This year set a record for the warmest water temperatures recorded in the tropical and eastern Atlantic. The May water temperatures were 0.09 degrees Fahrenheit above average, whereas in 2005 the temperatures were about 0.6 degrees Fahrenheit warmer than average. Vertical wind shear inhibits hurricane formation and growth. This spring, as in 2005, the wind shear is weaker than average. Moreover, el Nino has receded, as it did in 2005. While similar weather conditions is not an exact predictor of hurricane frequency and strength, the National Geographic reports that one forecaster sees the similar patterns as "ominous and foreboding." http://news.nationalgeographic.com/news/2010/06/100610-hurricanes-katrina-forecast-season-2010-scien ce-environment/14".......


From here. I've got this page bookmarked so I can come back and see how accurate they were when this season ends in 139 days.
Member Since: June 9, 2005 Posts: 23 Comments: 37858
Quoting DestinJeff:
This rarely gets any play, but this graphically depicts when seasonal activity is most likely to occur. You may not see this graphic again, so make sure and save it or something!


LOL, yea I've never seen that graphic before...

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2948. IKE
Quoting DestinJeff:
I seem to remember 2006 forecasted to be above-average as well. Anybody have those predictions?



Scroll down to pre-season forecasts....
Member Since: June 9, 2005 Posts: 23 Comments: 37858
Quoting WAHA:

First of all, it's impossible to be passive AND agressive at the same time.

Second, let's change the subject back to weather.


You better. You sure wouldn't last long on a psychology site. lol
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2943. MTWX
Quoting msgambler:
Morning Ike, hope your staying hydrated in this heat. Man it's been hot out here the last few days.

your telling me!!! we really need some rain up here in north miss!!
Member Since: July 20, 2009 Posts: 23 Comments: 1391
2940. SLU
Quoting weathermanwannabe:
2923. SLU 8:17 AM EDT on July 14, 2010

Well reasoned and said...With those "higher" trajectories, with some storms passing just to the North of Puerto Rico, South Florida is going to be subject to the "dreaded" approach through the Turks & Caicos, and over the Gulf Stream, on the way to the Peninsula....Its not going to be pretty this year come September.


I still can't find a reason to believe that it won't be a nasty season.
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2939. IKE
ATLANTIC OCEAN...
UPPER LEVEL RIDGING EXTENDING FROM THE GULF OF MEXICO COVERS
MUCH OF THE W ATLC. HOWEVER...A BROAD UPPER LEVEL LOW CONTINUES
TO SPIN N OF HISPANIOLA GENERATING SCATTERED
SHOWERS/THUNDERSTORMS FROM S OF 21N BETWEEN 65W-71W. A FEW
ISOLATED SHOWERS/THUNDERSTORMS ARE ALSO ACROSS THE WRN BAHAMAS
ASSOCIATED WITH INCREASED MOISTURE NEAR A SURFACE TROUGH
EXTENDING FROM S FLORIDA ACROSS CUBA. FARTHER E...RIDGING
DOMINATES THE ENTIRE BASIN ANCHORED BY A 1030 MB HIGH CENTERED
NEAR 40N43W. A DRY SAHARAN AIR LAYER ACCOMPANIED BY DUST COVERS
MUCH OF THE TROPICAL ATLC KEEPING CONDITIONS FAIR. ALOFT...AN
UPPER LEVEL TROUGH IS BETWEEN 38W-54W N OF 20N...WITH UPPER
RIDGING TO THE S OF 20N AND E OF 38W.
Member Since: June 9, 2005 Posts: 23 Comments: 37858
Quoting IKE:

Wish-caster!

I AM a wishing for some rain! A tropical system would be welcome (but Faye was a little overboard). After David, Frances and Jeanne, a hurricane is not welcome.
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2936. WAHA
Quoting StormW:


And, "What do you see on the ECMWF"

Good morning!
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Morning all.



We had a bit of rain this a.m. which held me up a bit....

And this is the latest African wave, from about 45 min ago...

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2932. WAHA
Quoting DestinJeff:


Passive-aggressive Downcaster Extraordinare!

First of all, it's impossible to be passive AND agressive at the same time.

Second, let's change the subject back to weather.
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2923. SLU 8:17 AM EDT on July 14, 2010

Well reasoned and said...With those "higher" trajectories, with some storms passing just to the North of Puerto Rico, South Florida is going to be subject to the "dreaded" approach through the Turks & Caicos, and over the Gulf Stream, on the way to the Peninsula....Its not going to be pretty this year come September.
Member Since: August 8, 2006 Posts: 0 Comments: 8255
Quoting IKE:


Looks like a blob of rain. I see what you're talking about.
It's a sharply inverted tropical wave that detached itself from the ITCZ and followed steering currents. Forecasted steering at that time takes the tropical wave through Florida and then consequently into the GOM. At the moment I'm not sure which tropical wave it is biting on but telling by the time-frame of the wave it it around 40˚W. By the time it is in the GOM it might be a little more than a tropical wave so I would watch it.

ECMWF 00z 144 hours - Tropical Wave over Florida.



ECMWF 00z 192 hours - Strong tropical wave over Louisiana.

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2926. WAHA
Quoting DestinJeff:


"Teh spelling gives it away. Just put him on Ignore."

Ei well nawt poot hem awn egnoar!
(I will not put him on ignore!)
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2924. WAHA
Quoting IKE:


Lmao.....I looked up teh meaning...

"Perfect and complete in every respect; having all necessary qualities"....

LOL.....:)

Very agreeable. I don't know how long I knew you, but you became poular fast. Best part, you're really nice.
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2923. SLU
-La nina
-Below average wind shear
-Well above average SSTs across the MDR
-Above normal moisture levels across the Atlantic
-Atlantic tripole
-Well established wave train
-Cold PDO
-The 1st storm of the season already being the 2nd most intense in Atlantic records in June
-Excessive heat build-ups
-Primarily negative NAO

Those, and a few more not mentioned, are the exact ingredients for a major hurricane season. I would not call the pre-season forecasts "hype" when basically all the agencies have predicted high numbers for this year and the other seasons we have witnessed with similar conditions have all been devastating ones.

Just look at the set-up of the High. Basically all the waves the models are showing, even the stronger ones, are all moving westwards into the Caribbean, near the Bahamas and Florida. If this pattern persists, when the storms do start to form, it could very well be a repeat of a 2004-like pattern which is another reason why we should not let our guard down and become complacent and impatient just because we think the season is a bust with the relatively slow start. Relative to 2005 at least, which will always be a bad example to follow from.

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2922. IKE
Quoting DestinJeff:


You have to admit, Ike, you are the consummate Downcaster.


Lmao.....I looked up teh meaning...

"Perfect and complete in every respect; having all necessary qualities"....

LOL.....:)
Member Since: June 9, 2005 Posts: 23 Comments: 37858
2921. WAHA
Quoting DestinJeff:
just though of another caster...

Feedbackcaster.

MEEEEEEEE! XD
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2919. WAHA
Quoting Jeff9641:
The wave in the center of the loop maybe something to watch the GFS and Euro are trying to latch on something and I wonder if its this wave.

http://www.ssd.noaa.gov/goes/east/catl/loop-vis.html

I think it will form into something, too. You're not alone. All it has to do is build more clouds and get closed.
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Quoting IKE:


Wish-caster!


New phrase picked up on this morning.....bundle-caster.


Most commonly used sayings in 2010 since the shutdown in the ATL started....

(1)SAL will decrease by.....
(2)Just wait til............
(3)The blog went dead!......
(4)Where is everyone?.......
(5)Just stick the downcaster on ignore.......
(6)Teh spelling is a giveaway...report him!.....


LOL!
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Quoting biff4ugo:
Thanks!
That explanes why conditions are so ripe for so long in the North Atlantic but only an A on the boards.


Just give it a few weeks and the ITCZ will start to feed and help "spin up" a few waves above the 10N mark (then coreolis takes over).
Member Since: August 8, 2006 Posts: 0 Comments: 8255
2914. IKE
Quoting DestinJeff:
Ike, did you see that ECMWF at 192? Is that a small system in the Gulf on there?


Looks like a blob of rain. I see what you're talking about.
Member Since: June 9, 2005 Posts: 23 Comments: 37858

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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.