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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Quoting gator23:

maybe not, but it definitely has better vorticity than some of our invests recently.


Your kidding right?
Member Since: July 6, 2010 Posts: 113 Comments: 32073
Quoting pottery:

Good Evening all.
About SAL and it's effects on surface temps. Water and Land.
I believe that the Jury is still not decided....
In theory, one would expect the 'shade' created by the dust to reduce temps.
But a layer of dust can also create a 'green-house' effect and prevent cooling/increase heating.
The latter is very noticeable here (Trinidad 11n 61w) where increased temps are noted with dust overhead.
So perhaps the dust will also create an environment over water to keep SST's high, or even to increase them.


I think it's both but I also think that the dust should act somewhat like a mirror and reflect more heat then can build up under it kind of like light colored shingles on a house roof. if that makes since.
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1262. gator23
Quoting TropicalAnalystwx13:


The Bahamas blob is nothing to worry about.

maybe not, but it definitely has better vorticity than some of our invests recently.
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Quoting gator23:
The Bahamas blob has some weak low lever Vorticity



The Bahamas blob is nothing to worry about.
Member Since: July 6, 2010 Posts: 113 Comments: 32073
Quoting cirrocumulus:
They built that WalMart supercenter ahead of schedule. It's supposed to be there later in July.


Not even SAL can compete with Wal-Mart..
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Excellent video, if anyone is watching the oil fix.

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1258. gator23
The Bahamas blob has some weak 500mb Vorticity



850mb

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1257. pottery
Quoting blsealevel:


Would the SAL keep ocean temp's down a few deg's sure appears that way right now to me anyway.

Good Evening all.
About SAL and it's effects on surface temps. Water and Land.
I believe that the Jury is still not decided....
In theory, one would expect the 'shade' created by the dust to reduce temps.
But a layer of dust can also create a 'green-house' effect and prevent cooling/increase heating.
The latter is very noticeable here (Trinidad 11n 61w) where increased temps are noted with dust overhead.
So perhaps the dust will also create an environment over water to keep SST's high, or even to increase them.
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They built that WalMart supercenter ahead of schedule. It's supposed to be there later in July.
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Quoting cirrocumulus:
They must be looking forward to rain in Dakar already. What a dry season they go through. These early waves are going to give them a wetter than normal July and contribute to moister conditions earlier and closer to the Sahara this year. Maybe the desert will retreat a little to the north.

You may be right!
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That must be a supercenter Wal Mart.
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Oops! Double post.
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They must be looking forward to rain in Dakar already. What a dry season they go through. These early waves are going to give them a wetter than normal July and contribute to moister conditions earlier and closer to the Sahara this year. Maybe the desert will retreat a little to the north.
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1251. gator23
Quoting GeoffreyWPB:
Where did you live during Andrew gator?


137 and Kendall Dr. Just north of Tamiami Airport
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Quoting Baltimorebirds:
What are you all seeing over africa that I don't see.


Here ya go Baltimorebirds.... It was a few hours ago and is gone now
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I would like to laugh at your comments Grothar…but I was born without smile muscles.
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Quoting gator23:




ST. OLAF?


I'm sorry, but that was awesome.
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Quoting MZV:


Looks like they're shifting the scale to have a max of 34C now. Things don't "look" quite as bad that way. Don't these sea temp maps usually top out at 32C?


I dont know enough about it to give a correct answer but it looks like 34C
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1245. JRRP
Quoting stormhank:
I know 1999 n 2004 were late starting but both turned out active

you meant 1998
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Where did you live during Andrew gator?
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1243. 7544
still watching the bahama blob at this hour getting a nice shapeto it just below so fla

well its better than reading 100 post abouy the jv dude lol
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Quoting Grothar:


You're right Geoff, shouldn't be talking about the Norwegian satellite station. But thought you might be interested since you posted the image from the St. Olaf obseratory.

The took the SST's off of the Southwest and Southeast coastal waters and they were near 90 deg. Unheard of this early. High temps all the way up to just South of Lake Worth, but nothing really happens up there anyway. Just take a look at the map on WU and you can see the temps.


But I need to know - will Lars Sturlerderken be a suitable replacement???
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1241. Grothar
Quoting gator23:

what video link.
I remember waking up the next day and my dad breaking out the battery operated TV and shouting to my mom OMG! They couldnt believe how flat everything was. It was scary as we were isolated where we lived since most all the trees were down. There was a camper on a house nearby no one knew where it came from.


If you look back in yesterdays blogs, there is about 2 hours worth of Hurricane Andrew videos. They were posting all day. Interesting videos. I was in Old Cutler at the time. (Not yesterday, during Andrew)
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1239. gator23
Quoting Grothar:


You're right Geoff, shouldn't be talking about the Norwegian satellite station. But thought you might be interested since you posted the image from the St. Olaf obseratory.

The took the SST's off of the Southwest and Southeast coastal waters and they were near 90 deg. Unheard of this early. High temps all the way up to just South of Lake Worth, but nothing really happens up there anyway. Just take a look at the map on WU and you can see the temps.




ST. OLAF?
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I know 1999 n 2004 were late starting but both turned out active
Member Since: September 8, 2005 Posts: 0 Comments: 1386
1237. Grothar
Quoting GeoffreyWPB:
Please stay on topic Grothar.


You're right Geoff, shouldn't be talking about the Norwegian satellite station. But thought you might be interested since you posted the image from the St. Olaf obseratory.

The took the SST's off of the Southwest and Southeast coastal waters and they were near 90 deg. Unheard of this early. High temps all the way up to just South of Lake Worth, but nothing really happens up there anyway. Just take a look at the map on WU and you can see the temps.
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1236. gator23
Quoting GeoffreyWPB:
Watched the Hurricane Andrew videos last night...brought back bad memories. We were barely affected up here in Lake Worth, but nerve-racking nonetheless.

what video link.
I remember waking up the next day and my dad breaking out the battery operated TV and shouting to my mom OMG! They couldnt believe how flat everything was. It was scary as we were isolated where we lived since most all the trees were down. There was a camper on a house nearby no one knew where it came from.
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1235. MZV
Quoting blsealevel:


Would the SAL keep ocean temp's down a few deg's sure appears that way right now to me anyway.


Looks like they're shifting the scale to have a max of 34C now. Things don't "look" quite as bad that way. Don't these sea temp maps usually top out at 32C?
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1234. viman
Good Night all... was just looking at this Paul the Octopus thingy with the World Cup and was thinking, maybe the NHC can hire him to do predictions for the upcoming season....hmmmm...then again maybe not.
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Sorry, wrong date.
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Quoting Baltimorebirds:
If memory serves me correct I think that happend back in 2006.Were their was a large area of sal over the atlantic that kept sst down.


Yep. But 2006 had very warm SSTs as well, despite this fact. Same with 2005.

Quoting blsealevel:


Thought so, that would make since with this.


It does so by preventing sunlight from reaching the ocean surface.
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Thought so, that would make since with this.
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Quoting GeoffreyWPB:
Watched the Hurricane Andrew videos last night...brought back bad memories. We were barely affected up here in Lake Worth, but nerve-racking nonetheless.


Agreed - nerve racking. One of my most vivid memories was sitting at my dining room table listening to the radio broadcasts - about midmorning the first day. They were talking about the zoo being flattened, no food for the animals, the airbase being destroyed. Remember wondering if we would have a business, anyway to support 4 kids, and if everyone we knew was alive. Very eery.
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Quoting zoomiami:
Baha - happy independence day! Nice you had a holiday.

Funny you've had all that rain - we haven't had that much, relatively speaking.

Do you know how much time JFV has to spend getting new emails, new names, etc? How can anyone spend that much time doing that stuff? And this has been going on for what, 3 years?
I'm kinda tired of all the chatter about him... on the rain, I'm really starting to feel paranoid about the persistent trough in this area.... possible hurricane alley once they start rolling????
Member Since: October 25, 2005 Posts: 19 Comments: 22140
Quoting blsealevel:


Would the SAL keep ocean temp's down a few deg's sure appears that way right now to me anyway.


Yeah, it does.
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Please stay on topic Grothar.
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Quoting stormhank:
anyone still think we'll see 15 plus storms this season ??? been a quiet July so far


Very easily. The current quiet period is wholly irrelevant.
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Watched the Hurricane Andrew videos last night...brought back bad memories. We were barely affected up here in Lake Worth, but nerve-racking nonetheless.
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1222. Grothar
Quoting GeoffreyWPB:
Those are from the St. Olaf Satellite Service.


Yes, Geoff, quite familiar with that station. It has been run by Dr. Geflerken for many years now. There is talk he may retire and Lars Sturlerderken may replace him. It has been quite a stir there, since the volcano and everything as you know.
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Oracle, I'm still waiting for the peril here... how long does it take to load????
Member Since: October 25, 2005 Posts: 19 Comments: 22140
Quoting Bordonaro:
A general statement to all my friends here on WU and the little trolls parading around.

We are all family, we respect one another here, we talk tropical weather during Hurricane Season.

Many folks add much here, we have real meteorologists, tropical weather specialists, meteorology students, several very astute young folk under 18. We have folks who love weather here and share and learn.

Those who want to disrespect my family will be reported and Admin will deal with you, as they see fit.

Thanks!


Nice post -- since we don't have blog police, it would be nice if people stopped thinking that they can come in and correct others.
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Member Since: July 6, 2010 Posts: 113 Comments: 32073


Would the SAL keep ocean temp's down a few deg's sure appears that way right now to me anyway.
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Quoting stormhank:
anyone still think we'll see 15 plus storms this season ??? been a quiet July so far
July's almost always quiet, especially this part. Things will pick up as we get closer to / into Aug....
Member Since: October 25, 2005 Posts: 19 Comments: 22140
Baha - happy independence day! Nice you had a holiday.

Funny you've had all that rain - we haven't had that much, relatively speaking.

Do you know how much time JFV has to spend getting new emails, new names, etc? How can anyone spend that much time doing that stuff? And this has been going on for what, 3 years?
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A general statement to all my friends here on WU and the little trolls parading around.

We are all family, we respect one another here, we talk tropical weather during Hurricane Season.

Many folks add much here, we have real meteorologists, tropical weather specialists, meteorology students, several very astute young folk under 18. We have folks who love weather here and share and learn.

Those who want to disrespect my family will be reported and Admin will deal with you, as they see fit.

Thanks!
Member Since: Posts: Comments:

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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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