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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1314. Grothar
Quoting Grothar:


Cantinflas?? What is wrong with you Geoff. It is one of the greatest lines from "Treasure of the Sierra Madres" you must be slipping. LOL


His name was Alfonso Bedoya!
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Quoting Baltimorebirds:
I see you have a new avatar taz.



yup
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Never saw the flick Grothar.
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1311. Grothar
Quoting GeoffreyWPB:


I thought your avatar was Cantinflas!


Cantinflas?? What is wrong with you Geoff. It is one of the greatest lines from "Treasure of the Sierra Madres" you must be slipping. LOL
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1309. xcool


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1308. hydrus
Quoting GeoffreyWPB:
Today is the six-month “anniversary” of the Haiti earthquake. I remember being on the blog that night. No one thought it would be as bad as it was at the time.
I was posting too.Its kind of eerie looking back at that night now.
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Quoting CosmicEvents:
Oh no. I'm 100% sure that it's the character in my avatar who spoke that line in The Treasure of the Sierra Madre.


I thought your avatar was Cantinflas!
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1306. xcool


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1305. JRRP
i gotta go

los dejo con este impresionante video
Link
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Quoting Grothar:


I think the movie from which your avatar was taken, didn't mention badges, did it??? Great movie!
Oh no. I'm 100% sure that it's the character in my avatar who spoke that line in The Treasure of the Sierra Madre.
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Today is the six-month “anniversary” of the Haiti earthquake. I remember being on the blog that night. No one thought it would be as bad as it was at the time.
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Quoting CoffinWood:


mail, taz



got it
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1300. pottery
Quoting blsealevel:


sounds about right, I spent some time in west africa saw the dust storms, looked alot like a thick fog, lasted for days, the sunshine had to work hard to get through it though it was some kind of thick.

OK. Good point.
I have never seen the dust as thick as you have.
Throws a whole new light on the thing.
A dust-cloud that thick will certainly reduce sunlight penetration.
Interesting, thanks.
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1299. scott39
We are going to have a very busy Aug Sept Oct and Nov if were going to reach the high number of TCs forecasted. Also in my 30 years of tracking hurricanes its mostly going to happen in Aug and Sept. Then im reading that most will go west due to the high. If we have 10 hurricanes happen, in that short of a period time, look out!
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Quoting Grothar:


Keep posting my globes and see what else happens! LOL Sure you are pressing the correct tabs?
ROFL! I am. Oh well. Good night Gro!
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Quoting Tazmanian:
but am thinking about re moveing it be for the Admin sees it


mail, taz
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1296. Grothar
Quoting MiamiHurricanes09:
Ok...? What's going on with my handle that keeps posting the blog update post. Ughhh, been acting up all day.


Keep posting my globes and see what else happens! LOL Sure you are pressing the correct tabs?
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Good night everybody!
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1294. beell
What we could be looking at towards the end of next week if the wave that just left Africa and the one behind it survive the crossing. And that would include a close encounter with the TUTT or TUTT low for at least the first one. Looks like these waves will come in tilted from SW to NE. Hard to tell if one or both will fracture and go their separate ways (part of the wave towards the NW, part of it continuing on west.

Both charts valid next Monday at 18Z.

Photobucket
Link


Photobucket
Link

Based on the upper air chart for the same period, something developing in the Caribbean may occur first or at least have slightly better conditions in the broad pre-existing cyclonic flow over the western Caribbean.. Still, a very interesting pattern setting up.

g'nite.
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1293. JLPR2
Quoting MiamiHurricanes09:
That was my original forecast, and I have many factors to back me up.


Yep, 20 sounds about right, but I'm more of an 18 guy. XD
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but am thinking about re moveing it be for the Admin sees it
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1291. JLPR2
Quoting KEEPEROFTHEGATE:


anti-troll shark


That seems like an effective idea, lets feed sharkie >:3
LOL!

Hey everyone, decided to check the blog for a little while, I see everything is still quiet. :D
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Quoting pottery:

I understand what you are saying, but as I said there is no conclusive evidence (as far as I can find anyway), one way or the other.
Bear in mind that the SAL layer (dust) is by nature a very dry environment (dust cannot float about in damp conditions). So dry conditions would suggest clear, hot skies (except for the suspended dust of course).
I am not sure how much dust would be needed to reflect enough sunlight to make a difference, everything else being 'hot'. It would seem to me to require a LOT of thick dust to block enough sunlight to make a difference.


sounds about right, I spent some time in west africa saw the dust storms, looked alot like a thick fog, lasted for days, the sunshine had to work hard to get through it though it was some kind of thick.
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1289. Grothar
Quoting gator23:


see my vort maps below.


Yes, saw them and look up the other maps. Hope it is just a blob or a TUTT or a trough or as WinterAnalyst calls it a trof. LOL Just kidding Winter.
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Quoting Baltimorebirds:
The doc says 20 named storms more likley interesting indeed.But the total amount of storms could be higher?.Like 20 named storms but in all 24 depressions.I don't think we'll go that high.
That was my original forecast, and I have many factors to back me up.
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Quoting CoffinWood:


whoa, scary. is it shark week already?



lol yes no no one will mess with TAZ
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1286. KEEPEROFTHEGATE (Mod)
x
Member Since: July 15, 2006 Posts: 176 Comments: 55635
1284. pottery
Quoting scott39:
what will be the most active 30 days of this season? how mant TCs will form during this time?

I will have to consult my Calabash Tree.
But it's dark out there. There be serpents, jumbies....
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Quoting Tazmanian:
.


whoa, scary. is it shark week already?
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Ok...? What's going on with my handle that keeps posting the blog update post. Ughhh, been acting up all day.
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Quoting scott39:
what will be the most active 30 days of this season? how mant TCs will form during this time?


I'd say late august to mid september
Member Since: July 6, 2010 Posts: 113 Comments: 32706
1278. gator23
Quoting scott39:
what will be the most active 30 days of this season? how mant TCs will form during this time?

I am going to say September 1-September 30
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Quoting scott39:
what will be the most active 30 days of this season? how mant TCs will form during this time?
Late August through early September will likely be the peak. We could see multiple systems at once, but a number would just be inaccurate.
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1276. scott39
what will be the most active 30 days of this season? how mant TCs will form during this time?
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Quoting MiamiHurricanes09:
It's just upper divergence, no convergence. Basically, it should die out over night.



yeah...
Member Since: July 6, 2010 Posts: 113 Comments: 32706
1274. pottery
Quoting blsealevel:


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.

I understand what you are saying, but as I said there is no conclusive evidence (as far as I can find anyway), one way or the other.
Bear in mind that the SAL layer (dust) is by nature a very dry environment (dust cannot float about in damp conditions). So dry conditions would suggest clear, hot skies (except for the suspended dust of course).
I am not sure how much dust would be needed to reflect enough sunlight to make a difference, everything else being 'hot'. It would seem to me to require a LOT of thick dust to block enough sunlight to make a difference.
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Quoting TropicalAnalystwx13:


TUTT enhanced convection, along with a stalled trof.
It's just upper divergence, no convergence. Basically, it should die out over night.

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Quoting Grothar:


Remember Geoff, a smile is just a frown turned upside down, do just go stand on your head and you will be fine.

What are all these little blobs off of Florida?


TUTT enhanced convection, along with a stalled trof.
Member Since: July 6, 2010 Posts: 113 Comments: 32706
Quoting gator23:

nope. 91L's vort was a joke.
True, LOL.
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1269. gator23
Quoting Grothar:


Remember Geoff, a smile is just a frown turned upside down, do just go stand on your head and you will be fine.

What are all these little blobs off of Florida?


see my vort maps below.
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1268. Grothar
Quoting GeoffreyWPB:
I would like to laugh at your comments Grothar…but I was born without smile muscles.


Remember Geoff, a smile is just a frown turned upside down, do just go stand on your head and you will be fine.

What are all these little blobs off of Florida?
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1267. gator23
Quoting MiamiHurricanes09:
Looks anemic to me. Might just end up being a rain event for Cuba or Florida.

Oh absolutely I was just making an observation.
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1266. gator23
Quoting TropicalAnalystwx13:


Your kidding right?

nope. 91L's vort was a joke.
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Quoting gator23:

maybe not, but it definitely has better vorticity than some of our invests recently.
Looks anemic to me. Might just end up being a rain event for Cuba or Florida.
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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: 32706

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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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