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 hurrkat05:
i get your point teddy but i still say until the conditions change waves are going to have a rough time developing..the best chance will be the gom until the end of july...
LMAO! What do you think Ted is saying???
Member Since: September 2, 2009 Posts: 130 Comments: 21194
Quoting xcool:
14/9/4 MY NEW FORECAST .



make up your mine lol
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Quoting xcool:
14/9/4 MY NEW FORECAST .
Explain why.
Member Since: September 2, 2009 Posts: 130 Comments: 21194
560. xcool
14/9/4 MY NEW FORECAST .
Member Since: September 26, 2009 Posts: 2 Comments: 15684
Quoting will45:Is that written in Stone?


Maybe Stormtop will guarantee it since Stormkat is a friend.
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Quoting hurrkat05:
no will it's not written in stone just my opinion...and teddy the wave coming off the african coast will be gulped up by the shear and dry air..you going to see what im talking about in 48 hours..


That's the point I'm taking across with these waves. They are going to poof but while they are coming across from Africa before they poof, they tend to moisten up the environment a lot by each wave. Look what the wave off Africa has already done to the SAL.


Jul 10 12:00 UTC


Jul 12 12:00 UTC.

Look around the wave's environment, see the absence of dry air around the system? As this wave progresses westward it will continue to moisten the environment in front of it. Pretty dusty in the Caribbean though, models however are indicating increased moisture in the SW Caribbean, whether is a TD or not, so that could moisten up the E Caribbean.
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Quoting StormGoddess:

Mine did that too! Then for some reason it just fixed itself after I tried like a billion times. I wrote them a letter but by the time they wrote back they said that it seemed that I figured it out! I dunno. :(


Yeah. Mine works now after refreshing about twenty times. I went ahead and created a test blog just in case too. Hopefully it's fixed. Thanks to both StormGoddess and angiest for replying.
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Quoting xcool:



cmc ngp gfs Euro
With a nice ridge building in over Nicaragua in about 120 hours any development in the SW Caribbean would be pushed into the Yucatan, so I'm beginning to come into agreement with the Euro. I learned from futuremet a couple months ago that this ridge forming is due to the large amounts of disposable heat and relaxation of trades. I don't know if this is completely factual, but it does make sense.
Member Since: September 2, 2009 Posts: 130 Comments: 21194
1950
13 storms

Hurricane ABLE 12-22 AUG
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Quoting StormW:


And this one?



Yes.
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Quoting Squid28:


My sentiments exactly, I would be just as happy with a 0-0-0 season as opposed to a 12-6-2. I love watching ths storms form and come to life, but I also know on a very intimate basis what problems they cause (and would never wish so on my worst enemy). It is a real love hate type of situation, I hope I go the rest of my life without ever staring one down again.


Same thing is true of storm (tornado) chasers. The desire is for spectacular wedges off in a field away from homes and businesses, etc.
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Quoting TropicalAnalystwx13:

Looking nice.
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Quoting reedzone:
1998 is another great example.. First storm formed in late July..
How about 1950? 1950 consisted of 11 hurricanes and 8 majors (by the way 8 major hurricanes is the record), and that season started on August 12.
Member Since: September 2, 2009 Posts: 130 Comments: 21194
Quoting IKE:


I want to see what unfolds this season. Just hope me and my house live through it.


My sentiments exactly, I would be just as happy with a 0-0-0 season as opposed to a 12-6-2. I love watching ths storms form and come to life, but I also know on a very intimate basis what problems they cause (and would never wish so on my worst enemy). It is a real love hate type of situation, I hope I go the rest of my life without ever staring one down again.
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547. xcool



2 WAVE..
Member Since: September 26, 2009 Posts: 2 Comments: 15684
2002.. awesome example
14 storms

3 Hurricane ALBERTO 04-23 AUG
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Quoting hurrkat05:
no will it's not written in stone just my opinion...and teddy the wave coming off the african coast will be gulped up by the shear and dry air..you going to see what im talking about in 48 hours..


No Shear, No Dry Air.
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Quoting StormW:



You mean this?



Yes, that one.
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Quoting StormW:


Thanks Ted! Nice post. Gee, analysis data Hurrkat, what a novel idea!


Thanks Storm! I've been dying to stick it to stormtop for the past 5 years. Also, I should be ignoring StormTop but I'm not, I know that there are lurkers out there that join and look at one piece of data and say 'Yep, slow season' and I'm trying to get a point across to them that you have to read and interrupt data for you to make a much more accurate opinion. For all we know, you and I could be wrong and this season could be 12-14 named storms.. but I've never seen such unanimous agreement from all agencies that became bust.
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540. xcool



cmc ngp gfs Euro
Member Since: September 26, 2009 Posts: 2 Comments: 15684
Quoting reedzone:


We still have August through December to go through.. Look at past seasons that started late, lateness is not an indicator of a slow season.
Exactly. But those that skip to conclusions so rapidly end up being wrong 99% of the time. I just don't see why the season would be inactive with the factors present.
Member Since: September 2, 2009 Posts: 130 Comments: 21194
Quoting StormW:


What would you like to know about those diagrams?


I probably just need to squirrel away some time and read one with a definition of what the axes are as well as the acronyms (I am referring specifically to something posted some pages back that superficially resembles a hodograph.)
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1998 is another great example.. First storm formed in late July..
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Quoting Patrap:
Mother Nature takes a pause after Hole 3, Even par.

..She looks to be grasping for the Woods though, here on 4..


I hear Tiger Woods is good at plugging holes...

Maybe BP should hire him. Either way, hope the leak is plugged today.
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Quoting reedzone:


We still have August through December to go through.. Look at past seasons that started late, lateness is not an indicator of a slow season.


Again and I'm sure this will be ignored by most of the people predicting a slower season, the numbers in July don't matter at all. 1969 had 18 named storms, only 1 in July. 2007 had 15 named storms, 7 in September.
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Quoting reedzone:


We still have August through December to go through.. Look at past seasons that started late, lateness is not an indicator of a slow season.


Take 2004 as an example.
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509. hurrkat05 4:12 PM EDT on July 12, 2010

Is that written in Stone?
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Quoting clwstmchasr:


I picked 14-8-5 and I beginning to wonder if I'm too high. I thought we would have had 2 storms by now and 3 by the end of July.


We still have August through December to go through.. Look at past seasons that started late, lateness is not an indicator of a slow season.
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Quoting btwntx08:
btw dont quote hurrkat05 hes always wrong


Is she stormkat???
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Quoting hurrkat05:
cyber teddy i hate to disappoint you but you will not tack a storm for the rest of july. really hostile conditions have taken over the tropics..you won't see bonnie until early to mid august...


Please, call me Ted. ;-)
Let's begin shall we. Let's start off with current conditions. Shear shall we?











Remember, when looking at those images don't look at the current shear is as shear spikes and falls rapidly.. look at the trends since Mid-May when it really matters to the season. SAL? Also about average, we've had a dust storm off Africa so SAL's been blowing off into the Atlantic choking waves. However the amount of organized wave's we're seeing like the one emerging off the coast now is troubling. They tend to moisten up the environment for when a wave with model support emerges that's well organized has a decent chance at development. Basically they sacrifice themselves for the one's to come.
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"TOOT, TOOT..."
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Quoting jasoniscoolman2010x:
big wave on land wow



that what we said then they went poof
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Quoting Tazmanian:



are you JFV??


JFVcaster.
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Quoting earthlydragonfly:


Thanks Storm... MJO products is alot like trying to understand string theory for the Universe. Maybe a tad bit easier.. LOL


Yeah string theory may be a tad bit easier to understand.
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Quoting IKE:


I want to see what unfolds this season. Just hope me and my house live through it.


I do too!
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Quoting StormW:


An All-season Real-time Multivariate MJO Index

Latest 40 days,

Dynamical Model MJO Forecasts


Thanks Storm... MJO products is alot like trying to understand string theory for the Universe. Maybe a tad bit easier.. LOL
Member Since: July 1, 2005 Posts: 10 Comments: 1683
Quoting clwstmchasr:


I picked 14-8-5 and I beginning to wonder if I'm too high. I thought we would have had 2 storms by now and 3 by the end of July.
But were you expecting a neat major hurricane strength cyclone to develop in June? Come August, September, and October you'll be hoping for calm conditions like now. And many things can be attributed to the slow activity, one big one is the positive NAO that will be going negative in a few days.
Member Since: September 2, 2009 Posts: 130 Comments: 21194
516. IKE
Quoting hurrkat05:
ike im only going with 14 and that's generous...


I want to see what unfolds this season. Just hope me and my house live through it.
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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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