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 StSimonsIslandGAGuy:


There were a lot more dust outbreaks earlier in the month, and Steve Gregory posted about them extensively. Unfortunately, his first 85+ blog entries have been removed.


SAL != dust

Dust may be associated with it, but the big suppression factor is that it's an inversion layer.

If you find the posts, let me know.
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I like the new avatar Patrap.
Member Since: September 2, 2009 Posts: 130 Comments: 21109
I am thinking the waves coming off africa will moisten up that area for the more potent waves that will follow end of this month into August
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2110. Patrap
Some entries are removed at the authors request.

Or by them manually.
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Blog Update!

July 13, 2010 - 7:20 PM EDT - Tropical Update - 7 Day Forecast
Member Since: September 2, 2009 Posts: 130 Comments: 21109
2107. scott39
Whoever says its going to be a slow season or bust, when its only July 13th 2010, is an idiotcaster!
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2106. Patrap
.."caught in a Bad Invest"..
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As Ive stated many times Im no expert but, heres my outlook for next 3 months..maybe 1 named by July 31st.. August..4 named September..5 named October...4 n a late season November storm...totals 16 as Im predicting and yess Ive got my crow recipe book on hand too lol
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2103. hydrus
Quoting AstroHurricane001:


Those numbers sound extremely reasonable.
Yes... I still believe it will be a very busy season..I am foolin around a bit since da blog is at a crawl.
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2102. Patrap
Conson

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Quoting stormpetrol:

The first hurricane in June in 15 years I think and we're off to slow start, I dare say no way! Just tell that to the Mexicans!


Better not present him with facts, they'll ignore it anyways. I just want to have a good conversation on here before a troll, or a kid that doesn't have a life so he trolls a weather blog (stormtop and JFV), comes in and says ignorant statements like the one in question.
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Quoting StSimonsIslandGAGuy:
Dustcaster was one of the first caster terms being tossed around in July 2005 when some were saying that dust would hold back the 2005 season. The big dust outbreaks in July 2005 did not seem to slow down the season in any way whatsoever.
Quoting StSimonsIslandGAGuy:
SAL was big in the tropical Atlantic in July 2005 and didn't stop an active July or tropical season afterwards. Steve Gregory was a guest blogger during 2005, and wrote extensively about the Saharan Dust.


Link

Link

There were more, he posted more than 90 entries in June-July 2005, but most are gone!


Those links are from near the end of July -- the 24th and the 31st, to be precise. No storms formed in the Atlantic between Gert on July 24th and Harvey August 3rd. And Gert was a weak BOC TS, ala TD2. If you ignore that one, you have to go back to Jul. 18th.
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2099. hydrus
Quoting Ameister12:

Just wait! It's still early in the season.
Just early in the season-caster.
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Quoting hydrus:
Catastrophe-Caster!!!...Or...Numerous-Stormcaster!!


Those numbers sound extremely reasonable.
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2096. hydrus
Quoting StSimonsIslandGAGuy:
Hmmmm I don't see the low ranked troll posts hydrus :P

Yeah I saw it :)
Low ranked troll posts...hhhhhhhhaaaaaaaa lol....Hmmmmmmm...Do not feed the L.R.T.P,s..
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St SImons guy...enjoyed your poem earlier bro lol..
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2093. xcool
normal season
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2092. EricSFL
Hi everyone!
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Quoting Patrap:
Saharan Air Layer Analysis 5-day Atlantic Movie


yeah, that.
Member Since: July 6, 2010 Posts: 113 Comments: 31883
Quoting thewindman:
SLLLOWWW SEASON!! So far running at or below average

Just wait! It's still early in the season.
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2089. Patrap
Saharan Air Layer Analysis 5-day Atlantic Movie
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Quoting robert88:
That wave will poof in no time. The SAL is still too close to the wave and it will suck all that dry stable air in. Need about another 2 weeks at the least to get that cleaned out.


You may want to check SAL maps again. There is no SAL near the African wave.
Member Since: July 6, 2010 Posts: 113 Comments: 31883
2086. beell
Quoting StSimonsIslandGAGuy:
Dustcaster was one of the first caster terms being tossed around in July 2005 when some were saying that dust would hold back the 2005 season. The big dust outbreaks in July 2005 did not seem to slow down the season in any way whatsoever.


Figured it had to have been used before...anyway, made me smile.
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Quoting thewindman:
SLLLOWWW SEASON!! So far running at or below average

The first hurricane in June in 15 years I think and we're off to slow start, I dare say no way! Just tell that to the Mexicans!
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That wave will poof in no time. The SAL is still too close to the wave and it will suck all that dry stable air in. Need about another 2 weeks at the least to get that cleaned out.
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Dust will go bye bye next week. lol.
Member Since: July 6, 2010 Posts: 113 Comments: 31883
Quoting StSimonsIslandGAGuy:


Let me join you Teddy. Sheesh.


Seems we have this every year, whatever a troll says the exact opposite happens. After Dolly everyone started killing off the season, same with after Chantal in 2007. 2009 the same people hyped it up into another 2005.
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Good evening!


My predictions:

Named storms: 17-20
Hurricanes: 8-11
Major Hurricanes: 3-6
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2074. beell 11:00 PM GMT on July 13, 2010
Another puff of dust coming out.
~ dustcaster
LMAO!!!
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2075. hydrus
Quoting StSimonsIslandGAGuy:
SAL was big in the tropical Atlantic in July 2005 and didn't stop an active July or tropical season afterwards. Steve Gregory was a guest blogger during 2005, and wrote extensively about the Saharan Dust.


Link

Link

There were more, he posted more than 90 entries in June-July 2005, but most are gone!
Did you read post# 2022 ?
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2074. beell
Another puff of dust coming out.
~ dustcaster

Photobucket

True Color modis composite
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2073. hydrus
Quoting thewindman:
SLLLOWWW SEASON!! So far running at or below average
Thats it,.... I have had it...If I see a cloud I am going to name it.
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SLLLOWWW SEASON!! So far running at or below average
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Quoting TropicalAnalystwx13:
24 hours ago:



Now:



Exactly what I posted a couple hours ago ;)
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2069. xcool


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2068. xcool
52W KEEP EYE OUT.
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2067. xcool
WAVE CLEAN SAL OUT YAYYY.
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24 hours ago:



Now:

Member Since: July 6, 2010 Posts: 113 Comments: 31883
2065. xcool



by wxman57
-Pro Met


by wxman57
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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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