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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anyone have a link to the parallel GFS model site...Im using the GFS site from model analysis site that also has the NAM model??
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1663. IKE
Quoting Baltimorebirds:
That's interesting.Looks like it could impact the oil spill.


I would call that a spurious low.
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1661. Ossqss


http://www.drroyspencer.com/
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1660. IKE
Quoting BFG308:
Can we please not ban him today? After all, isn't it easier to just ignore him day after day if he only uses one handle?

And seriously dude, try typing with a different style/phrasing/spelling mistakes. It's way too easy. You're lucky if you get two comments in before someone calls you out!


Problem there is ....when one person quotes him it shows up on the blog for everyone to see.

There's no way to rid ourselves of him. It's like a bad zit that you just can't get the head to pop.

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1658. 7544
leave him he good he ask all the questions that others are a fraid to post . so let it be . lol
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1654. BFG308
Can we please not ban him today? After all, isn't it easier to just ignore him day after day if he only uses one handle?

And seriously dude, try typing with a different style/phrasing/spelling mistakes. It's way too easy. You're lucky if you get two comments in before someone calls you out!
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1653. NRAamy
hey StormW!

:)
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Quoting stormhank:
Im thinking perhaps a 1998 type season..bonnie didnt form that year til August 19th but season had like 10 hurricanes and after bonnie formed the season really picked up.. like 2004 when bonnie didnt form til early august also after which season really ramped up with activity but as Ive stated before Im no expert and I've been searching the net for "crow " recipes lol


There's still a chance for 3 or 4 storms by the end of July...I do think we will see 1 or 2.
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Or like 2010 when Bonnie formed in early August and...

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1646. 7544
Quoting Drakoen:


That's interesting


chek the gfs a system for fla like the nam shows the bahamas strom coming .what u think ?

Link
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Im thinking perhaps a 1998 type season..bonnie didnt form that year til August 19th but season had like 10 hurricanes and after bonnie formed the season really picked up.. like 2004 when bonnie didnt form til early august also after which season really ramped up with activity but as Ive stated before Im no expert and I've been searching the net for "crow " recipes lol
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1641. NRAamy
1629. SQUAWK 8:29 AM PDT on July 13, 2010
Well, I see that Janiel F Vargas (JFV) is back on with yet another aka.



Quoting WSVN:
Morning, Chief! Caught onto what?



SQUAWK!!!!!!!

:)
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1640. IKE
Quoting WSVN:
Storm, the ITCZ is finally north of 10 degrees north. A sign of things to come, perhaps? The CV is right around the corner, isn't it? Sadly, but so.


Need a hankie?
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1636. Drakoen
Quoting nrtiwlnvragn:
Not sayin I believe it, 12Z NAM 84 hours (system from the Bahamas).




That's interesting
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1633. IKE
Quoting nrtiwlnvragn:
Not sayin I believe it, 12Z NAM 84 hours (system from the Bahamas).




NAM showing one heck of a trough?

SYNOPSIS FOR THE GULF OF MEXICO
1030 AM CDT TUE JUL 13 2010

.SYNOPSIS...WEAK RIDGE FROM S FLORIDA TO 23N93W WILL SHIFT N TO
ALONG 28N WED THROUGH THU AND TO JUST N OF THE GULF FRI AND SAT
AS A TROUGH MOVES FROM E TO W ACROSS GULF THU THROUGH SAT.
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Quoting IKE:


Teh writing habit is a dead giveaway.

Teh ban feature is useless.


Ignore works well, but like the models it has to be refreshed every 6 hours.
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Not sayin I believe it, 12Z NAM 84 hours (system from the Bahamas).


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1629. SQUAWK
Well, I see that Janiel F Vargas (JFV) is back on with yet another aka.


Quoting WSVN:
Morning, Chief! Caught onto what?
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1628. IKE
Quoting WSVN:
Ouch, keeps, that was mean, how come? LOL, ^_^.


Teh writing habit is a dead giveaway.

Teh ban feature is useless.
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1627. xcool
yeah 7-11 day
Member Since: September 26, 2009 Posts: 2 Comments: 15684
Quoting StormW:


You caught on to that too, I see.


???
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Quoting xcool:
Bordonaro /000% models just cmc

Thanks, what are the othe computer models showing? Are they hinting at any development at all in the 7-10 day window?
Member Since: August 25, 2009 Posts: 20 Comments: 6785
1622. xcool
Bordonaro /000% models just cmc
Member Since: September 26, 2009 Posts: 2 Comments: 15684
1621. Squid28
Quoting StormW:


You caught on to that too, I see.


It's like a bad version of "Where is Waldo".....
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Quoting StormW:


Most likely the next 7-10 days.
thanks Storm W for your reply!! As far as numbers you expect wouldnt my outlook of 16 8 4 be fairly feasable???
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I hesitate to post this since I don't know the data range that was used to create it, however it does give a general idea of where storms form within the MJO octants. It is from CPC.

For example July:




Webpage for the other months
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Quoting btwntx08:

tell the cmc that lol

How many other computer models are in agreement with the CMC as of the last model run?
Member Since: August 25, 2009 Posts: 20 Comments: 6785

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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.