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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312. xcool
Baltimorebirds good forecast.
Member Since: September 26, 2009 Posts: 2 Comments: 15684
Quoting StormW:


I remember Bob asked when I thought we would see some development, and I think I had told him, 25 June, thereabouts.


Yeah, makes sense.. Unless this wave can overcome the dry air near Africa. Still holding on to an active season with 15-18 named storms.
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310. 7544
you have link xcool for joe b tia
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Roll the podcast.

In 3,2,1,..
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307. xcool
StormW yeah just go see video ;)@@@@
Member Since: September 26, 2009 Posts: 2 Comments: 15684
289. Unfortunatly it is easy to change ones IP address. Unless he has not been IP banned from the site before somehow I doubt it will have an effect.
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Just had to make a comment about out favorite troll.

Hope that admin is keeping a list of the email addresses he's used to avoid the ban.

All admin needs to do is find out what ISP he's going through, and write a letter stating that he's probably in violation of their terms of service.

Showing what addresses he used, and that the use of each one led to a ban could cause HIS ISP to drop him.

Using multiple email addresses for the express purpose to harass and annoy people IS a violation (at least with my ISP it is).

Anyone else been keeping a list?

Back to the tropics...
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303. xcool
i got ban for 48-hour Take It Like A Man
Member Since: September 26, 2009 Posts: 2 Comments: 15684
looks like the ITCZ is starting to moisten up... moving the moisture up over the 12N point



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Quoting Baltimorebirds:
I know el nino is dead.back in 2006 though not many forecasters saw that el nino was coming,and that it would have a efect on the season.


One forecast saw it coming, that is the UK MET forecast which called for about 13 storms for 2006. Now it's calling for 18-20 storms, I think they called for 10 storms last year, not sure though.
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298. xcool
StormW did you see joe b video ?
Member Since: September 26, 2009 Posts: 2 Comments: 15684
Quoting StormW:


The GEM is a Canadian Model


Afternoon StormW, nice and quiet out there in the open Atlantic for now, just as you predicted on the Bob Barometer show before Alex hit Mexico, I was listening ;)
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294. xcool
reedzone :0
Member Since: September 26, 2009 Posts: 2 Comments: 15684
Quoting xcool:
reedzone .My forecast 13 named storms haha lol


Still over 10 named storms, so it's definitely possible xcool ;)
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Good Afternoon...just popping in for some afternoon humor.
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Quoting JBirdFireMedic:


Host needs to institute an IP ban.
The IP ban any proxy he may get on.
You cant do an ip ban on just one person you have to understand how it works
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Quoting Baltimorebirds:
He changes email adresses.that's why.When you have the same e-mail adress you can't get another username.However when you change e-mail you can change your username.A lurker told me that and I want give out their name.


Host needs to institute an IP ban.
Then IP ban any proxy he may get on.
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Quoting IKE:


I had more rain in a heavy thunderstorm yesterday afternoon(5.23 inches), then Brownsville,TX. had in full, over TD2(3.63 inches).


Yep, but 2 hours north of Brownsville, we had over 10 inches of rain from Alex and TD2. There is still water standing in my backyard.
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283. 7544
so is it the africa wave the gem takes to so fla on gthe 22 or a dif. system?
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281. xcool
reedzone .My forecast 13 named storms haha lol
Member Since: September 26, 2009 Posts: 2 Comments: 15684
Quoting Baltimorebirds:
2005 has spoiled the minds of many.I remember on the first day of the 2006 hurricane season on msnbc,they were spread out all over the gulf talking about a potential very active season.But in the end when 2006 turned out to be a bust they never did that again.LoL.


It's not like El Nino is popping up again, this season is different. We will have more then 10 named storms this year, 100% confident on that. My forecast remains at 15-18 storms. Conditions are soo favorable in the months ahead, it's hard to say we will have less then 10 named systems lol.. People need to stop making assumptions after 2 months of Hurricane Season. Not blaming anyone currently on here, just for those who came in last night RIPing the season away.
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276. xcool
Member Since: September 26, 2009 Posts: 2 Comments: 15684
Quoting Neapolitan:
As someone else here wrote ealier, numbers can be used in different ways depending on a particular person's agenda. To attempt paint the catastrophe in the gulf as anything but that is disingenuous at best.


Agreed. I had to dig the chain email out of my TRASH. lol
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Afternoon, all.

Quoting hydrus:
The Caribbean thing is probably the remnant low of Karen.;0
LOL... u had to be there...

Quoting TampaSpin:


Na...nothing there to worry about......Shear is 30kts.....with no Vorticity really at all with mainly upper level Divergence caused by a trough that extends NNE of the blob. No worries.
Hey, TS... liked the little blue and yellow graphic u did earlier.... what I don't like about the "Bahama blob" is that it is yet another manifestation of yet another trough hanging out in the area... where there's been troughiness since the last week in June... almost 3 weeks? It's not this trough, but the persistence in the location right overhead that has me worried for T&C, The Bahamas, and EC FL....

Quoting Chicklit:
The latest Bahamian blob looks like a dandy.
Baha should be on here soon.
Sry took so long... lunch break. Teriyaki shrimp and scallops w/ vegetables... mmm mmm good...

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272. 7544
and now back to the tropics
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270. JLPR2
Quoting btwntx08:

no all i said "oh man hes back again ughh" and then he says that


well... nothing will change if we keep discussing it, so yeah... back to weather =)
Member Since: September 4, 2007 Posts: 7 Comments: 8733


Sure looks like the Wave that just left the coast of Africa has a lot of friends behind...
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265. 7544
does anyone know if this is the africa the gem shows over so fla on the 22 tia

Link
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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.