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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2513. Patrap
.."Negative Ghostrider..the Pattern is Not Full"..
Member Since: July 3, 2005 Posts: 415 Comments: 125722
2512. help4u
Storm w what is the dgex model,it shows 2 storms hitting gulf coast from 126 hours to 162 hitting florida.
Member Since: Posts: Comments:
Quoting Drakoen:
What is that pattern?
Ooooooo, I like Drak trivia. I think you're speaking about the upper level pattern forecasted by the GFS in the eastern Atlantic. I'm probably wrong, but it's worth a try, lol.
Member Since: September 2, 2009 Posts: 130 Comments: 21032
Quoting MiamiHurricanes09:
Vomit commit caster. LOL, j/k. I really enjoy your images, please keep posting them.


Thanks a lot Miami..
Member Since: July 1, 2005 Posts: 10 Comments: 1681
Quoting Drakoen:
What is that pattern?


You tell me brother. I haven't been near a computer all day. I'm assuming The Cape Verde season will be rocking and rolling in the near future.
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Quoting Ivanhater:
Looks like it is about to heat up lol

Link

Interesting model, points one system approaching SC another approaching Bermuda!
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Quoting Drakoen:
Anyone noticing the pattern starting to take shape?



Unfortunately yes.
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Quoting StormW:


Looks like a string of pearls, doesn't it?
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2505. DirtDan
Quoting earthlydragonfly:


That shot was taken to the east looking at central florida. (orlando) from west orange county florida.



Fantastic Picture. I'm in Lake Mary so I know what the light shows can be like.
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Quoting fatlady99:


congrats, DragonFly. totally deserved, and couldn't happen to nicer coaster caster! :)


Thanks Fatlady
Member Since: July 1, 2005 Posts: 10 Comments: 1681
2503. Drakoen
What is that pattern?
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Quoting StormW:


Now that would be awesome! Oh, didn't notice your Davis until you mentioned it...I have a Vantage Pro2


I have to change the battery on the suite.. about every year or so I have to change it.. So now I only get readings while the sun is up because of the solar panel. lol
Member Since: July 1, 2005 Posts: 10 Comments: 1681
2500. xcool
Drakoen i do
Member Since: September 26, 2009 Posts: 2 Comments: 15603
Quoting earthlydragonfly:


Thank you Storm.. I did get invited to fly in a HHplane to try and capture lightning in the eye wall. Im not sure I could handle the vomit commit but I may just do it anyway. I need to build a special tripod so the cameras can handle the turbulence.
Vomit commit caster. LOL, j/k. I really enjoy your images, please keep posting them.
Member Since: September 2, 2009 Posts: 130 Comments: 21032
Quoting Baltimorebirds:
In my opinion I think that bonnie could show up around the 20th of july.I think thats when favorable conditions will finally come.

Baltimore Birds Bonnie Caster :o)!!
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Quoting StormW:


Great job!


Thank you Storm.. I did get invited to fly in a HHplane to try and capture lightning in the eye wall. Im not sure I could handle the vomit commit but I may just do it anyway. I need to build a special tripod so the cameras can handle the turbulence.
Member Since: July 1, 2005 Posts: 10 Comments: 1681
2493. Drakoen
Anyone noticing the pattern starting to take shape?

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2492. DirtDan
Serious low level vorticity on the wave that just came off the African Coast.
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Looks like it is about to heat up lol

Link
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2489. hcubed
Quoting fire831rescue:


Yes, it does.. But they are combined. They're called "Texaco" and are represented by a big red star with a T in the middle of it,


And don't forget: It's pronounced Teh-he-co.
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Quoting earthlydragonfly:


Thanks Taco.. I had Taco tonight as a matter of fact..

I figured they would have wanted this one since it has my Davis Weather Pro in the shot.. I waited sooooo many nights to get this shot. Not one of my best but I like it and makes since for wunderground.

You know I take a lot of Lightning pictures
and I have to say that was a Great shot....
It is hard to get just that right one and then
have it come out just right.... Now to have your weather pro in the back ground was really a nice shot....
WTG

Taco :o)
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2487. xcool
nice wave by Africa
Member Since: September 26, 2009 Posts: 2 Comments: 15603
earthlydragonfly, that's a nice little spark you took a picture of. Carpet and dry air?
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2455 Earth Dragon: Wow, Nice shot. That doesn't even look like a ground strike, unless it hit way far away deep into the ground cover.
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2484. SLU


Tropical waves being able to generate their own convection near the Cape Verde Islands is not something we normally see on July 13th. What this says is that the atmosphere has certainly become more unstable since the significant dry air/dust outbreak last week. That inconjunction with the warmer than normal SST and the deep layer easterly wind regime setting up across the deep tropics says to me that we are not very far away from the start of the Cape Verde season despite the computer models generally showing a lack of activity. With a pattern like this it's hard to see why they are so conservative. Which is why we should watch the wave near 40W of which the northern portion is on course to acquire more convection in a day or 2 as it moves away from the effects of the dry air and reaches warmer waters near 50W, then passing north of PR and ending up near the Bahamas this weekend. The southern portion is generating convection and vorticity in a conducive environment with low shear and then the wave coming off Africa which is very well defined.
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Quoting FLdewey:
Oops... I forgot the state shield:

ROFL!
Member Since: September 2, 2009 Posts: 130 Comments: 21032
Ban credit? Ah yes... "Care for a ban, sir?" Nah, just put it on my tab..."
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or heres one condition-caster
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Quoting StormW:


WOW!
Where did you take that one? That's gorgeous!


That shot was taken to the east looking at central florida. (orlando) from west orange county florida.
Member Since: July 1, 2005 Posts: 10 Comments: 1681
Good evening all. I just popped in for a minute and Wow. Who initiated a W-U Happy Hour without me??!

Bourbon is over by the ice bucket as usual, but geeeez I don't think any of you will need any more tonight.

Any word on the BP cap testing???

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2476. xcool
La Nina developing in the equatorial Pacific Ocean

We continue a steady decline of equatorial sea surface temperatures in the Pacific into a state that could be classified as a weak La Nina. The June monthly 3.4 anomaly fell just short of weak La Nina classification at -0.43, but the weekly reading has been at -0.5 or less since the week of June 2nd and the latest update showed a reading of -0.8. Therefore, it seems very likely that the month of July will see an average 3.4 anomaly in the weak La Nina range. Therefore, I would say we are in a weak La Nina at the moment.




The trade winds have been consistently indicative of a developing La Nina and we also maintain a cold pool beneath the sea surface which should be available to be upwelled over the next several months. The SST computer models continue to show a pluge into the moderate to strong La Nina range over the next few months, but are likely too fast with this development. I think we are probably going to be in a moderate La Nina by the Fall, but we will have to see if we bottom out in the fall and then head back up during the winter. This could have an effect on how the winter forecast will be laid out in the next few months.


Allan Huffman's
by
Member Since: September 26, 2009 Posts: 2 Comments: 15603
I guess "Alex" formed in the "other-crap" region of the body water formerly known as the Gulf of Mexico....
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2472. gator23
Quoting MiamiHurricanes09:
Hehehehe. Thanks.

spellcaster? or is that the Harry Potter blog.
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Quoting taco2me61:

Wow thats a nice Shot there DragonFly :o)


Thanks Taco.. I had Taco tonight as a matter of fact..

I figured they would have wanted this one since it has my Davis Weather Pro in the shot.. I waited sooooo many nights to get this shot. Not one of my best but I like it and makes since for wunderground.
Member Since: July 1, 2005 Posts: 10 Comments: 1681
Quoting earthlydragonfly:
I just re-read the email and it is this image..



Just beautiful, Dragonfly. You should be selling these as cards and prints... Great work!
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Quoting AussieStorm:

I would call them a wishcaster... wishing they were as good as a forecaster as you and StormW
Hehehehe. Thanks.
Member Since: September 2, 2009 Posts: 130 Comments: 21032
In other news, this is Hurricane Rita approaching "the other crap" region after just emerging off of the Gulf of Mexico.

Member Since: September 2, 2009 Posts: 130 Comments: 21032
Quoting earthlydragonfly:
Ill be honest... I didnt think everyone would get so into the Iwannabeacaster game.. Im glad most are having fun with it..

Oh by the way, Marketing from Wunderground sent me an email today asking me for permission to use one of my pictures in some of their media.. I haven't responded yet but thought it was pretty cool!! And I dont know what shot they want yet.


congrats, DragonFly. totally deserved, and couldn't happen to nicer coaster caster! :)
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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.