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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yes BahaHurican and it is giving room for the other wave to develop that very one that is going to come off of the coast soon
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1763. KEEPEROFTHEGATE (Mod)
Quoting BahaHurican:
Do we get a new blog today, or tomorrow?
tomorrow doc says
Member Since: July 15, 2006 Posts: 175 Comments: 54858
1762. Patrap
#1760





Next post
I'll have an update Wednesday.

Jeff Masters
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Quoting wunderkidcayman:
GFS has it bad days and it's good days and today it one of the bad days


right... its a bad day because of what? it shows nothing forming?
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Do we get a new blog today, or tomorrow?
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GFS has it bad days and it's good days and today it one of the bad days
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Quoting wunderkidcayman:
you know guys I see that the SAL is really clearing out south of 20N

now



24 hours ago

Looks like that first wave is a SAL-wiper...
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Quoting IKE:
GFS operational and parallel...little to nothing through July 29th in the ATL. Parallel GFS has just about dropped Yucatan peninsula area development in 6-7 days.
May not get Bonnie til early August
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Quoting Patrap:


not for long
LOL go get'em, Pat...
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1755. KEEPEROFTHEGATE (Mod)
IslandsWeatherInc

why do that
Member Since: July 15, 2006 Posts: 175 Comments: 54858
Quoting KEEPEROFTHEGATE:
replaced with empty space and before i even finish lunch

We r getting better... bionic finger, almost...
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you know guys I see that the SAL is really clearing out south of 20N

now



24 hours ago

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1752. IKE
GFS operational and parallel...little to nothing through July 29th in the ATL. Parallel GFS has just about dropped Yucatan peninsula area development in 6-7 days.
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1751. Patrap
Quoting IslandsWeatherInc:

I'm your twin


not for long
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Quoting BahaHurican:
I [+]ed this. This would work real well for this blog too, if everybody would get serious about it. Like I keep saying "less talk, more action". DON'T tell us it's a troll - just [-], [!] and [Ignore].

TYVM
+
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1747. KEEPEROFTHEGATE (Mod)
replaced with empty space and before i even finish lunch

Member Since: July 15, 2006 Posts: 175 Comments: 54858
Quoting RidingTheStormOut:
Hi folks. Love the blog, been coming for a few years now. Love the info, love the friendship. Thanks all. I realize I am not a frequent poster, but, if I may. The JFV problem is quite a pain. The multiple handles, the having to wade through many posts to get to real info, the constant quoting of trolls and posts that have been deleted by the Admin. The way we handled a problem on a blog I frequent was this way. Anyone who came on multiple handles was denied. Anyone who quoted the offending persons quotes was banned for a day. If the offending person was quoted repeatedly by the same, he was what we called blackballed. By this I mean we had a tacit agreement to permanantly Iggy the person who kept quoting the offendeing person. It worked real well for the blog. I am sorry, this is probly not my place to say this, but quoting a troll is everything the troll wants. Thanks everyone for the wonderful info and times I do have on the Dr's great blog. Have a good day everyone.
I [+]ed this. This would work real well for this blog too, if everybody would get serious about it. Like I keep saying "less talk, more action". DON'T tell us it's a troll - just [-], [!] and [Ignore].

TYVM
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Quoting StormW:


Pretty much...just don't confuse more ridging with stronger ridging.


Thanks Storm. :) I've had people on other blogs tell me that's wrong. Wish I had thought to explain it that way. Instead of arguing for 10 hours. Lol.
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Quoting largeeyes:
I'm curious. Am I the only person who has went back and read some of the 2005 blogs? Amazing the small number of comments there. Some of it is really amazing to read. I loved how Dr. Masters declared the season over, only to have to talk about Zeta on Dec 30.
I guess we all go back now and again to view... u know, nostalgia... but the blog prolly had 1/10th the posting membership it has now. Wunderground grew a LOT after 2005...
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so how does the Cayman Islands the hurricane capital look for the season any ideas
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1742. KEEPEROFTHEGATE (Mod)
<
Member Since: July 15, 2006 Posts: 175 Comments: 54858
Quoting CaribbeanIslandStorm:
could I have the link to this satellite site? Thanks
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Quoting CaicosRetiredSailor:
Post unnecessary now...
R u still there? Can u say what wx was like yesterday in ur neck of the woods?
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Good Afternoon.

I know, I'm probably will disrupt, offend or irritate some. The reason that I don't post as much as I used to is all this babble about global climate without relating it to tropical weather. I actually don't mind some repeating observations, collected data, etc. but resent those here drawing conclusions from in my opinion insufficient data. Then on the other hand, I guess it's not any better than the guess-casting that is frequently thrown about on this blog with reference to tropical weather. Being educated in the sciences has made me less interested in some of the dialog here other for mere entertainment purposes.

'Not trying to sound elitest, on the contrary, drawing conclusions from insufficient data, and claiming it as fact, and then calling those who don't share their claims "deniers" or other derogatory names is elitest and unscientific.

I view this blog and occassionally post with questions and comments mainly to obtain advance warning on possible tropical development because I live and work in south Florida. I admit, I also read this blog for entertainment because some here have an excellent sense of humor.

I guess, I may consider this my first rant here but just am genuinely concerned science of late has become much too politicized, and I fear the consequences in some cases grave.
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1738. Patrap
2005 Hurricane legend and chart
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1737. angiest
Quoting angiest:


The Icelandic volcano has not actually been very bad, it is just in a bad position. More powerful volcanic eruptions have had negligible impact on climate (Mt. St. Helens), and significantly larger eruptions have had pretty major impact on climate (Pinatubo, Krakatoa, Tambora). IMHO, there won't be any major impact from Iceland (subject to change, of course).


According to one source cited in the Wikipedia article for the 2010 eruption of Eyjafjallajkull, the Volcanic Explosivity Index rating was a max of 4 (it may be lower that that, and it *is* an ongoing situation so the final verdict has certainly not been written). For historical perspective:

1980 Mt. St. Helens - VEI 5 (~10 times larger)
79 Vesuvius - VEI 5
1992 Pinatubo - VEI 6 (~100 times larger)
1883 Krakatoa - VEI 6
1815-1816 Tambora - VEI 7 (~1000 times larger)

In way of an extremely broad definition, the VEI basically describes the amount of magma and magma products a volcanic eruption can eject, factoring in the height of the eruption column. For this reason, "quiet" eruptions such as the eruption of Kilauea that started in the early 1980s and continues to this day has a low VEI number even though it has released a lot of lava and volcanic gasses in 30 years. The VEI is not very good for particular types of potentially devastating eruptions that are non-explosive.
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1736. Patrap
GOES-12 Atlantic Low Cloud product Image
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1735. Patrap
Quoting Baltimorebirds:
How do you go back to some of the old blogs?.Can you give me a link.


Just use the archive on the right side of this page.

That's why itsa there.


Previous Entries for 2010:

* July
* June
* May
* April
* March
* February
* January
* Complete Archive
* Complete Archive by Subject new!

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Quoting Baltimorebirds:
How do you go back to some of the old blogs?.Can you give me a link.


Two ways.

1) Complete archive link on the right hand side of this page

2) Change entrynum=1541 in the address bar to any lower number. If you enter 0 you get the very first blog.
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In the
Quoting Baltimorebirds:
How do you go back to some of the old blogs?.Can you give me a link.

In your browser address bar it should say something like http://www.wunderground.com/blog/JeffMasters/comment.html?entrynum=1541

Just change the number to see old blogs. I was in the 220-260 range reading some 2005 blogs. They were pretty funny, though most pictures no longer worked.
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Quoting StormW:


And that's Senior Chief.
LOL!! You beat me to it...
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Quoting CaribbeanIslandStorm:

How should Puerto Rico and the Virgin Islands fair out this season?


In my opinion, the Caribbean is not a good place to be at all this season.
Member Since: July 6, 2010 Posts: 113 Comments: 32528
If he chooses WAMI next I'll RDSL.
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Quoting StormW:
Back later.


C ya.
Member Since: July 6, 2010 Posts: 113 Comments: 32528
1727. Patrap
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Strong line of thunderstorms about to enter some big cities:
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Quoting TropicalAnalystwx13:


This is a 2004/2005 pattern. You tell us...

How should Puerto Rico and the Virgin Islands fair out this season?
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Hi folks. Love the blog, been coming for a few years now. Love the info, love the friendship. Thanks all. I realize I am not a frequent poster, but, if I may. The JFV problem is quite a pain. The multiple handles, the having to wade through many posts to get to real info, the constant quoting of trolls and posts that have been deleted by the Admin. The way we handled a problem on a blog I frequent was this way. Anyone who came on multiple handles was denied. Anyone who quoted the offending persons quotes was banned for a day. If the offending person was quoted repeatedly by the same, he was what we called blackballed. By this I mean we had a tacit agreement to permanantly Iggy the person who kept quoting the offendeing person. It worked real well for the blog. I am sorry, this is probly not my place to say this, but quoting a troll is everything the troll wants. Thanks everyone for the wonderful info and times I do have on the Dr's great blog. Have a good day everyone.
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Quoting CaribBoy:


SAL power

yeah, Those levels are suppose to go down, will see when that happens.
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Quoting weatherman12345:

how should south florida do this season


This is a 2004/2005 pattern. You tell us...
Member Since: July 6, 2010 Posts: 113 Comments: 32528
1718. SQUAWK
Quoting hurricane23:


FSU TC Return Period Calculator


Hey "killer," good to see you,
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Quoting CaribBoy:


SAL power


Which should not be a problem two weeks from now.
Member Since: July 6, 2010 Posts: 113 Comments: 32528
Quoting CaribbeanIslandStorm:

All these waves coming off of africa seem to be dyeing out!


SAL power
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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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