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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If we couldn't laugh,
we would all go insane


BP North America
Moderator: Daren Beaudo
07-13-10/2:30 p.m. CT
Confirmation # 87627158
Page 3


"Now, as I said this test is not straight - we have got all of our scientists and we've got all the government scientists working together, paying attention to the way this is and they will collectively help make these decisions as we move along and of course, Admiral Allen is the national (innocent) commander of this."


http://www.bp.com/liveassets/bp_internet/globalbp/globalbp_uk_english/incident_response/STAGING/loc al_assets/downloads_pdfs/BPtranscript_tech_briefing07132010_330PMCST.pdf
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1964 was busy in atlantic as well,,kinda strange to have 2 basins with alot of activty,,as Ive been told normally one basin will be above average and the other below.. Joe bastardi has also said that tracks of storms lets say in west pac will coincide with atlantic tracks and vice versa
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Sorry forgot the Lon and Lat
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Quoting CybrTeddy:
Question: What was the most Hurricane/Typhoon/Cycone season ever? I know 2005 had the most named storms in the Atlantic, 1992 had the most for the Eastern Pacific.. but what was the record for the WPAC and the Indian Ocean, or the Southern Pacific?
1964 was the most active Western Pacific typhoon season, it consisted of 39 named storms, 26 typhoons, and 7 super typhoons.
Member Since: September 2, 2009 Posts: 130 Comments: 21091
Quoting CybrTeddy:
Question: What was the most Hurricane/Typhoon/Cycone season ever? I know 2005 had the most named storms in the Atlantic, 1992 had the most for the Eastern Pacific.. but what was the record for the WPAC and the Indian Ocean, or the Southern Pacific?
not sure teddy I know 1997 was a bad west pac season..with the strong El Nino that was occuring
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2208. xcool
READ MY POSTING
Member Since: September 26, 2009 Posts: 2 Comments: 15620
looks like a lot of convection to me on the water vapor!!!

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as of 18Z conson was right on top of manila..I bet they havin awful weather right now..hopefully no deaths or flooding will occur though
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Question: What was the most Hurricane/Typhoon/Cycone season ever? I know 2005 had the most named storms in the Atlantic, 1992 had the most for the Eastern Pacific.. but what was the record for the WPAC and the Indian Ocean, or the Southern Pacific?
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2204. stormy3
Given the mood in here, i'm going with bi-polarcaster
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At 11pm, this should be located offshore. :) Unless, the COC is seperated from the main convection



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Quoting StormW:


That would be based on the 18Z Surface Analysis map...that's 6 hours ago.
True. Forward speed from that time would put it around where you put it.
Member Since: September 2, 2009 Posts: 130 Comments: 21091
2201. xcool
Quiet Mid July - Enjoy it While it Lasts


After a rather active period covering the last week of June and the first week of July, the tropics have certainly quieted down this week. A significant factor responsible for the lack of activity in the past week is the current outbreak of dry, dusty Saharan air. The Azores-Bermuda High strengthened temporarily about a week ago, driving a large mass of dry air off the west coast of Africa. This dry air can be seen in the image below. The dry air is represented by the yellow and orange colors on the image


But it looks as though this dry air intrusion into the tropics will be short-lived. Computer model guidance indicates that the Azores-Bermuda High will continue to weaken and shift eastward over the coming week. This should reduce the amount of dry dusty air being driven off the west coast of Africa. In addition, several very large tropical waves with plenty of moisture are poised to slip off the west coast of Africa over next 3-5 days. Such bursts of dry Saharan air are not uncommon in June and July. It’s one reason why most seasons never really get started until the first week of August, as can be seen in the image below.





When looking at the frequency of Atlantic Basin tropical cyclones over the past 100 years, one can see that there is typically a sharp ramp-up in the number of storms right at the end of July into early August. Around that time, the last remnants of moderate wind shear and dry Saharan air depart the deep tropics, leaving a very favorable environment for tropical cyclone development. That’s what we’re expecting to happen in a few weeks. However, some models are suggesting that development could occur even sooner.

Over the past few days, several models have been indicating that something might flare up in the western Caribbean by late this coming weekend or early next week. Now it’s not uncommon for the models to predict such development on a regular basis during the hurricane season. Fortunately, the models are in error in predicting such development much of the time. But with the Saharan air thinning out by this weekend, and with a moderate tropical wave reaching the western Caribbean around that time, it’s an area that we’ll be keeping a close eye on.

As for the rest of the season, there is one thing that’s bothering me today. June and the first two weeks of July have been unseasonably warm across the northeastern U.S. This indicates that the high pressure we were expecting to remain over the central U.S. may be taking up residence a little farther to the east this summer. If such a pattern continues, then that may increase the risk of a major hurricane landfall farther west along the northern Gulf Coast - all the way to Texas. Previously, our outlook had indicated the highest risk from southeast Louisiana east through Florida. We may need to indicate a significantly increased risk of a landfalling hurricane farther west to Texas on our August update. Stay tuned…


BY Chris Hebert



KABOOM
Member Since: September 26, 2009 Posts: 2 Comments: 15620
2200. 900MB
Quoting earthlydragonfly:


I started a list yesterday regarding Wishcaster, stormcaster, fishcasters etc etc..


Anyone got dibs on Mojo-Caster?
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Since it seems we're most probably going to have a busy season Im gonna place my guess on the worst storm on the 2010 list....im goin with Igor..the name alone is scary lol
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Quoting xcool:
. MiamiHurricanes09 COME NOW.

KEEP EYE ON 40W
I will, I just don't understand why the NHC said it had no convection.
Member Since: September 2, 2009 Posts: 130 Comments: 21091
Quoting 900MB:
I have no idea what you guys are talking about, but count me in as a Mojo-caster!


I started a list yesterday regarding Wishcaster, stormcaster, fishcasters etc etc..
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Quoting viman:
Taz for blog-president...
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2192. viman
Taz for blog-president...
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EDFcaster
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2190. xcool
. MiamiHurricanes09 COME NOW.

KEEP EYE ON 40W
Member Since: September 26, 2009 Posts: 2 Comments: 15620
2189. 900MB
I have no idea what you guys are talking about, but count me in as a Mojo-caster!
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Quoting StormW:


I don't know...you can see the inverted "V" signature beginning near 42W, and the apex near 37/38W.

They put the axis around 35˚W. Oh well.
Member Since: September 2, 2009 Posts: 130 Comments: 21091
2187. viman
Taz-Caster.....
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0r poofCaster
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Master Disaster-Caster.
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Chicken littlecaster

BLaster caster

Drama caster----- Def. see JFVcaster
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Quoting IKE:
comment-caster


now oh would be a commet caster



heh heh heh



dont look at me am a good little boy
Member Since: May 21, 2006 Posts: 5091 Comments: 114719
The-cone-is-too-south-when-obviously-it-is-going-north-caster.
Member Since: September 2, 2009 Posts: 130 Comments: 21091
How about MegaCaster or DoomCaster?
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Quoting zoomiami:


nice avatar taz



thanks
Member Since: May 21, 2006 Posts: 5091 Comments: 114719
Quoting StormW:




I don't know, looks like convection to me.
Me too. They must be seeing something else we aren't.
Member Since: September 2, 2009 Posts: 130 Comments: 21091
2176. IKE
comment-caster
Member Since: June 9, 2005 Posts: 23 Comments: 37858
Quoting StormW:
Convection caster
once a storm forms it'll probably be "DOOM CASTER"
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Quoting Tazmanian:
YAY look at me go


i most have the most commets on WU now YAY


nice avatar taz
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2173. CJC111
Then there are the combinations such as slow dusty bustcaster
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Quoting StormW:


If anything, I'd give more credence to the one near 37W based on convection, and starting to show vorticity at the 850mb level. May have to watch it, as the 18Z shear forecast indicates upper level winds could become more conducive for development by the time it would reach the Caribbean.

Thanks, much appreciated, BBL later , enjoy the evening all.
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Quoting Tazmanian:
JFV caster


Got that one too
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joke caster
Member Since: May 21, 2006 Posts: 5091 Comments: 114719
JFV caster
Member Since: May 21, 2006 Posts: 5091 Comments: 114719
Quoting StormW:
Trofcaster


and of course The doctors official title is


Drum roll.......

MASTERCASTER
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YAY look at me go


i most have the most commets on WU now YAY
Member Since: May 21, 2006 Posts: 5091 Comments: 114719
Quoting GeoffreyWPB:


Has Spin-Caster or Wobble-Caster been taken yet? :)


yup we got wobble and spin...
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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.