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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Quoting sky1989:


2002 and 2004 both had 8 named storms in August. And 2007 had 8 named storms in September. I just have a feeling this year that we may not get the extremely high numbers but we may have some very strong and long-lived storms like 2003 and 2004.


That may very well be true; I was certainly expecting more from the early Carib season; guess it will all depend on the CV waves and the late Carib season

There was some discussion here in the last week or so about the fact that the expanse of warm SSTs maybe too extensive, causing a lack of focus for the heat energy, but to be honest, how many well organized waves have developed since the the season started? There hasn't been anything to really take advantage of the warm SSTs...
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Nice blow up N of Panama and Costa Rica, another rain event for Nicaragua/Honduras or a more Northward drift?
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Quoting sky1989:


2002 and 2004 both had 8 named storms in August. And 2007 had 8 named storms in September. I just have a feeling this year that we may not get the extremely high numbers but we may have some very strong and long-lived storms like 2003 and 2004.


This is how we're going to work out this season IMO.

June: 1 named storm, Hurricane Alex.
July: 1-2 named storms (probably off coast of Africa)
August: 5 named storms.
September: 7-8 named storms.
October: 2 named storms.
November: 1 named storm.
December: 1 named storm.

Total: 20 named at the most. 18 more likely.
Member Since: July 8, 2005 Posts: 259 Comments: 23012
Quoting Levi32:


Hey Baha, it's rough, I have to stay up late getting it done and then I wake up really late in the mornings, but it's gotta be done. I'm really thankful for this quiet period in the tropics so that I can catch up.




I don't think I could stand calculus in the summer! lol
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1 week verification of the GFS and GEFS suggests that they both did rather poorly by taking the MJO to octant 1 ahead of time.

1 week verification of the GFS and GEFS.
Member Since: September 2, 2009 Posts: 130 Comments: 21032
To user name Bordonaro,

Thank you for your response to my question earlier. Just curious what does Dr. Masters think about the chances of hurricane landfall in South and Western Florida this year?

Since La Nina is almost here what does this mean for hurricanes in Florida and what is the projected location of the Bermuda High? Thanks
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Quoting StSimonsIslandGAGuy:


At 100 comments a day you would be past 600,000 comments if you started then and kept it up :)



wow
Member Since: May 21, 2006 Posts: 5089 Comments: 114048
1905. sky1989
Quoting Drakoen:
Low Global ACE:



It is time for it to go back up.....
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1904. Levi32
Quoting BahaHurican:
Hey, Levi. How's the calculus coming along?


Hey Baha, it's rough, I have to stay up late getting it done and then I wake up really late in the mornings, but it's gotta be done. I'm really thankful for this quiet period in the tropics so that I can catch up.
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1903. sky1989
Quoting Floodman:


It's possible, even likely in some cases, but it's plausible to see 6 named in August, 9 in September and 3 more in October; what was the NHC forecast? 18-23?


2002 and 2004 both had 8 named storms in August. And 2007 had 8 named storms in September. I just have a feeling this year that we may not get the extremely high numbers but we may have some very strong and long-lived storms like 2003 and 2004.
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1902. scott39
Quoting StormW:


I'm not.
Hey Senior Chief, I didnt see your forecast of predicted TCs, will you post that again please?
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1901. Drakoen
Low Global ACE:

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1899. Drakoen
July 12: As if on cue, Typhoon Conson has developed in the Western Pacific July 12 but little activity is on the horizon elsewhere. After landfall of Conson in China in 3-4 days, the tropics are forecast again to be quiet through at least July 21. We'll see how the ECMWF forecast (10-days) performs.
PhD Ryan Maue
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Hey, Levi. How's the calculus coming along?
Member Since: October 25, 2005 Posts: 19 Comments: 20686
1897. angiest
Quoting StSimonsIslandGAGuy:


I said 'could have', not 'for sure' :) And she was intensifying steadily, although not explosively. Another 24 hours---Cat 5 would have been pushing it. Cat 4 would have been a distinct possibility.


That's certainly true, but even a strengthening storm can suddenly weaken rapidly. I'm thinking specifically of Hurricane Lili in 2002 which went from a solid cat 4 to a high-end cat in the hours before landfall.
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Quoting StSimonsIslandGAGuy:
If this blog had existed in 1992, a month from now, August 13 1992, a lot of people might have been saying the season was a bust.



i would have 100,000 commetes made by now or even more oh wait i was olny 5 at the time son nevere mine lol
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1895. scott39
Quoting IKE:


I would say yes, but only slightly on the top end...like the UKMET had 27...NOAA had 23. Maybe Dr. Gray lowers it by 1 when he issues his update Aug. 4th.

Then again we could have 2 or 3 the last 5 days of July and the numbers should stay the same.
If they dont lower it by much, were going to see a very busy, mostly Aug Sept,and some for Oct and Nov. Even it was lowered to 15-8-4!
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1892. Levi32
MJO will be coming into a position to cause mischief in the Atlantic during the next 2 weeks.

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Quoting Levi32:
Notice the upper easterlies becoming established over the eastern Atlantic south of 15N. This has been foretold by the GFS for a very long time now, and it is still establishing an easterly flow at 200mb across the entire basin south of 20N by July 25th. The TUTT will be far northeast of its current position by then, much more out of the way of developing systems. We could very well still see some activity before the month is out.



I've been watching that too. Definitely a very favorable pattern for Cape Verde development.
Member Since: September 2, 2009 Posts: 130 Comments: 21032
1889. IKE
Quoting scott39:
If nothing else developes in July, will forecasters adjust thier projections down?


I would say yes, but only slightly on the top end...like the UKMET had 27...NOAA had 23. Maybe Dr. Gray lowers it by 1 when he issues his update Aug. 4th.

Then again we could have 2 or 3 the last 5 days of July and the numbers should stay the same.
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Quoting scott39:
If nothing else developes in July, will forecasters adjust thier projections down?


It's possible, even likely in some cases, but it's plausible to see 6 named in August, 9 in September and 3 more in October; what was the NHC forecast? 18-23?
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1886. Levi32
Notice the upper easterlies becoming established over the eastern Atlantic south of 15N. This has been foretold by the GFS for a very long time now, and it is still establishing an easterly flow at 200mb across the entire basin south of 20N by July 25th. The TUTT will be far northeast of its current position by then, much more out of the way of developing systems. We could very well still see some activity before the month is out.



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1885. angiest
Quoting StSimonsIslandGAGuy:
I will note that the seasons of 1977, 1980, and 1992 all started late, but the 'A' storm was a Cat 5 in each case. Anita in 1977 and Andrew in 1992 made landfall at Cat 5, so a late start is not always good.

1983, Alicia was also a late start to the season. If Alicia had had another 24 hours, it could have reached Cat 4 or 5 as well.


I understand where you are coming from on Alicia, but she was small enough that an extra 24 hours could easily have been the death of the system too, depending on how close to shore, etc.
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Quoting AstroHurricane001:


Most of the GOM is warmer than average.



One small area of cool (relatively) temps in the area where TD2 made landfall...
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1883. scott39
If nothing else developes in July, will forecasters adjust thier projections down?
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1882. angiest
Quoting StSimonsIslandGAGuy:
If this blog had existed in 1992, a month from now, August 13 1992, a lot of people might have been saying the season was a bust.


Yeah, 1900 was quite a bust too. The first known storm didn't form until late August/early September.

1995 was a bit of a bust too. I mean, only 5 storms made landfall in the US and three of those were just tropical storms.

;)
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Quoting Floodman:


Well, any surface cooling due to Alex and TD2 will be reversed pretty quickly...if they haven't already


Most of the GOM is warmer than average.

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1879. IKE
Quoting StSimonsIslandGAGuy:
On this date in 2004, some people would have been saying it's a slow season. Two weeks later, even more might have been saying it.


Problem is...it's had comparisons to 2005 made by several sources(experts). People, including me, read that and think how busy it was and should be now based on that.

It's true that you cannot judge a season by June and July. I put that list on here yesterday that showed between 2000 and 2009 the average # of named storms between Aug. 1st and the end of the season is 12.8.

Odds are at least 13 more storms will form starting Aug.1st, 2010. Get ready! It only takes 1.

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Quoting StSimonsIslandGAGuy:
On this date in 2004, some people would have been saying it's a slow season. Two weeks later, even more might have been saying it.


I can see it now..

July 13, 2004

12Z ECMWF is out.. little if any TC activity shown through July 25th.. what a bust, this is not the season it was made out to be. Next year please!

2 months later and several places in Florida and Haiti are completely demolished.
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Quoting AstroHurricane001:
Wow, look how clear the Caribbean and GOM are, excepting that conspicious area east of Costa Rica. This is going to heat up that part of the basin rather rapidly. I wonder how long this will last.



Well, any surface cooling due to Alex and TD2 will be reversed pretty quickly...if they haven't already
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1875. beell
Quoting Drakoen:
TUTT axis draped across the caribbean and into the Atlantic. Unfavorable pattern for development.


Yup.
Prepare for a flurry of blob blog posts when the waves beging to interact with the TUTT.
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Quoting CycloneUK:
Conson is BACK



It's headed for Hong Kong. Will likely worsen the current flooding situation in South China. Floods and landslides there have already claimed over 470 lives. Link
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Meanwhile in the EPAC 96E is at a 40% chance:

ZCZC MIATWOEP ALL
TTAA00 KNHC DDHHMM
TROPICAL WEATHER OUTLOOK
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
1100 AM PDT TUE JUL 13 2010

FOR THE EASTERN NORTH PACIFIC...EAST OF 140 DEGREES WEST LONGITUDE..

1. SHOWERS AND THUNDERSTORMS ASSOCIATED WITH A LARGE AREA OF DISTURBED
WEATHER OFF THE SOUTHERN COAST OF MEXICO REMAIN DISORGANIZED.
ENVIRONMENTAL CONDITIONS APPEAR CONDUCIVE FOR DEVELOPMENT OF THIS
SYSTEM AS IT MOVES WEST-NORTHWESTWARD AT ABOUT 10 MPH. THERE IS A
MEDIUM CHANCE...40 PERCENT...OF THIS SYSTEM BECOMING A TROPICAL
CYCLONE DURING THE NEXT 48 HOURS.

ELSEWHERE...TROPICAL CYCLONE FORMATION IS NOT EXPECTED DURING THE
NEXT 48 HOURS.

$$
FORECASTER BROWN/ROBERTS
NNNN
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Wow, look how clear the Caribbean and GOM are, excepting that conspicious area east of Costa Rica. This is going to heat up that part of the basin rather rapidly. I wonder how long this will last.

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1869. IKE
The only thing I can figure is the MJO is heading away from this area in 1-2 weeks...if you believe this...Link. Looks like the high weakens on the end of the ECMWF run, so that shouldn't be a problem with it contributing to SAL.

Maybe it's still climatology, but that excuse is running out of time soon.

To me this seems like a normal season so far, but it's been built up so much it just seems awfully slow with no immediate threats in sight for at least 10 days...to maybe 2 weeks.
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1868. Drakoen
2010 season bust lol
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1867. Drakoen
TUTT axis draped across the caribbean and into the Atlantic. Unfavorable pattern for development.
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1866. sky1989
Quoting IKE:


I see a weak area of low pressure east of the islands at 144 hours. Maybe it's 1010 mb's or 1008mb's. Then it heads WNW...weakens and dies within 2 days.

Yeah...to answer your question...yes....little to nothing on that run...both of them.


Thanks Ike, it looks like conditions will only very slowly improve for cyclogenesis over the next 2 weeks. I figure once the NAO drops, allowing the Bermuda High to weaken and lowering dust levels, August could get interesting.
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Conson is BACK

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GFS shows a huge stacked closed 600 Decimeter HP sitting off the African coast in about 7 days. The SAL is going to get a little stronger. In about 10 days it shows the HP weaken and the E Atlantic being dominated by more of a LP in the upper atmosphere. The winds coming off Africa won't be as strong then. If that pans out then some of the waves might have a better chance of developing. I wouldn't expect a named storm for quite a while with all the dry stable air in the Atlantic. the only area for development will have to be a homegrown system or possibly in the Caribbean.
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About JeffMasters

Jeff co-founded the Weather Underground in 1995 while working on his Ph.D. He flew with the NOAA Hurricane Hunters from 1986-1990.