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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My Numbers 17 storms 9 hurricanes 6 majors and the crow is ready
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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.
None of the convection is associated to the wave according to the NHC 8:05 PM TWD:

TROPICAL WAVE IS ALONG 35W/36W S OF 18N MOVING W 15-20 KT. THERE
IS A MID LEVEL CYCLONIC ROTATION NW OF THE WAVE AXIS NEAR
17N38W. WAVE IS EMBEDDED WITHIN A WEAK MOISTURE MAXIMUM AS
INDICATED ON THE TOTAL PRECIPITABLE WATER IMAGERY. HOWEVER...THE
TROPICAL ATLC IS DOMINATED BY DRY SAHARAN AIR AND DUST N OF 10N.
THEREFORE THE SATELLITE SIGNATURE IS PARTIALLY MASKED AND THERE
IS NO ASSOCIATED SHOWERS/CONVECTION.

Member Since: September 2, 2009 Posts: 130 Comments: 21193
That model shows it coming to only my house-caster.
Member Since: September 10, 2007 Posts: 0 Comments: 11151
2159. viman
Good Evening! At this point in 2005 no one had really any idea the type of hyper-active season that lay ahead, maybe we expected an above average season but nothing like what really occured, you know what they say about hindsight...let's just buckle down, get prepared and see what mother nature dishes out this year. We have heard the predictions, we all have seen the numbers (SSTs, La Nina, SAL, MJO, etc) so lets see if all the data and computer models are as good as they say they are or does the tropics still have some tricks up the sleeve to show us.
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How about "borecaster" for the NHC right now. ;)
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The slow....cast.....ers....cast a little slower.
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I claim caster-caster, wishcasting for more wishcasters.
Member Since: July 8, 2005 Posts: 259 Comments: 24018
Blog Update!

July 13, 2010 - 7:20 PM EDT - Tropical Update - 7 Day Forecast
Member Since: September 2, 2009 Posts: 130 Comments: 21193
Quoting StormW:


I'll take a look. Oh yeah, Bustcaster


Has Spin-Caster or Wobble-Caster been taken yet? :)
Member Since: September 10, 2007 Posts: 0 Comments: 11151
2151. Ossqss
First time I checked out the forecast
SST's. Kinda like it is alive when you click and enlarge it an run it out some :)



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For those that are dying of inactivity, the EPAC may have a code red soon, although 96E has remained at 40% for a while because of disorganization:

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

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

1. AN ELONGATED TROUGH OF LOW PRESSURE LOCATED OFF THE SOUTHERN COAST
OF MEXICO IS PRODUCING A LARGE BUT DISORGANIZED AREA OF SHOWERS AND
THUNDERSTORMS. HOWEVER...THE SHOWER ACTIVITY HAS BECOME A LITTLE
MORE CONCENTRATED A COUPLE HUNDRED MILES SOUTHWEST OF ACAPULCO
DURING THE PAST FEW HOURS. 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 CANGIALOSI/STEWART
NNNN

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Quoting StormW:
Has slowcaster been used yet?

Only you , only you StormW could have thought of that one! Jokes asides, what are your thoughts on 11N/55W and 10N/37W, could be off a degree or 2 but you get the general area?
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Quoting StormW:
Has slowcaster been used yet?
Good evening Storm
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Quoting BahaHurican:
LoL still working my way up to it.... maybe tomorrow I will post something...
Ok, LOL.
Member Since: September 2, 2009 Posts: 130 Comments: 21193
Anyone around the North Carolina area, if so please let me know if you are. I have a question, that I need to ask, as I can not find any information on it in your local papers.
Member Since: November 15, 2005 Posts: 16 Comments: 4189
The Caribbean looks to be the upcoming hot spot for development as the TUTT begins to turn horizontally to the west and east, some weakening of the TUTT can be expected as well.

GFS 18z 60 hours.

Member Since: September 2, 2009 Posts: 130 Comments: 21193
Quoting MiamiHurricanes09:
Still waiting for your blog entry Baha...LOL.
LoL still working my way up to it.... maybe tomorrow I will post something...
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Quoting KarenRei:
Wind shear staying low:



All the way up to 40N, there's perhaps 5% of the map covered by 40 knot shear and ~10% by 30 knot. Tons of 5 and 10. All over these boiling waters... We sure are lucky that convection is being suppressed by the SAL. It'd look like a bad September out there if that wasn't around.


Look at that row of seven 5s.
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Quoting KarenRei:
Wind shear staying low:



All the way up to 40N, there's perhaps 5% of the map covered by 40 knot shear and ~10% by 30 knot. Tons of 5 and 10. All over these boiling waters... We sure are lucky that convection is being suppressed by the SAL. It'd look like a bad September out there if that wasn't around.


It wont be there in September.
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Quoting StormW:
Has slowcaster been used yet?
I wouldn't be surprised, LOL.
Member Since: September 2, 2009 Posts: 130 Comments: 21193
Quoting IKE:
GFS model has either forgotten what a tropical low is or July stays in shutdown mode through July 29th.


Sounds like 2004, another year affected by El Nino Modoki.
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2137. scott39
Is it me or was the pacific busy at the first part of the season, then it switched over to the Atlantic? Now its busy again. Waiting for the switch.
Member Since: June 13, 2009 Posts: 0 Comments: 6775
Quoting KarenRei:
Wind shear staying low:



All the way up to 40N, there's perhaps 5% of the map covered by 40 knot shear and ~10% by 30 knot. Tons of 5 and 10. All over these boiling waters... We sure are lucky that convection is being suppressed by the SAL. It'd look like a bad September out there if that wasn't around.
Conditions become unfavorable for development unless the system is accompanied by an anticyclone at 20 knots. Most of the Atlantic, central and eastern Caribbean, and the eastern Gulf of Mexico are all somewhat unfavorable. Relaxation of wind shear should slowly begin as the TUTT weakens.
Member Since: September 2, 2009 Posts: 130 Comments: 21193
2134. Patrap
Conson Floater - Rainbow Color Infrared Loop

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Quoting IKE:
What a surprise....

TROPICAL WEATHER OUTLOOK
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
800 PM EDT TUE JUL 13 2010

FOR THE NORTH ATLANTIC...CARIBBEAN SEA AND THE GULF OF MEXICO...

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

$$
FORECASTER CANGIALOSI

Almost forgot what a yellow circle looks like, lmao!!!
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Wind shear staying low:



All the way up to 40N, there's perhaps 5% of the map covered by 40 knot shear and ~10% by 30 knot. Tons of 5 and 10. All over these boiling waters... We sure are lucky that convection is being suppressed by the SAL. It'd look like a bad September out there if that wasn't around.
Member Since: Posts: Comments:
2131. IKE
What a surprise....

TROPICAL WEATHER OUTLOOK
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
800 PM EDT TUE JUL 13 2010

FOR THE NORTH ATLANTIC...CARIBBEAN SEA AND THE GULF OF MEXICO...

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

$$
FORECASTER CANGIALOSI
Member Since: June 9, 2005 Posts: 23 Comments: 37858
Quoting stormhank:
Great job bro I left u a comment...and for 2 days in a row no ugly comments that troll spray really does the trick lol
Thanks!
Member Since: September 2, 2009 Posts: 130 Comments: 21193
Quoting MiamiHurricanes09:
Blog Update!

July 13, 2010 - 7:20 PM EDT - Tropical Update - 7 Day Forecast
Great job bro I left u a comment...and for 2 days in a row no ugly comments that troll spray really does the trick lol
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2128. Patrap
96E rainbow

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2127. Patrap
ADDS Caribbean IR Loop
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Quoting BahaHurican:
Kept Katrina from forming until it got into waters just E of the Bahamas....
Still waiting for your blog entry Baha...LOL.
Member Since: September 2, 2009 Posts: 130 Comments: 21193
2125. IKE
GFS model has either forgotten what a tropical low is or July stays in shutdown mode through July 29th.
Member Since: June 9, 2005 Posts: 23 Comments: 37858
Quoting xcool:
normal season
Please stop saying that. If you had evidence of a normal season than I would support what you're saying, but if you're just saying "normal season" because the tropics are inactive right now, you're just asking to be wrong.
Member Since: September 2, 2009 Posts: 130 Comments: 21193
2123. Patrap
www.rap.ucar.edu
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2122. scott39
Is the wind shear going to be favorable for developement when the SAL clears out?
Member Since: June 13, 2009 Posts: 0 Comments: 6775
Quoting CybrTeddy:


Better not present him with facts, they'll ignore it anyways. I just want to have a good conversation on here before a troll, or a kid that doesn't have a life so he trolls a weather blog (stormtop and JFV), comes in and says ignorant statements like the one in question.

I understand CybrTeddy, after 3 years I still have a problem identifying so called "trolls" I guess I think everyone means well even if they are misinformed "one of my weaknesses I guess but we all have them " just want add I enjoy your contributions here as well.
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Quoting sailingallover:

But they are slowing down this season. Where is the wave that looked like it had so much potential 3 days ago. It is around the 10th one I have watched that has lost it's convection due to dust.
But things will change...
Kept Katrina from forming until it got into waters just E of the Bahamas....
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Ten year average 16/9/4. Interesting that the 2005 uber forecasts are coming back to the ten year average with this year's weak start. Statistics, they work, go figure...
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Quoting sailingallover:

But they are slowing down this season. Where is the wave that looked like it had so much potential 3 days ago. It is around the 10th one I have watched that has lost it's convection due to dust.
But things will change...


Just wait until the wave train kicks into high gear in August and September.
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2117. Ossqss
Click to enlarge



Click to enlarge and run to Monday

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Quoting StSimonsIslandGAGuy:
Dustcaster was one of the first caster terms being tossed around in July 2005 when some were saying that dust would hold back the 2005 season. The big dust outbreaks in July 2005 did not seem to slow down the season in any way whatsoever.

But they are slowing down this season. Where is the wave that looked like it had so much potential 3 days ago. It is around the 10th one I have watched that has lost it's convection due to dust.
But things will change...
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2115. Patrap


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About

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