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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1514. BahaHurican
12:43 PM GMT on July 13, 2010
Quoting StormW:
Baha,
Here's a start:

Medium Range Forecasts for Africa
TYVM, TYVM.... this is quite useful indeed....
Member Since: October 25, 2005 Posts: 19 Comments: 22734
1513. nrtiwlnvragn
12:41 PM GMT on July 13, 2010
Taiwan Central Weather Bureau TC Tracker - Based on GFS Ensemble

The CWB TC Tracker is a monitoring system for objectively detecting tropical cyclone like vortices (TCLVs) in numerical model outputs. It is achieved by recognizing the mesoscale structures of tropical cyclones.


Click on image to view original size in a new window






The one in the South Atlantic is extratropical.
Member Since: September 23, 2005 Posts: 15 Comments: 11343
1512. BahaHurican
12:38 PM GMT on July 13, 2010
Quoting StormW:


Baha, what exactly are you looking for as far as African analysis maps?
Sorry for the delay. I'm looking for a basic surface analyisis chart, like the one OPC does for the unified surface....
Member Since: October 25, 2005 Posts: 19 Comments: 22734
1511. MahFL
12:38 PM GMT on July 13, 2010
Didn't Dr Masters say the African dust would be less this year due to plentifull African rain, seems like that part of his forcast is BUSTED.....as for Bastardi's 4 named storms in July.....
Member Since: June 9, 2004 Posts: 0 Comments: 3849
1510. mrsalagranny
12:35 PM GMT on July 13, 2010
Well off to work I go again.Cant wait till tomorrow I will have off 5 days.YAY!!!!!
Member Since: June 6, 2010 Posts: 0 Comments: 853
1509. mrsalagranny
12:33 PM GMT on July 13, 2010
July.Boy I cant even type this morning lol!!!!!
Member Since: June 6, 2010 Posts: 0 Comments: 853
1508. IKE
12:33 PM GMT on July 13, 2010
Quoting KEEPEROFTHEGATE:
morning storm ahh the first cup is teh best cup



Hmmm....nah.
Member Since: June 9, 2005 Posts: 23 Comments: 37860
1507. mrsalagranny
12:32 PM GMT on July 13, 2010
It looks like we are going through some quiet time right now.Come August-Sept. we are gonna wish we were back in uly again.
Member Since: June 6, 2010 Posts: 0 Comments: 853
1506. KEEPEROFTHEGATE (Mod)
12:30 PM GMT on July 13, 2010
Quoting WeatherNerdPR:
Good Morning. The tropics are STILL quiet, and our CV wave seems to have been destroyed by SAL.
its all good when there is nothing
Member Since: July 15, 2006 Posts: 178 Comments: 56140
1505. beell
12:30 PM GMT on July 13, 2010
Highlights from the 805AM Tropical Dust Discussion.

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 AM EDT TUE JUL 13 2010

...TROPICAL WAVES...

TROPICAL WAVE EXTENDS FROM 18N31W TO 6N29W MOVING W 15-20 KT.
...AN AREA OF DUST ASSOCIATED WITH A DRY SAHARAN AIR LAYER IS ACROSS MUCH OF THE
TROPICAL ATLC SUPPRESSING CONVECTION NEAR THE WAVE.

TROPICAL WAVE IS ALONG 51W/52W S OF 16N MOVING W 15-20 KT. WAVE IS SUPPRESSED
AND MASKED DUE TO A DRY SAHARAN AIR LAYER ACROSS THE TROPICAL ATLC KEEPING
CONVECTION TO A MINIMUM AND RESTRICTED
TO THE ITCZ.

TROPICAL WAVE IS ACROSS THE YUCATAN PENINSULA INTO THE E PACIFIC
EXTENDING FROM 19N88W TO 8N90W MOVING W NEAR 20 KT. THE WAVE ALSO
LIES AHEAD OF A DRY SAHARAN AIR LAYER AND A LARGE AREA OF DUST
ACROSS THE TROPICAL ATLC AND ACROSS THE CARIBBEAN.

...DISCUSSION...

GULF OF MEXICO...
A DRY AND STABLE AIRMASS LIES ACROSS MUCH OF THE GULF OF MEXICO
AROUND AN UPPER LEVEL RIDGE CENTERED OVER LOUISIANA...

CARIBBEAN SEA...
MOST OF THE MOISTURE ASSOCIATED WITH A TROPICAL WAVE...NOW OVER
THE YUCATAN PENINSULA...HAS MOVED OUT OF THE CARIBBEAN...SEVERAL STATIONS
CONTINUE TO REPORT THE PRESENCE OF DUST ALOFT.

ATLANTIC OCEAN...
...A DRY SAHARAN AIR LAYER ACCOMPANIED BY DUST COVERS MUCH OF THE
TROPICAL ATLC KEEPING CONDITIONS
FAIR.
Member Since: September 11, 2007 Posts: 145 Comments: 16922
1504. mrsalagranny
12:30 PM GMT on July 13, 2010
Good morning Storm and all my WU family.
Member Since: June 6, 2010 Posts: 0 Comments: 853
1503. WeatherNerdPR
12:29 PM GMT on July 13, 2010
Good Morning. The tropics are STILL quiet, and our CV wave seems to have been destroyed by SAL.
Member Since: July 7, 2010 Posts: 0 Comments: 5725
1501. MiamiHurricanes09
12:23 PM GMT on July 13, 2010
Quoting StormW:


You got that right!

Wonder how much empty space I'm gonna create today!
LOL!
Member Since: September 2, 2009 Posts: 130 Comments: 21194
Have a good day everyone!
Member Since: September 2, 2009 Posts: 130 Comments: 21194
1497. aquak9
Keeper- I like that. Maybe we could train it to eat oil?
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1496. KEEPEROFTHEGATE (Mod)
morning storm ahh the first cup is teh best cup
Member Since: July 15, 2006 Posts: 178 Comments: 56140
Quoting KEEPEROFTHEGATE:


i got me a new anti troll device taz claimed it as a avatar which is ok
He took it off.
Member Since: September 2, 2009 Posts: 130 Comments: 21194
Thank you. It does seem the real start of the season will be pushed further into the very hot months of Aug-Oct. Oh oh.
Member Since: June 16, 2005 Posts: 0 Comments: 1439
1493. KEEPEROFTHEGATE (Mod)
Quoting aquak9:
g'morning Keeper

tkeith, ok, I guess there will be plenty of on and off periods. Like it really matters anymore...


i got me a new anti troll device taz claimed it as a avatar which is ok
Member Since: July 15, 2006 Posts: 178 Comments: 56140
ECMWF 00z 240 hours. Note the A/B high.

Member Since: September 2, 2009 Posts: 130 Comments: 21194
1491. IKE
Quoting StormW:


Yeah, ECMWF shows the same at 168, however by 240, it weakens. Notice the bold isobar in the ATL. 1020mb...the next one in, at the very center, would be 1025mb.



True.
Member Since: June 9, 2005 Posts: 23 Comments: 37860
Quoting tkeith:
WW and Aqua, it's my understanding that with this new cap, that's bolted to to the top of the BOP, they can shut the oil off like a spicket, if the pressure remains high enough. If the pressure is too low they will have to attach a pipe to the new top and collect the oil from above. The higher pressures will mean the well is still intact down in the hole. I'm gaurdedly optimistic (fingers crossed)


Thanks and I hope that is the case so they can "shut it off" if they have to leave the site because of a storm.....
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1488. KEEPEROFTHEGATE (Mod)
looks to be another quiet day in atlantic so far so good
Member Since: July 15, 2006 Posts: 178 Comments: 56140
Quoting StormW:


Baha, what exactly are you looking for as far as African analysis maps?

FNMOC has the basics
https://www.fnmoc.navy.mil/wxmap_cgi/cgi-bin/wxmap_DOD_area.cgi?area=gfs_africa&set=Core
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1486. aquak9
g'morning Keeper

tkeith, ok, I guess there will be plenty of on and off periods. Like it really matters anymore...
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Quoting KEEPEROFTHEGATE:
good morning wunderground
Morning KOTG.
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1483. KEEPEROFTHEGATE (Mod)
good morning wunderground
Member Since: July 15, 2006 Posts: 178 Comments: 56140
1481. IKE
Quoting GTcooliebai:

Not necesserily, I do believe a Stronger A/B High forces stronger trades along with the Dry Saharan Air to reach the Caribbean Sea, limiting development.


Same here.

Here's the parallel GFS now...showing 1032 mb high...




In 162 hours....it's at 1031 mb's...

Member Since: June 9, 2005 Posts: 23 Comments: 37860
1480. tkeith
Quoting weathermanwannabe:


That makes sense given the nice presentation of the unit; that, unfortunately, is what it will look like for a week or more if they have to pull-off site due to a storm this Summer...
WW and Aqua, it's my understanding that with this new cap, that's bolted to to the top of the BOP, they can shut the oil off like a spicket, if the pressure remains high enough. If the pressure is too low they will have to attach a pipe to the new top and collect the oil from above. The higher pressures will mean the well is still intact down in the hole. I'm gaurdedly optimistic (fingers crossed)
Member Since: Posts: Comments:
Quoting rmbjoe1954:


This will allow the development of CV storms?

Not necesserily, I do believe a Stronger A/B High forces stronger trades along with the Dry Saharan Air to reach the Caribbean Sea, limiting development.
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1478. IKE
Quoting rmbjoe1954:


This will allow the development of CV storms?


More SAL.
Member Since: June 9, 2005 Posts: 23 Comments: 37860
Quoting StormW:


Thanks IKE!

The Accuweather Pro site has the ECMWF 240 hour run now, with lots of variables. The 1000/500 Thickness / MSLP indicates by day 8, it begins to weaken and fluctuates between 1024-1022mb, and at 240 hours the center of the ridge is 1024mb.

Quoting stormhank:
Maybe tropics will saty quiet thru July...Not going to say that about Aug. and Sept though

22-23 the ridge breaks down and the MDR gets going but at the same time Lows and troughs start working off the East coast again..so with luck what develops will re-curve early.
It is when that period ends sometimes the beginning of August that the islands, FL and GOM need to start panicking.
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Quoting stormhank:
internet explorer
That's your mistake. When using Internet Explorer you do not have spell check, the blog may appear stretched, and several tabs may be missing. I recommend you download the latest version of Firefox.

Sorry, had to do it...LOL.

Member Since: September 2, 2009 Posts: 130 Comments: 21194
Quoting IKE:


Nada? It shows a 1030 mb high building back in in day 7, 168 hours....Link


This will allow the development of CV storms?
Member Since: June 16, 2005 Posts: 0 Comments: 1439
Quoting mcluvincane:
lots of downcasting this morning I see. With the high pressures and SAL I can see why! So much for the very active hurricane season. Not going to happen folks. Above average maybe but not by much. Done watching the tropics for couple of weeks.
Watch. Now u said that, we're going to have 3 NS in July....
Member Since: October 25, 2005 Posts: 19 Comments: 22734
Quoting severstorm:
Morning all, They have the cap on. For some reason they pulled the pipe off the top of the cap.


That makes sense given the nice presentation of the unit; that, unfortunately, is what it will look like for a week or more if they have to pull-off site due to a storm this Summer...
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Quoting IKE:


Nada? It shows a 1030 mb high building back in in day 7, 168 hours....Link


sry...was looking for formation
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Morning storm. Do you know somewhere I can get a current surface analysis for N. Africa?
Member Since: October 25, 2005 Posts: 19 Comments: 22734
1468. aquak9
Quoting severstorm:
Morning all, They have the cap on. For some reason they pulled the pipe off the top of the cap.


no no no! that big round pipe is not part of the new cap. It's a new top part, all pretty and round, to attach the cap to. But it still spews.

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internet explorer
Member Since: September 8, 2005 Posts: 0 Comments: 1386
1466. aquak9
Quoting Neapolitan:


The new cap is in place; today BP will attempt to connect and test the apparatus that will, it is hoped, allow most/all of the belching crude to be collected.


neopolitan- you just proved my point w/that link. It's still spewing. Look at it. Yes, there's a new top, all straight and pretty, but there's no cap, no restriction of flow whatsoever.
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Morning all, They have the cap on. For some reason they pulled the pipe off the top of the cap.
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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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