CSU and TSR continue to predict a near-average hurricane season

By: Dr. Jeff Masters , 3:18 PM GMT on August 04, 2009

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A tropical disturbance embedded in the Intertropical Convergence Zone (ITCZ), near 9N 35W, is moving west at about 15 mph. The heavy thunderstorm activity associated with this tropical wave has changed little over the past 24 hours, and remains disorganized. This morning's QuikSCAT pass showed a moderate wind shift, but nothing resembling an organized surface circulation. Top winds were in the 20 - 30 mph range. Strong easterly winds are creating about 20 knots of wind shear over the wave, which is marginally conducive for development. The disturbance is about 300 miles south of the Saharan Air Layer (SAL), so dust and dry air should not hinder development over the next few days.

Given the disturbance's current lack of organization, combined with the presence of 20 knots of wind shear, any development should be slow to occur. The forecast wind shear along the storm's path over the next five days is predicted to remain at or below 20 knots, which should allow some slow development. Sea surface temperatures (SSTs) will warm from about 28°C to 29°C as the storm progresses westward. The GFS model has been indicating some development is possible in several of its runs over the past few days, but has not been consistent with this prediction. None of the other models show any development of the system. NHC is giving the disturbance a low (less than 30% chance) of developing into a tropical depression over the next two days, which is a good forecast. The GFS and ECMWF models predict the system will be approaching the northern Lesser Antilles Islands by Sunday. Both models forecast the development of a band of very high wind shear just to the north of the islands at that time, so the long-range survival of anything that might manage to develop is in doubt.

CSU forecast team continues to predict an average hurricane season
A near-average Atlantic hurricane season is on tap for 2009, according to the seasonal hurricane forecast issued August 4 by Dr. Phil Klotzbach and Dr. Bill Gray of Colorado State University (CSU). The CSU team is calling for 10 named storms, 4 hurricanes, and 2 intense hurricanes, and an Accumulated Cyclone Energy (ACE) 83% of average. Between 1950 - 2000, the average season had 10 named storms, 6 hurricanes, and 2 intense hurricanes. But since 1995, the beginning of an active hurricane period in the Atlantic, we've averaged 15 named storms, 8 hurricanes, and 4 intense hurricanes per year. The new forecast is a step down from their June forecast, which called for 11 named storms, 5 hurricanes, and 2 intense hurricanes. Their April forecast called for 12 named storms, 6 hurricanes, and 2 intense hurricanes. The new forecast calls for a near-average chance of a major hurricane hitting the U.S., both along the East Coast (27% chance, 31% chance is average) and the Gulf Coast (26% chance, 30% chance is average). The Caribbean is also forecast to have an average risk of a major hurricane (37%; 42% is average).

The forecasters noted that while sea surface temperature anomalies have increased in the tropical Atlantic and surface pressures have fallen in recent weeks, which normally would favor higher hurricane activity, the presence of El Niño conditions in the Eastern Pacific should counteract these influences. They forecast that the current weak El Niño event will strengthen to a moderate event by September:

El Niño events tend to be associated with increased levels of vertical wind shear and decreased levels of Atlantic hurricane activity. Tropical Atlantic sea surface temperatures anomalies have warmed somewhat since our early June prediction and surface pressures have fallen somewhat. But, the negative influences of El Niño-induced strong Caribbean Basin and Main Development Region vertical wind shear typically dominate over surface pressure and sea surface temperature in the tropical Atlantic.



Figure 1. Change in Sea Surface Temperature anomaly (in °C) between July 2009 and May 2009. Most of the tropical Atlantic has warmed, relative to normal, over the past 2 months. Image credit: NOAA/ESRL.

Analogue years
The CSU team picked four previous years when atmospheric and oceanic conditions were similar to what we are seeing this year: weak to moderate El Niño conditions, and average tropical Atlantic and far northern Atlantic SSTs. Those four years were 2002, which featured Hurricane Lili that hit Louisiana as a Category 1 storm; 1965, which had Category 3 Betsy that hit New Orleans; 1963, which had Category 4 Hurricane Flora that devastated Cuba; and 1957, which didn't have any hurricanes that hit hit land during the peak part of hurricane season. The mean activity for these four years was 9 named storms, 4 hurricanes, and 2 intense hurricanes--almost the same as the 2009 CSU forecast.

How accurate are the August forecasts?
The August forecasts by the CSU team have historically offered a skill of 45 -62% higher than a "no-skill" forecast using climatology (Figure 2). However, they are using a new forecast scheme this year, so it is difficult to judge how skillful this year's forecast might be.


Figure 2. Accuracy of long-range forecasts of Atlantic hurricane season activity performed at Colorado State University (CSU) by Dr. Bill Gray's team (colored squares) and Tropical Storm Risk, Inc. (TSR, colored lines). The skill is measured by the Mean Square Skill Score (MSSS), which looks at the error and squares it, then compares the percent improvement the forecast has over a climatological forecast of 10 named storms, 6 hurricanes, and 2 intense hurricanes. TS=Tropical Storms, H=Hurricanes, IH=Intense Hurricanes, ACE=Accumulated Cyclone Energy, NTC=Net Tropical Cyclone Activity. Image credit: TSR.

August 2009 Atlantic hurricane season forecast from Tropical Storm Risk, Inc.
The British private forecasting firm Tropical Storm Risk, Inc. (TSR) also issued a new forecast today, and have increased their numbers by 20% from their June and July forecasts. TSR is also calling for a near-average season, predicting 12.6 named storms, 6.5 hurricanes, 2.8 intense hurricanes, and an Accumulated Cyclone Energy (ACE) 103% of average. Their June forecast called for 10.9 named storms, 5.2 hurricanes, 2.2 intense hurricanes, and an Accumulated Cyclone Energy (ACE) 72% of average. The storm numbers are slightly above the 50-year average of 10 named storms, 6 hurricanes, and 2 intense hurricanes. TSR predicts a 40% chance of an above-average season, 44% chance of a near-average season, and a 19% chance of a below-average season, as defined by ACE index. TSR rates their skill level as 51% above chance at forecasting the number of named storms, 60% skill for hurricanes, and 44% skill for intense hurricanes. These are far higher skill numbers than the June ones: 26% above chance at forecasting the number of named storms, 15% skill for hurricanes, and 19% skill for intense hurricanes.

TSR projects that 3.8 named storms will hit the U.S., with 1.6 of these being hurricanes. The averages from the 1950-2008 climatology are 3.2 named storms and 1.5 hurricanes. Their skill in making these August forecasts for U.S. landfalls is 25% above chance. In the Lesser Antilles Islands of the Caribbean, TSR projects 1.1 named storms, 0.5 of these being hurricanes. Climatology is 1.1 named storms and 0.5 hurricanes.

TSR cites one main factor for their increased forecast: higher sea surface temperatures than expected over the tropical Atlantic, due to the fact that the trade winds over the Atlantic should be slower than originally anticipated. Faster than average trade winds create less spin for developing storms, and allow the oceans to cool down, due to increased mixing of cold water from the depths and enhanced evaporational cooling.

The CSU and TSR groups are done making forecasts for the coming hurricane season, but NOAA is still due to put out an August update.

I'll have an update on Wednesday.
Jeff Masters

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1372. IKE
Looks like that AOI is moving almost due west.

Yellow circle?
Member Since: June 9, 2005 Posts: 23 Comments: 37860
convection is on the increase. low level clouds are streaming to the area of low pressure, indicative of good low level convergence. the increasing 850mb vortcity is also indicative of a system trying to organise
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Can someone please post a good link to the ECMWF model?
Member Since: August 28, 2006 Posts: 6 Comments: 2899
1369. KEEPEROFTHEGATE (Mod)
Quoting TampaSpin:
Looks like the AOI went poof over nite. Not unexpected when embedded in the ITCZ. Still come energy there! Lets see what happens as it continues West. A circulation is observed out of the ITCZ near the AOI.
yep the great poofer atl back to quiet for now
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Quoting cg2916:

I don't know, but it won't make much of a difference unless shear relaxes in the waters.

we will see if it extends more
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Looks like the AOI went poof over nite. Not unexpected when embedded in the ITCZ. Still come energy there! Lets see what happens as it continues West. A circulation is observed out of the ITCZ near the AOI.
Member Since: September 2, 2007 Posts: 179 Comments: 20448
Ridge will build near the east coast.

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Quoting weatherwatcher12:
Does anyone notice the shear dropping near Cuba, Jamaica and Haiti. It has been growing progressively bigger with each update. What is the cause?

? any body
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1364. KEEPEROFTHEGATE (Mod)
Quoting Claudette1234:
Felicia gets Major Hurricane status

will see the next models to see tracks and force


059

WHXX01 KMIA 050728

CHGE77

TROPICAL CYCLONE GUIDANCE MESSAGE

NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL

0728 UTC WED AUG 5 2009



DISCLAIMER...NUMERICAL MODELS ARE SUBJECT TO LARGE ERRORS.

PLEASE REFER TO NHC OFFICIAL FORECASTS FOR TROPICAL CYCLONE

AND SUBTROPICAL CYCLONE INFORMATION.



EAST PACIFIC OBJECTIVE AIDS FOR



TROPICAL CYCLONE FELICIA (EP082009) 20090805 0600 UTC



...00 HRS... ...12 HRS... ...24 HRS. .. ...36 HRS...

090805 0600 090805 1800 090806 0600 090806 1800



LAT LON LAT LON LAT LON LAT LON

BAMS 13.1N 127.8W 14.2N 129.4W 15.4N 130.8W 16.6N 132.3W

BAMD 13.1N 127.8W 14.0N 129.6W 15.1N 131.0W 15.9N 132.5W

BAMM 13.1N 127.8W 14.0N 129.4W 15.1N 130.8W 16.1N 132.3W

LBAR 13.1N 127.8W 14.3N 129.7W 15.8N 131.7W 17.1N 133.7W

SHIP 85KTS 98KTS 104KTS 103KTS

DSHP 85KTS 98KTS 104KTS 103KTS



...48 HRS... ...72 HRS... ...96 HRS. .. ..120 HRS...

090807 0600 090808 0600 090809 0600 090810 0600



LAT LON LAT LON LAT LON LAT LON

BAMS 17.8N 133.9W 20.1N 138.8W 21.7N 144.8W 22.6N 151.0W

BAMD 16.6N 134.3W 17.9N 138.4W 19.0N 143.2W 20.0N 147.4W

BAMM 17.0N 134.0W 18.9N 138.3W 20.3N 143.4W 21.4N 148.2W

LBAR 18.1N 135.6W 19.2N 139.6W 19.2N 144.4W 19.0N 149.1W

SHIP 98KTS 82KTS 65KTS 50KTS

DSHP 98KTS 82KTS 65KTS 50KTS



...INITIAL CONDITIONS...

LATCUR = 13.1N LONCUR = 127.8W DIRCUR = 295DEG SPDCUR = 10KT

LATM12 = 12.2N LONM12 = 126.1W DIRM12 = 288DEG SPDM12 = 10KT

LATM24 = 11.9N LONM24 = 123.5W

WNDCUR = 85KT RMAXWD = 25NM WNDM12 = 65KT

CENPRS = 975MB OUTPRS = 1008MB OUTRAD = 200NM SDEPTH = D

RD34NE = 75NM RD34SE = 60NM RD34SW = 45NM RD34NW = 60NM



$$

NNNN
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The area in the CATL is beginning to be some iterest. with the 850mb voticity increasing, then the area will be monitored for signs of cyclogenesis.
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Quoting Claudette1234:


MAJOR HURRICANE FELICIA

08EFELICIA.100kts-960mb-137N-1283W


Pretty Impressive.
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Felicia gets Major Hurricane status

will see the next models to see tracks and force
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MAJOR HURRICANE FELICIA

08EFELICIA.100kts-960mb-137N-1283W
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1357. cg2916
Quoting weatherwatcher12:
Does anyone notice the shear dropping near Cuba, Jamaica and Haiti. It has been growing progressively bigger with each update. What is the cause?

I don't know, but it won't make much of a difference unless shear relaxes in the waters.
Member Since: December 21, 2007 Posts: 13 Comments: 3046
1356. cg2916
That low doesn't look like much on the NOGAPS, just a closed low with not much conmvection.
Member Since: December 21, 2007 Posts: 13 Comments: 3046
Does anyone notice the shear dropping near Cuba, Jamaica and Haiti. It has been growing progressively bigger with each update. What is the cause?
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1354. cg2916
Quoting IKE:
That low is the AOI for today in the Atlantic.

I guess it is.
Member Since: December 21, 2007 Posts: 13 Comments: 3046
1353. cg2916
Quoting IKE:


Seems like it showed it as a low...with some convection. Nothing major(hurricane+) on it, like it's showing now in the east-PAC systems.

NOGAPS has done pretty good in 2009. It's showing the 850mb vorticity near 35W strengthening...Link


Ok, thanks. I wanted to know what model does best this season. Looks like I'm watching the NOGAPS more, with the GFDL, of course, that's always pretty reliable. The GFS and CMC seem to be very bullish this season.
Member Since: December 21, 2007 Posts: 13 Comments: 3046
1352. IKE
That low is the AOI for today in the Atlantic.
Member Since: June 9, 2005 Posts: 23 Comments: 37860
Blog Update
Reflector site for those at work, which includes Weather456, daily update.


AOI

AOI
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1350. IKE
Quoting cg2916:
IKE, do you remember if the ECMWF forecasted TD 1?


Seems like it showed it as a low...with some convection. Nothing major(hurricane+) on it, like it's showing now in the east-PAC systems.

NOGAPS has done pretty good in 2009. It's showing the 850mb vorticity near 35W strengthening...Link

Member Since: June 9, 2005 Posts: 23 Comments: 37860
Felicia will not threaten hawaii it will take in cool waters and weaken to ts or td.
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00Z



06Z

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the famous hurricane which hit Hawaii was INOKI
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1346. cg2916
IKE, do you remember if the ECMWF forecasted TD 1?
Member Since: December 21, 2007 Posts: 13 Comments: 3046
for once we are in agreement. as one of our bloggers might " i concur " LOL
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1344. IKE
Quoting BDAwx:
is this the latest date for the first named storm for the decade?


Looks like the answer is yes...

Member Since: June 9, 2005 Posts: 23 Comments: 37860
Quoting stoormfury:
the Hawaian islands hardly get hit by hurricanes. sometime in recent history they received a pounding from a hurricane. the name i can't recall at this time
started with a (I) i believe
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1341. IKE
Quoting stoormfury:
ok IKE i have seenit on the surface chart. what i have also seen is that the northwest movement is due to a weakness in the steering current along 33-34w. there after the ridge flattens out to allow it to resume a west track, thereby avoiding the shear to the north


If it goes back west, maybe it has a chance. NOGAPS has that vorticity getting stronger.

It does look headed just north of west, to me.
Member Since: June 9, 2005 Posts: 23 Comments: 37860
1339. BDAwx
is this the latest date for the first named storm for the decade?
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1338. IKE
Quoting sporteguy03:


Hey Ike! I get what you are saying, but at the same time if they show nothing or the ECMWF for that matter are the models still right though all the time? :)


No, but it's been correct so far.
Member Since: June 9, 2005 Posts: 23 Comments: 37860
OK,
Why is the SST graphic moving backward in time? It is between July 09 and May 09. Is there a reason not to put the early date first? Do they mean July 08? All the subtext is consistent with a 2 month period but why put the end date first?
I'm not usually type A, but reverse time messes with me.
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Quoting IKE:


And I got raked over the coals by someone over my comment.

I see the yellow circle is gone.

I guess the wishcasters can now head back into hiding until the real season starts.

GFS...wrong.
CMC...wrong.


Hey Ike! I get what you are saying, but at the same time if they show nothing or the ECMWF for that matter are the models still right though all the time? :)
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the Hawaian islands hardly get hit by hurricanes. sometime in recent history they received a pounding from a hurricane. the name i can't recall at this time
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Quoting KEEPEROFTHEGATE:
UW - CIMSS
ADVANCED DVORAK TECHNIQUE
ADT-Version 7.2.3
Tropical Cyclone Intensity Algorithm

----- Current Analysis -----
Date : 05 AUG 2009 Time : 113000 UTC
Lat : 13:46:28 N Lon : 128:17:19 W


CI# /Pressure/ Vmax
5.1 / 969.6mb/ 92.4kt


Final T# Adj T# Raw T#
(3hr avg)
5.0 4.3 4.3

Latitude bias adjustment to MSLP : +1.6mb

Center Temp : -54.4C Cloud Region Temp : -75.5C

Scene Type : UNIFORM CDO CLOUD REGION

Positioning Method : SPIRAL ANALYSIS

Ocean Basin : EAST PACIFIC
Dvorak CI > MSLP Conversion Used : ATLANTIC

Tno/CI Rules : Constraint Limits : NO LIMIT
Weakening Flag : ON
Rapid Dissipation Flag : OFF

****************************************************




Yea it shows that it is weakening but that is because the eye is not clearly defined right now once we get a clearly defined eye we will get a more accurate reading
Member Since: August 1, 2006 Posts: 28 Comments: 3716
ok IKE i have seenit on the surface chart. what i have also seen is that the northwest movement is due to a weakness in the steering current along 33-34w. there after the ridge flattens out to allow it to resume a west track, thereby avoiding the shear to the north
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Hawaii Five-O and hr puff n stuff greatest shows back in the 70s.
Member Since: March 19, 2009 Posts: 0 Comments: 1421
1331. KEEPEROFTHEGATE (Mod)
UW - CIMSS
ADVANCED DVORAK TECHNIQUE
ADT-Version 7.2.3
Tropical Cyclone Intensity Algorithm

----- Current Analysis -----
Date : 05 AUG 2009 Time : 113000 UTC
Lat : 13:46:28 N Lon : 128:17:19 W


CI# /Pressure/ Vmax
5.1 / 969.6mb/ 92.4kt


Final T# Adj T# Raw T#
(3hr avg)
5.0 4.3 4.3

Latitude bias adjustment to MSLP : +1.6mb

Center Temp : -54.4C Cloud Region Temp : -75.5C

Scene Type : UNIFORM CDO CLOUD REGION

Positioning Method : SPIRAL ANALYSIS

Ocean Basin : EAST PACIFIC
Dvorak CI > MSLP Conversion Used : ATLANTIC

Tno/CI Rules : Constraint Limits : NO LIMIT
Weakening Flag : ON
Rapid Dissipation Flag : OFF

****************************************************


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1330. IKE
Quoting Chicklit:
Crow pie isn't too bad with some strong coffee...It's the bones that really bother me!


You getting a helping of crow?



Here's the good news on Felicia from the latest discussion.....

"THE ENVIRONMENT AROUND FELICIA REMAINS CONDUCIVE FOR FURTHER
STRENGTHENING. THE MID-LEVEL CUT-OFF LOW NEAR CALIFORNIA IS
INDUCING DIFFLUENCE ALOFT TO THE NORTH OF FELICIA...AND IT APPEARS
THAT AN OUTFLOW JET MAY BE FORMING. VERTICAL SHEAR IS EXPECTED TO
REMAIN LIGHT OVER THE NEXT FIVE DAYS...AND OCEANIC HEAT CONTENT
SHOULD REMAIN SUFFICIENT FOR AT LEAST THE NEXT 36 HOURS. THE
NORTHWARD SHIFT IN THE TRACK FORECAST PUTS FELICIA OVER 24-25
DEGREES CELSIUS WATER AFTER 48 HOURS...AND THE NEW OFFICIAL
INTENSITY FORECAST ACCOUNTS FOR THIS BY SHOWING FASTER WEAKENING
THAN WAS INDICATED IN THE PREVIOUS FORECAST.
IF FELICIA STAYS A
LITTLE FARTHER SOUTH...IT MIGHT BE ABLE TO MAINTAIN ITS INTENSITY
FOR A LONGER PERIOD OF TIME.

FORECAST POSITIONS AND MAX WINDS

INITIAL 05/0900Z 13.4N 128.2W 90 KT
12HR VT 05/1800Z 14.1N 129.5W 100 KT
24HR VT 06/0600Z 15.1N 131.2W 105 KT
36HR VT 06/1800Z 16.1N 132.8W 100 KT
48HR VT 07/0600Z 17.1N 134.6W 90 KT
72HR VT 08/0600Z 18.5N 139.0W 75 KT
96HR VT 09/0600Z 19.0N 144.5W 65 KT
120HR VT 10/0600Z 19.0N 150.0W 50 KT"
Member Since: June 9, 2005 Posts: 23 Comments: 37860
Felicia continues to



The eyewall is starting to get the -80 deg convection on the west side. If the west side gets like the east side and the eye gets even clearer then ADT numbers will likely hit 6.5 or even up to 7.0
Member Since: August 1, 2006 Posts: 28 Comments: 3716
1326. futuremet 12:03 PM GMT on August 05, 2009
Who wants to go to Hawaii?


lol, i do for sure...but you know TWC is going to go non stop action over this....break out the goggles Cantore

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Crow pie isn't too bad with some strong coffee...It's the bones that really bother me!
Member Since: July 11, 2006 Posts: 14 Comments: 11424
Who wants to go to Hawaii?

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1325. IKE
Quoting stoormfury:
i might be wrong and stand to be corrected.
iam seeing a small cyclonic turning near 11N 34 W. Looking at the QS of the area this morning it appears there might be a weak surface refletion


I found this on that area, from the latest tropical weather discussion....

"A 1012 MB LOW PRESSURE CENTER IS NEAR 11N33W...MOVING NORTHWEST
15 KT. SHOWERS AND THUNDERSTORMS FROM 12N TO 13N BETWEEN 32W AND
35W."

NW is drier air and shear increasing north of 16N.
Member Since: June 9, 2005 Posts: 23 Comments: 37860
1324. Relix
This little brave wave could do a Jeanne and become a storm just as she approaches the windward islands. Who knows, I just know it doesn't look impressive at all right now.
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1319. Shucks, you corrected it. LOL
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1322. IKE
Quoting futuremet:


Not for long bud...



We'll see what happens.
Member Since: June 9, 2005 Posts: 23 Comments: 37860

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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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