Unprecedented Hurricane Tomas pounding the Lesser Antilles

By: Dr. Jeff Masters , 3:38 PM GMT on October 30, 2010

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Hurricane Tomas, an unprecedented Lesser Antilles hurricane for so late in the season, is bearing down on the islands of St. Lucia and St. Vincent with Category 1 winds of 75 mph. Recent radar imagery from the Martinique radar shows that Tomas is still in the organizing stage, with an eyewall that just closed off, and a weak area of echoes on the south side, due to modest wind shear of 10 knots caused by southerly upper-level winds. The Hurricane Hunters reported top surface winds in the northern eyewall near 75 mph. St.Lucia figures to get the worst blow from Tomas, as this island will experience the strong right-front quadrant of the storm--the north eyewall. Winds on the island were sustained at 46 mph, gusting to 67 mph, at 11am EDT. Winds at Barbados peaked at 37 mph, gusting to 56 mph, early this morning, and the pressure bottomed out at 994 mb. Satellite loops of Tomas show a large and well-organized Cape Verdes-type hurricane, with good upper level outflow on all sides except the south, and an impressive amount of heavy thunderstorm activity. This is a very dangerous hurricane that is just beginning to get going. You can follow the progress of Tomas through the islands today with our wundermap zoomed in on St. Lucia.


Figure 1. Morning radar image from the Martinique radar shows the eye of Tomas moving between the islands of St, Lucia to the north and St. Vincent and the Grenadines to the south. The southern portion of the eyewall had just closed off with this image. Image credit: Meteo France.

Intensity forecast for Tomas
Now that the eyewall of Tomas has completely closed off, a period of steady and possibly rapid intensification lasting until Sunday afternoon is likely. The intensification rate may then be slowed by an increasing flow of southwesterly upper-level winds, which are expected to bring dry air and a moderate 15 - 20 knots of wind shear to Tomas Sunday through Tuesday, according to the latest SHIPS model forecast. Shear is then expected to relent, allowing more intensification on Wednesday. Water temperatures are a record warm 29.5°C and the Tropical Cyclone Heat Potential--a measure of the total heat content of the ocean--is a very high 100 kJ/cm^2, which is very favorable for rapid intensification. I expect the Tomas will strengthen to a Category 3 or 4 hurricane by Wednesday.


Figure 2. Hurricane specialists Robbie Berg (background) and Dan Brown (foreground) discuss the latest data on Tomas last night at the National Hurricane Center.

Track forecast for Tomas
The computer models have come into better agreement this morning that after Tomas reaches the central Caribbean 4 - 5 days from now, a turn to the north or northeast is likely, in response to a strong trough of low pressure expected to develop over the Eastern U.S. The exact timing of this turn to the north or northeast is difficult to predict at this time, as steering currents will be weak in the Caribbean after Tomas passes through the Lesser Antilles today and Sunday. At this time, is appears that the Dominican Republic and Haiti are most at risk from a strike by Tomas, though the storm could move as far west as Jamaica, or as far east as the northern Lesser Antilles Islands.


Figure 3. Hurricane specialist Dan Brown computes Tomas' radius of tropical storm force winds using the old-fashioned paper track plot and dividers technique. Hurricane specialists at NHC commonly use a paper track plot to mark all storm center fixes and compute the current motion of the storm. A storm's current heading and speed in NHC advisories is usually a 12-hour average of the motion up until the final fix position.

Tomas, Shary, and the 2010 hurricane season in perspective
Tomas' formation ties 2010 with 1995 and 1887 for 3rd place for most number of named storms in an Atlantic hurricane season. Only 2005 (28 named storms) and 1933 (21 named storms) were busier. Atlantic hurricane records go back to 1851, though there were likely many missed named storms prior to the beginning of satellite coverage in the mid-1960s. The intensification of Shary and Tomas into hurricanes today brings the total number of hurricanes this season to twelve, tying 2010 with 1969 and 1887 for second place for most hurricanes in a season. The record is held by 2005 with fifteen hurricanes, and I don't think we'll beat that record this year!

The formation of Tomas so far south and east this late in the season is unprecedented in the historical record; no named storm has ever been present east of the Lesser Antilles (61.5°W) and south of 12°N latitude so late in the year. Hurricane Six of 1896 came close--it was also a tropical storm south of 12°N and east of 61.5°W on October 29, but nine hours earlier in the day. That storm recurved to the north and missed the Lesser Antilles. Tomas' track through the southern Lesser Antilles so late in the year is unprecedented. There have been only two other tropical storms that formed after October 15 south of 12°N and east of 61.5°W: Hurricane Jose, which was a tropical storm in that region on October 18, 1999, and Tropical Storm Nicolas, on October 16, 2003. Tomas most reminds me of a storm I flew into with the Hurricane Hunters--Hurricane Joan of 1988, which was a tropical storm on October 14 near Tomas' current location, and later strengthened into a Category 4 hurricane that hit Nicaragua. According to Chenoweth (2008), Tomas is the first tropical storm to cross through the Lesser Antilles Islands south of 16°N this late in the year since 1724. In that year, a tropical storm on 12 November crossed the islands at 13.7°N 61.5°W, and later became a hurricane that affected Jamaica. There was also a hurricane on 30 October 1671 that crossed 61.5°W at 13.3°N, and did damage on Barbados.

Another unusual aspect of Tomas' formation is that we now have two simultaneous hurricanes in the Atlantic Ocean on October 30. There has been only one hurricane season since 1851 that had had two simultaneous hurricanes later in the year--1932, when Hurricane Ten and Hurricane Eleven both existed November 7 - 10. Today is also the 5th latest date in the season that there have been two simultaneous named storms in the Atlantic. The record was set way back in 1887, when Hurricane Eighteen and Tropical Storm Nineteen were both active on December 8. There were three years that had simultaneous November named storms: 1932, 1961, and 2001.

References
Chenoweth, M. and D. Divine (2008), "A document-based 318-year record of tropical cyclones in the Lesser Antilles, 1690-2007", Geochemistry, Geophysics, Geosystems, 9, doi:10.1029/2008GC002066.

Next update
I'll have more on Sunday by 3pm EDT. I'm headed home to Michigan today, after a very valuable week here at the National Hurricane Center. The experience gave me a new appreciatation for just how good the forecasters are at what they do. NHC's hurricane experts are truly world-class, and we are very fortunate to have such a talented group of hard-working forecasters keeping us informed on the dangers we face from Atlantic hurricanes.

Jeff Masters

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1543. scott39
Quoting weatherwatcher12:
What is with this turn?
Is that a "gradual turn"???
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Quoting IKE:


Strong trough is going to kick this system north.

I know that, but the trough looks like it's still chugging eastward.
Member Since: May 16, 2009 Posts: 1 Comments: 1231
1541. JRRP
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That really sucks for Haiti. They've been through a lot this year. They defiantly don't need a major hurricane.
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1539. roleli
Quoting WeatherNerdPR:

O_O


Christopher from St. Lucia had mentioned this bridge Storm Carib St Lucia Reports
"only bridge over the Choc river is being undercut by the river."

"Without that vital bridge, traffic between the north and south will have to go several miles inland and wind along a narrow and hilly secondary road.... Oh Joy!!! :-("
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removed
Member Since: May 16, 2009 Posts: 1 Comments: 1231
1537. IKE
Quoting weatherwatcher12:
What is with this turn?


Strong trough is going to kick this system north.
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1536. scott39
I think if Tomas weakens enough and goes more WSW on Tuesday for awhile missing the trough, It might---Just might head towards CA/Yucatan. Which they also do not need it.
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1535. IKE
...TOMAS WEAKENS SLIGHTLY...
11:00 AM AST Sun Oct 31
Location: 14.0°N 63.7°W
Max sustained: 90 mph
Moving: WNW at 9 mph
Min pressure: 986 mb
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What is with this turn?
Member Since: May 16, 2009 Posts: 1 Comments: 1231
...TOMAS WEAKENS SLIGHTLY...

SUMMARY OF 1100 AM AST...1500 UTC...INFORMATION
-----------------------------------------------
LOCATION...14.0N 63.7W
ABOUT 180 MI...290 KM W OF ST. LUCIA
ABOUT 345 MI...550 KM SSE OF SAN JUAN PUERTO RICO
MAXIMUM SUSTAINED WINDS...90 MPH...150 KM/HR
PRESENT MOVEMENT...WNW OR 285 DEGREES AT 9 MPH...15 KM/HR
MINIMUM CENTRAL PRESSURE...986 MB...29.12 INCHES


FORECAST DISCUSSION:

000
WTNT41 KNHC 311444
TCDAT1
HURRICANE TOMAS DISCUSSION NUMBER 10
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL212010
1100 AM AST SUN OCT 31 2010

DEEP CONVECTION ASSOCIATED WITH TOMAS HAS GENERALLY DECREASED DURING
THE LAST FEW HOURS AND BANDING FEATURES HAVE BECOME A LITTLE LESS
ORGANIZED. IN ADDITION...RECENT MICROWAVE IMAGES NO LONGER SHOW AN
EYE. BASED ON THIS...THE INITIAL WIND SPEED IS LOWERED TO 80
KT...WHICH IS A BLEND OF THE LATEST SUBJECTIVE AND OBJECTIVE
SATELLITE INTENSITY ESTIMATES. THE NEXT AIR FORCE RESERVE
RECONNAISSANCE AIRCRAFT SHOULD PROVIDE A BETTER ASSESSMENT OF THE
INTENSITY EARLY THIS AFTERNOON.

THE INITIAL MOTION ESTIMATE IS 285/8. A GENERAL WESTWARD TO
WEST-NORTHWESTWARD MOTION AT ABOUT THE SAME SPEED IS EXPECTED
DURING THE NEXT COUPLE OF DAYS AS MID-LEVEL RIDGING REMAINS IN
PLACE TO THE NORTH OF TOMAS. SOME OF THE MODELS EVEN SHOW A SOUTH
OF WEST MOTION DURING THAT TIME. IN ABOUT 3 DAYS...THE CYCLONE IS
EXPECTED TO SLOW DOWN AS A LARGE MID- TO UPPER-LEVEL LOW MOVES OVER
THE GULF OF MEXICO...CAUSING THE RIDGE TO ERODE. TOMAS IS FORECAST
TO GRADUALLY TURN TOWARD THE NORTH IN 4 TO 5 DAYS AS IT FEELS THE
INFLUENCE OF SOUTHERLY FLOW TO THE EAST OF THE TROUGH. THE LATEST
MODEL GUIDANCE HAS CHANGED LITTLE FROM THE LAST CYCLE...AND THE
OFFICIAL FORECAST IS ESSENTIALLY AN UPDATE OF THE PREVIOUS TRACK.

ALTHOUGH TOMAS LIES OVER AN AREA OF HIGH OCEANIC HEAT CONTENT...
MODERATE SOUTHWESTERLY SHEAR AND SOME MID-LEVEL DRY AIR AS SHOWN BY
MODEL CROSS SECTIONS COULD BE A LIMITING FACTOR FOR INTENSIFICATION
DURING THE NEXT COUPLE OF DAYS. IN FACT...SEVERAL OF THE RELIABLE
MODELS...INCLUDING THE GFS...ECMWF...AND GFDL...SHOW THE VORTEX
TILTING TO THE NORTHEAST WITH HEIGHT. THIS RESULTS IN THE
WEAKENING OF THE HURRICANE IN THOSE MODELS DURING THE NEXT COUPLE
OF DAYS. THE OFFICIAL FORECAST HAS BEEN NUDGED DOWNWARD THROUGH 48
HOURS BUT REMAINS HIGHER THAN ALL OF THE INTENSITY GUIDANCE DURING
THAT TIME. A MORE FAVORABLE UPPER-LEVEL WIND PATTERN IS EXPECTED
DURING THE 3 TO 5 DAY TIME FRAME...AND THAT SHOULD ALLOW FOR STEADY
STRENGTHENING.

ALTHOUGH TROPICAL STORM WARNINGS FOR THE WINDWARD ISLANDS HAVE BEEN
DISCONTINUED...THE THREAT OF HEAVY RAINFALL IS EXPECTED TO CONTINUE
OVER MUCH OF THE LESSER ANTILLES THROUGH TONIGHT.

FORECAST POSITIONS AND MAX WINDS

INITIAL 31/1500Z 14.0N 63.7W 80 KT
12HR VT 01/0000Z 14.5N 65.1W 75 KT
24HR VT 01/1200Z 14.9N 67.2W 75 KT
36HR VT 02/0000Z 15.0N 69.1W 75 KT
48HR VT 02/1200Z 15.0N 70.6W 75 KT
72HR VT 03/1200Z 15.0N 72.5W 85 KT
96HR VT 04/1200Z 15.5N 73.5W 95 KT
120HR VT 05/1200Z 17.0N 73.5W 100 KT

$$
FORECASTER CANGIALOSI/BROWN
Member Since: September 2, 2009 Posts: 130 Comments: 21091
Tomas is the worst looking 100+mph storm I've ever seen.


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1530. scott39
Quoting BahaHurican:
Ah... got 5 more minutes grace time... lol

I wouldn't think of that area N of PR / DR as a dead zone... too many storms intensify in that area.

I guess I was thinking about the Twaves, where nothing that's not already an established TC will get going... but wouldn't the same factors that inhibit formation also inhibit / moderate intensification, esp. RI?
Yes, The Eastern Caribbean Sea has had a history of killing developing TCs and developed TCs. That is why there is a "grave yard" there. Tomas will go thru the Gauntlet getting beat up, and then come back before landfall.
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Quoting CaicosRetiredSailor:
Photo of
Choc bridge collapsed

http://twitpic.com/32m6dl

O_O
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1528. KEEPEROFTHEGATE (Mod)
lets hope tomas
turns into poof
i mean puff
the magic dragon
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Photo from St. Lucia:
Choc bridge collapsed

http://twitpic.com/32m6dl

Share photos on twitter with Twitpic
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Could Tomas trayectory include Oriental Cuba?...
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Ah... got 5 more minutes grace time... lol

I wouldn't think of that area N of PR / DR as a dead zone... too many storms intensify in that area.

I guess I was thinking about the Twaves, where nothing that's not already an established TC will get going... but wouldn't the same factors that inhibit formation also inhibit / moderate intensification, esp. RI?
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1523. scott39
Quoting scott39:
Actually its the Eastern Caribbean.
sea
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1522. pottery
Trinidad weather now-
temp 75F
humidity 100%
light rain/heavy overcast
wind calm
pressure 1012 steady
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Good Morning. Does anyone have a link to a long radar loop from the Lesser Antilles?
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1520. scott39
Quoting Cat5hit:
Baha - Dead zone is North of PR and Hispaniola... "Hurricane Graveyard" is what it is normally referred to.

Actually its the Eastern Caribbean.
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1519. scott39
Quoting BahaHurican:
1) Isn't this the "Dead Zone" sometimes talked about here?

2) I'm watching to see how the intensity forecast pans out, as IMO intensity's going to be the largest single factor in track forecast verifying.
Im concerned that Tomas is going to be one of those, that keeps us and the forecasters perplexed until close to landfall.
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Quoting BahaHurican:
1) Isn't this the "Dead Zone" sometimes talked about here?

2) I'm watching to see how the intensity forecast pans out, as IMO intensity's going to be the largest single factor in track forecast verifying.

It's the dead zone for waves, but is considered fertile ground for developing hurricanes.
Member Since: May 16, 2009 Posts: 1 Comments: 1231
This has been one of the more active seasons for Bermuda in a while. What are they up to after Shary, 4 hits? 5?

Anyway, I gotta go. I'll check in if at all possible around 2-3 p.m.
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Quoting stormwatcherCI:
He is expected to weaken to about 80 mph for about 24 hours or so and then to begin to intensify again.
1) Isn't this the "Dead Zone" sometimes talked about here?

2) I'm watching to see how the intensity forecast pans out, as IMO intensity's going to be the largest single factor in track forecast verifying.
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1514. roleli
Quoting stormwatcherCI:
He is expected to weaken to about 80 mph for about 24 hours or so and then to begin to intensify again.


Intensify and have it South of Haiti&South East of Jamaica in 4 1/2 days as a major storm before turns north. This is not pretty for Haiti and will certainly have us here in Jamaica holding our breath.

Interestingly Bermuda could be in for action again.
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1513. scott39
Tomas is taking a good beating this morning. It wont be enough though.
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Speaking of Haiti, I think this is a good time to remember that Portlight has a Christmas drive going on for support of its efforts there.

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Quoting SouthDadeFish:
Judging by recent satellite trends, Tomas is clearly weakening. Satellite estimates have now dropped to T4.0, and hopefully he continues to weaken.
He is expected to weaken to about 80 mph for about 24 hours or so and then to begin to intensify again.
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1510. Skyepony (Mod)
Tomas~Average Position Error (nm) for models
model Error Trend 24hr Error 48hr Error 72hr Error Day 4 Error Day 5 Error
KHRM DECREASING 29.6 -1 -1 -1 -1
MM5E DECREASING 34 -1 -1 -1 -1
CMC CONSTANT 36.9 83.9 124.3 -1 -1
GFDL INCREASING 41.3 -1 -1 -1 -1
HWRF DECREASING 44.6 96.3 140 -1 -1
LBAR INCREASING 75.2 87.6 88.2 -1 -1
OFCL INCREASING 77.9 115.5 -1 -1 -1
MM5B DECREASING 94.1 144.3 140.8 -1 -1
BAMD CONSTANT 97.7 199.5 277.3 -1 -1
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1509. scott39
Ike needs to sharpen up one of those daggers of death for TCs and pierce the heart of Tomas! Looks like he shot an arrow at it this morning. LOL
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Quoting afj3:

One's chain can only be yanked if the chainholder allows his or her chain to be yanked....
True. But u have to recognise WHEN ur chain is being yanked.... lol

BTW, which part of FL are u in? With the way things are shaping up, FL looks like it's missed the bullet, but I'm paranoid enough to imagine a scenario where Tomas shoots the gap between Haiti and Cuba, regains strength over the Eastern/Central Bahamas, then shoots off to the NW, making a direct hit over New Providence, Grand Bahama, and Port St. Lucie.... not a laughing matter, but definitely a potential nightmare for some of us.....
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1507. wxhatt
Quoting weatherguy03:
Tropical Update Oct. 31st. 2010


Thanks for the update Bob.
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1506. Grenada
Stronger gusty winds now with a smattering of thunder, very thick clouds.
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Quoting SouthDadeFish:
Read about the technique here

Ah, thanks.
Member Since: May 16, 2009 Posts: 1 Comments: 1231
Quoting weatherwatcher12:

I thought it indicated two different agencies disagreeing.
Read about the technique here
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Any confirmation on whether someone was on the Choc bridge when it failed?
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1502. scott39
Quoting weatherguy03:
Tropical Update Oct. 31st. 2010
Thanks for sharing your knowledge.
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P451: Thank you for crystallizing the moral dilemma many may be struggling with (comment 1458).
Learned much from your #1474 comment. Thanks so much!
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Quoting SouthDadeFish:
Which means it appears as 4.0 but is still generating winds of 4.5.

I thought it indicated two different agencies disagreeing.
Member Since: May 16, 2009 Posts: 1 Comments: 1231
Quoting KEEPEROFTHEGATE:
i know nothing iam an expert at nothing


Not true, your from Toronto, so that means your an expert at shovelling snow :)
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1498. afj3
Quoting Orcasystems:


If you want to learn the basics, and later in his lessons the more complicated parts.. go to this Blog.

quasigeostropic's WunderBlog

Its very easy to understand and follow.


Thanks! Will check it out now....
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Quoting KEEPEROFTHEGATE:
Wow. Can't get much worst than that for Haiti... is that GFS?

And still wondering if that kind of response to the trough is likely or warrented...
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Quoting weatherwatcher12:

Actually it's T4.0/4.5.
Which means it appears as 4.0 but is still generating winds of 4.5.
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Quoting largeeyes:
Looks like the Choc bridge did indeed fail last night.


Link
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1494. scott39
Quoting wxhatt:
The ACE index has been on the high side this year (151.4 thus far). Thankfully impacts on the US mainland have been minimal. Let's hope that it remains that way as we wind down the season.

As I had said early on, this years analog package looked to resemble the 1995 hurricane season in regard to storm tracks.

2010


1995
Thats a good year to compare. I havent been able to find any other year with this many TCs and not a hurricane strike on the lower 48.
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Quoting afj3:

I realize that many are not professional meteorologists but they do know their weather. Some have shared their knowledge and were friendly with me and other people while others boast about how brilliant they are and how tech-savvy they are but won't a): share the hypotheses and work behind their conclusions and b): where they get access to models and other technology and c): patronize others for not being up to speed as they are. I would love to be able to forecast as an armchair-amateur--I just need some help....


If you want to learn the basics, and later in his lessons the more complicated parts.. go to this Blog.

quasigeostropic's WunderBlog

Its very easy to understand and follow.
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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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