Atlanta tornado one the most damaging on record

By: Dr. Jeff Masters , 2:24 PM GMT on March 17, 2008

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The strong EF2 tornado that smashed through downtown Atlanta at 9:40 pm Friday night is a reminder that the U.S. is potentially vulnerable to a very high death toll from a violent tornado hitting a major city. Friday's tornado, with a width of 200 yards, path length of 6 miles, and winds up to 130 mph, was strong enough to cause an estimated $150-$200 million in damage to downtown Atlanta. Only 16 tornadoes during the 20th century caused inflation-adjusted damage more than $200 million (Brooks and Doswell, 2000), so the Atlanta tornado is one of the most damaging of all time. Fortunately, no one was killed, although at least 27 people were injured, one seriously.

As unlucky as Atlanta was to have its first tornado ever to hit the downtown area, the city was extremely fortunate that the tornado was not not stronger. What would have happened if a clone of the strongest tornado on record--the May 3, 1999 Bridgecreek-Moore F5 tornado--had hit Atlanta? According to tornado researcher Josh Wurman of the Center for Severe Weather Research in Boulder and three co-authors in a paper published in the January 2007 issue of the Bulletin of the American Meteorological Society, the toll would have been staggering--14,900 deaths and tens of billions in damage. I discussed their findings in an April 2007 blog.

However, three tornado researchers, led by Harold Brooks of the National Severe Storms Laboratory, challenged these numbers in a January 2008 article in the Bulletin of the American Meteorological Society. They argued that Wurman et al. overestimated the potential deaths from such a storm by a factor of 100, and a death toll nearer to 150 would be more reasonable. They stated:

Given that the highest death toll in a tornado in U.S. history is 695 in the Tri-State tornado of 1925, and that the last death toll of greater than 100 was in 1953, the validity of these estimates is of some concern.

The authors conceded that a violent tornado traveling the length of a rush hour-packed freeway or hitting a sports stadium filled with spectators could generate much higher death tolls. Wurman et al. responded to the criticism by defending their death toll estimates:

We acknowledge that historical tornadoes have not caused the level of fatalities estimated in our paper. However, considering that tornadoes are relatively rare and that dense population in urban and suburban neighborhoods in the United States is a relatively recent but growing phenomenon, the historical record is too short to indicate the range of possible events.

Considering that Friday's Atlanta tornado hit the Georgia Dome stadium when it was packed with 16,000 people watching an SEC tournament basketball game, I think that both groups of researchers would agree that a death toll in the thousands was quite possible had the Atlanta tornado been an EF5.


Figure 1. Doppler winds image of the March 14, 2008, Atlanta, Georgia EF2 tornado. Note the region just northwest of the city showing blues and reds right next to each other, denoting strong winds moving both towards and away from the radar in a tight circulation. This is the signature associated with a mesocyclone--a rotating thunderstorm that commonly spawns a tornado.

More severe weather expected this week
Severe weather is expected over much of the Midwest and Southern U.S. over the next three days, in association with a strong cold front that will traverse the region. The Storm Prediction Center has placed portions of Texas, Oklahoma, Kansas, Missouri, and Arkansas under its lowest classification of potential severe weather today, "Slight Risk". The Weather Underground Severe Weather page and Tornado page are good places to go to follow this week's severe weather.

Good tornado book
For those of you interested in reading about the most violent and most damaging tornado on record, the famed 1999 Bridgecreek-Moore tornado, I recommend a reading of Nancy Mathis' book Storm Warning, which is now out in paperback. I reviewed the book in a blog last year.

Annual WeatherDance contest ready for registration!
Armchair forecasters, now's your chance to shine! WeatherDance, based on teams in the men's and women's NCAA basketball tournaments, allows players to predict which team's city will be hotter or colder on game day in each round of the Big Dance. Beginning today, players can make their forecasts at the Weather Dance Web site at: www.weatherdance.org. The site will be updated with cities promptly after NCAA seeding announcements. First round Weather Dance selections must be entered by 11:59 p.m. EST Wednesday, March 19.

"Officially, Weather Dance began as a class project to get students involved in weather forecasting, but we kept it around because it got popular. People think they can do better forecasting than the meteorologists. Well, here's their shot!" said Perry Samson, WeatherDance creator, co-founder of the The Weather Underground, Inc., and Professor in the Department of Atmospheric, Oceanic and Space Sciences at the University of Michigan.

This is the third year for the game. Last year more than 2,000 people played. Most play merely for the thrill, but many science teachers involve their classes as part of meteorology units. The winning teacher will receive an invitation and $500 to join the Texas Tech/University of Michigan Storm Chasing team this spring for a day of tornado chasing. Other winners will receive a Weather Underground umbrella or a copy of the book "Extreme Weather," by Christopher C. Burt.

Jeff Masters

Atlanta Tornado Damage (boyntonbeachboy)
Brick Bldg that was destroyed by tornado landed on this car!
Atlanta Tornado Damage
Atlanta Tornado F2 CNN CENTER (boyntonbeachboy)
The first recorded tornado hit downtown Atlanta last night causing major damage
Atlanta Tornado F2 CNN CENTER
2 inch Hail (JoyBelle)
This is some of the hail after tornadoes swept through our area today.
2 inch Hail

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82. weathermanwannabe
11:30 AM EDT on March 18, 2008
It's more like a torrant of moist air. We have had gusts of near 50 mph. this am here in Liberty, Tx.

Yeah.....While frontal related conditions have not deteriorated yet, my concern for you guys/LA is if severe weather breaks out in the overnight hours when people are not awake/as alert.......It's all about the timing of the front and how stable/unstable the air mass is as the front approaches...Please take care this evening.....
Member Since: August 8, 2006 Posts: 0 Comments: 9134
81. TEXASYANKEE43
3:14 PM GMT on March 18, 2008
80. weathermanwannabe 2:35 PM GMT on March 18, 2008
Need to keep your eyes open, and radios on, as the day/evening develops in those parts as the front approaches the warm moisture sweeping up from the Gulf...................


It's more like a torrant of moist air. We have had gusts of near 50 mph. this am here in Liberty, Tx.
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80. weathermanwannabe
9:30 AM EST on March 18, 2008
Good Morning...........All seems quiet on the Blog this morning (and is deceptively quiet over most of Texas right now) but the SPC convective outlooks keep "creeping" over towards the East for Texas/LA in the moderate risk category........Need to keep your eyes open, and radios on, as the day/evening develops in those parts as the front approaches the warm moisture sweeping up from the Gulf...................
Member Since: August 8, 2006 Posts: 0 Comments: 9134
78. Patrap
6:18 AM CDT on March 18, 2008
GOM 60 Hour Wave Forecast Model Link







Area forecast discussion
National Weather Service New Orleans la
417 am CDT Tuesday Mar 18 2008


Short term...


A very strong upper level low and associated surface low
developing over Texas will be the primary players through the
first 36 hours of the forecast. As the low deepens in Texas
today...a very strong pressure gradient between the low and a
ridge over the southeast will develop across the forecast area.
Winds are expected to exceed advisory criteria through the day
into tonight...as the low deepens and begins to approach the
region. Sustained winds of 20 to 30 miles per hour with higher gusts are
expected. Temperatures will remain about 5 to 10 degrees above
normal today as well...as the strong southerly flow off the Gulf
continues...and a thermal axis currently over East Texas advects
into the region. Skies will remain cloudy through the day...as low
and midlevel moisture pump in from the Gulf. The persistent strong
southerly winds will also drive up tides 1 to 2 feet above normal
today into early tonight. Overall probability of precipitation should remain low this
morning...as the strongest dynamic forcing remains over
Texas...but a few showers and thunderstorms could develop by late
this afternoon...and increasing positive vorticity advection and
split flow aloft develop. The highest chance for probability of precipitation will be
closer to the low over western zones.


Going into tonight...the main thrust of the low pressure system
will affect the Gulf south. A strong 120 knot jet streak should
round the base of the upper level low in Texas. As this takes
place...the upper level low should begin to take on a more
negative tilt and eject northeastward toward the arklatex region.
The corresponding surface reflection will move through the lower
Mississippi Valley into the Tennessee Valley. A fairly strong cold
front/dry line will trail the front over western Louisiana early
on and then sweep through the County Warning Area from late evening into the early
morning hours. At this time...there is a fairly strong chance that
severe thunderstorms will accompany this frontal passage. This is
due to the combination of strong thermodynamic and dynamic forcing
coming together across the region. Thermodynamically...a Theta-E
ridge will be across the region...lifted indices will be
negative...and the lifted condensation levels should be around 950
mb. Thus...ample fuel should be in place to support convective
development. Dynamically...the strong 120 knot jet streak will
pass directly through the lower Mississippi Valley...with the
region in the favorable right entrance region of the jet after
midnight. In addition...a very strong low level jet of 55 knots
is expected to form over the area...resulting in speed shear of 35
to 40 knots from 0-3 km at 06z. Given the overall wind
profile...expect more a linear event to affect the region
tonight...with bowing segments producing some hail and strong
damaging winds.
Member Since: July 3, 2005 Posts: 424 Comments: 128284
77. CCTXangel
2:07 AM CDT on March 18, 2008
Anyone online right now? I'm looking at these amazing storms on Radar. Wondering what they are going to look like when they get towards Corpus Christi.

Anyone have any predictions?
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76. TampaSpin
2:17 AM EDT on March 18, 2008
A classic vortex on radar nearing Sonora Tx. They should be taking cover.....the hook is very visible on radar.
Member Since: September 2, 2007 Posts: 178 Comments: 20439
75. Dropsonde
12:26 AM EDT on March 18, 2008
Regarding the Atlanta tornado, here's what Roger Edwards has had to say about tornadoes hitting big venues:

Online Tornado FAQ
What about tornado safety in sports stadiums or outdoor festivals? Excellent question -- and a very, very disturbing one to many meteorologists. Tornadoes have passed close to such gatherings on a few occasions, including a horse race in Omaha on 6 May 1975 and a crowded dog track in West Memphis AR on 14 December 1987. A supercell without a tornado hit a riverside festival in Ft. Worth in 1995, catching over 10,000 people outdoors and bashing many of them with hail bigger than baseballs. Just in the last few years, tornadoes have hit the football stadium for the NFL Tennessee Titans, and the basketball arena for the NBA Utah Jazz. Fortunately, they were both nearly empty of people at the time. There is the potential for massive death tolls if a stadium or fairground is hit by a tornado during a concert, festival or sporting event -- even with a warning in effect. Fans may never know about the warning; and even if they do, mass-panic could ensue and result in casualties even if the tornado doesn't hit.

It looks like this was an incredibly close call. The tornado was 6 mph shy of EF-3, and it put holes in the stadium roof. Has anyone done studies on the type of winds that would be required to actually destroy a stadium and make it a hazard for the people in it? It's not one of the indicators in the EF Scale, but if 130 mph winds damaged the roof, it probably wouldn't require more than about 60-70 mph more to create a life-threatening situation, because of the extra debris that would be in those winds. I hope that this close call gets people's attention.
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74. TampaSpin
12:40 AM EDT on March 18, 2008
Its getting worse in Texas........long night ahead it appears.
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73. atmoaggie
4:30 AM GMT on March 18, 2008
And look at the sharp front defined in the IR:

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72. atmoaggie
4:27 AM GMT on March 18, 2008
Nice convergence zone (G'nite all):

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71. TampaSpin
12:22 AM EDT on March 18, 2008
Looks like Texas has its hands full.....
Member Since: September 2, 2007 Posts: 178 Comments: 20439
70. atmoaggie
4:18 AM GMT on March 18, 2008
For GFS data and RUC (really WRF now) I like UCAR Link
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69. TampaSpin
12:17 AM EDT on March 18, 2008
Sure looks like a problem
Member Since: September 2, 2007 Posts: 178 Comments: 20439
68. TampaSpin
12:16 AM EDT on March 18, 2008
BULLETIN - EAS ACTIVATION REQUESTED TORNADO WARNING NATIONAL WEATHER SERVICE SAN ANGELO TX 1116 PM CDT MON MAR 17 2008 THE NATIONAL WEATHER SERVICE IN SAN ANGELO HAS ISSUED A * TORNADO WARNING FOR... SOUTHEASTERN TOM GREEN COUNTY IN WEST CENTRAL TEXAS... CENTRAL SCHLEICHER COUNTY IN WEST CENTRAL TEXAS...
Member Since: September 2, 2007 Posts: 178 Comments: 20439
67. TampaSpin
12:16 AM EDT on March 18, 2008
Looks like a vortex nearing Robert Lee Texas.
Member Since: September 2, 2007 Posts: 178 Comments: 20439
65. stormhank
1:56 AM GMT on March 18, 2008
can someone give me a link to the computers model web site? gfdl cmc etc.. i just got new pc n lost all my shortcuts
Member Since: September 8, 2005 Posts: 0 Comments: 1386
64. franck
1:48 AM GMT on March 18, 2008
terra nova...fairly distinct hook echo on the right hand storm...and very large cell.
Member Since: August 30, 2005 Posts: 0 Comments: 1150
61. TerraNova
9:25 PM EDT on March 17, 2008
Good night all...tomorrow looks to also be active in weather (MODERATE risk).
Member Since: July 30, 2007 Posts: 76 Comments: 4063
60. TerraNova
9:23 PM EDT on March 17, 2008
The two big storms in South Texas have very strong vortex signatures with multiple rotations within them (the one to the left just gained a tornado warning after I took the image)...classic hook shapes...(from GRLevel3). Vortexes are in pink triangles, Severe storm warnings in red and tornado warnings in purple. The little swirls are MESO's.



Also there's a cluster of storms south of Abilene with tornado warnings for portions of Taylor, Nolan, and Runnels counties.
Member Since: July 30, 2007 Posts: 76 Comments: 4063
57. Weather456
8:53 PM AST on March 17, 2008
lol
Member Since: July 24, 2005 Posts: 407 Comments: 19076
56. robomaeyhem
8:32 PM EDT on March 17, 2008



Guys, on the 12th, we will see Dr. Jeff Masters on the moon, and this picture proves it!
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55. 1900hurricane
12:32 AM GMT on March 18, 2008
Some good information on the current outbreak can be found here
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53. Weather456
7:11 PM AST on March 17, 2008
MODIS detects low level jet off the coast of Southern Africa.

Over the weekend I posted some information on the coastal jet of Southern Africa. In the MODIS TERRA image below taken today, the hydraulic theory is illustrated.

This thoery simply states as air flowing along a coast passes a cape it expands and moves offshore forming what is called an expansion fan.

Member Since: July 24, 2005 Posts: 407 Comments: 19076
52. TerraNova
7:38 PM EDT on March 17, 2008
These storms have just exploded in the past hour. Note the southern most storm in the image...the radar i'm looking at is hinting at a possible mesocyclone along with hail bigger than an inch. Right now we have about 6 severe storm warnings and one tornado warning. I think the mets in Texas and OK have their work cut out for them tonight.

Member Since: July 30, 2007 Posts: 76 Comments: 4063
47. dean2007
10:58 PM GMT on March 17, 2008
Dr. Masters, I remember a post you had done on the Microburst of December 9th 2005 showing a satellite image of the eye that had passed over Cape Cod, MA. I was wondering If you have any more information that I can use, or maybe any archives from your post that is not there anymore? Thanks.
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45. TerraNova
6:29 PM EDT on March 17, 2008
Two cells have just begun to develop north of Ballinger TX/South of Abilene. To me they look to be forming rather quickly. The maximum dBZ on the radar has jumped from 47 on the previous scan of the biggest to 57 on the next.

Member Since: July 30, 2007 Posts: 76 Comments: 4063
42. odog1999
10:14 PM GMT on March 17, 2008
Another excerpt (emphasis theirs) from slide 8:
"The second fatality occurred at the Shields Boulevard overpass at its junction with Interstate 35 in the City of Moore. These photographs show many of the same things as the pictures of the 16th Street overpass. The top two photographs were taken by the author in late September. On the upper right is a view, looking south, of the west side of the bridge where the people were huddled. In the drainage ditch in the foreground, is a small memorial to the lady killed at this location. Her body was not found until one week after the tornado. The spot where her body was eventually found was buried underneath 6 to 8 feet of debris immediately after the tornado passed."
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41. odog1999
10:11 PM GMT on March 17, 2008
9. BigTuna 3:10 PM GMT on March 17, 2008
some time ago I heard that the Moore F5 realized the fears that many in the meteorological community had after the circa-1991 video aired of people taking refuge under a bridge overpass. Apparently several people did exactly that and were sucked out and killed just as predicted.

Powerpoint slides discussing hiding below an underpass:
http://www.srh.noaa.gov/oun/papers/overpass.html

From slide 6:
"It is our contention that highway overpasses are inadequate tornado sheltering locations for the following meteorological reasons. First, ALL tornadoes have some amount of debris within their near-surface flow. In the case of a strong or violent tornado, much more debris would be present, traveling at much higher speeds, especially when debris from man-made structures is involved. In strong and violent tornadoes, typically harmless everyday items such as shingles, boards, pop cans, dishes (or pieces thereof) become dangerous missiles and are responsible for most tornado casualties. Second, by climbing up under an overpass, people will be exposed to higher wind speeds and more flying debris. Third, the narrow passage underneath an overpass might cause an increase in the wind speed under the bridge. The extent to which this is true, and the circumstances under which it could happen are not known, but this is at least a possibility. Fourth, most overpasses don't have girders or support beams for handholds or small ledges into which to crawl. And, finally, if an overpass is directly in the path of a tornado, the wind will change direction nearly 180 degrees as the vortex passes. Thus, if one side of the overpass was protected from the highest wind speeds as the tornado approached, that same side of the bridge will be completely exposed to the wind and flying debris as the tornado moves away and vice-versa.

Seeking shelter under a highway overpass is to become a stationary target for flying debris, with a substantial risk of being blown out and carried by the tornado winds. Safety in such a location is merely an illusion."
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40. Patrap
4:53 PM CDT on March 17, 2008

Grand Etang, Nova Scotia
wunderground page Link



Local Time: 6:53 PM ADT Your time: 4:53 PM CDT — Set My Timezone Lat/Lon: 46.5° N 61.0° W (Google Map)
Current Conditions

Grand Etang, CA (Airport)
Updated: 53 min 16 sec ago
Unknown
27 °F / -3 °C
N/A
Windchill: 8 °F / -13 °C
Humidity: 69%
Dew Point: 18 °F / -8 °C
Wind: 40 mph / 65 km/h / 18.0 m/s from the North
Wind Gust: 51 mph / 82 km/h / 22.6 m/s
Member Since: July 3, 2005 Posts: 424 Comments: 128284
39. Patrap
4:49 PM CDT on March 17, 2008
Environment Canada's Official Weather Warnings

Warnings
Halifax County - east of Porters Lake
3:41 PM ADT Monday 17 March 2008
Wind warning for
Halifax County - east of Porters Lake continued

Wind gusts to near 90 km/h will continue tonight and into Tuesday morning.

This is a warning that potentially damaging winds are occurring in these regions. Monitor weather conditions..Listen for updated statements.



A very intense low well to the southeast of Nova Scotia will remain nearly stationary tonight then weaken gradually on Tuesday as it drifts eastward. Strong northerly winds well away from the low are affecting Nova Scotia and will continue into the day Tuesday. Gusts up to 90 km/h are forecast over the eastern part of the province.

Member Since: July 3, 2005 Posts: 424 Comments: 128284
38. Michfan
9:50 PM GMT on March 17, 2008
ATLANTA -- The storms that hit metro Atlanta were even worse than most people thought.

There were four and possibly as many 14 tornadoes spawned over the weekend, officials at the National Weather Service said Monday afternoon.


Link
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37. Weather456
5:42 PM AST on March 17, 2008
CENTRAL AMERICA AND THE CARIBBEAN REGION....

Upper ridging and dry air dominates the Caribbean basin, thereby, deep convection remains absent. The high pressure system along the Eastern United States will maintain a light to moderate easterly flow over the Caribbean as seen on visible imagery. Some patches of low level moisture will move across the Lesser Antilles at times, causing a passing light to moderate shower or two. Seas will be 4-5 ft mainly east of 70W, increasing to 6 ft west of 70W. The highest swells are expected to be 8-11 ft along the Colombian Coast and SW Caribbean.

by W456
Member Since: July 24, 2005 Posts: 407 Comments: 19076
36. Patrap
4:47 PM CDT on March 17, 2008
Goes-12 Imagery of thew Atlantic Low CWS Link
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35. Michfan
9:45 PM GMT on March 17, 2008
This is when i wish those new budgets kicked in for the Hurricane Hunters to go into extratropical storms such as this.
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34. Weather456
5:39 PM AST on March 17, 2008
29. Michfan 4:30 PM AST on March 17, 2008
Wow that is an amazing picture. Whats the pressure on that?


Analysed 966 mb

Lowest reported pressure 987 mb
Member Since: July 24, 2005 Posts: 407 Comments: 19076
33. Weather456
4:25 PM AST on March 17, 2008
....SYNOPSIS....

GULF OF MEXICO/NORTHWEST ATLANTIC OCEAN WEST OF 50W....

A deep layer ridge has its axis extending from the Western Caribbean, across the Gulf into the Eastern half of the United States. Mid-upper dry air covers most of the Gulf with the most prevalent amounts across the Southeastern corner; while diffluent flow around the crest of the ridge is enhancing widespread cloudiness and showers along a serious of surface fronts/lows over the Southern United States. Visible satellite imagery showed a dissipating frontal boundary extending from the Atlantic, through the Florida Straits...along the length of the Western Cuba Coast...and over the Eastern Gulf to the Mississippi Coast before finally connecting to a series of fronts over the Southern United States. The front lies within the dry environment under the ridge and thus only scattered low clouds are within 60 nmi of the front.

QuikSCAT and marine observations indicated that a strong transitory anticyclone along the Eastern United States is supporting 10-20 knot anticyclonic flow over the Gulf of Mexico with the strongest winds approaching the coast of Northern Mexico, Texas and Louisiana where the pressure gradient is clearly tightest. Swells will be mainly easterly at around 5-6 ft everywhere, approaching 7-8 ft over the Gulf west of 90W. Swells should be less significant along the West Coast of the Florida Peninsula where the flow is mainly offshore.

A large vertically stacked low pressure area is located at 40.9N/56.6W. This system is supporting a well define cold front which extends from 33N/50W arching towards the Southern Bahamas, then along the length of Cuba and into the Southeast Gulf of Mexico. Scattered showers are within 150 nmi of the leading frontal rope structures. Now, a very strong high pressure system...1038 mb...over the Eastern United States and Canada is producing moderate to very strong northwest winds over much of the area behind the cold front from 80W to 50W. This continues to produce fairly large northwest wind waves and swells across the area...especially north of 25N. Buoy 41038, located near 31.9784 N 69.649 W, reported a peak wind gust of 49 knots around 1200 UTC today and peak swells of 19 ft which are still being reported. Other marine reports indicated some gale force winds reaching the Bahaman Islands.

by W456
Member Since: July 24, 2005 Posts: 407 Comments: 19076
32. HadesGodWyvern (Mod)
9:31 PM GMT on March 17, 2008
Whats the pressure on that?

---
not really sure looks like the analyse charts are suggesting 968 MB
Member Since: May 24, 2006 Posts: 50 Comments: 45302

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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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