Gulf of Mexico disturbance 93L a Lousiana flood threat; Katia a hurricane

By: Dr. Jeff Masters , 3:28 PM GMT on September 01, 2011

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Surface winds over the northern Gulf of Mexico are rising, pressures are falling, and heavy thunderstorms are building today thanks to a tropical disturbance (Invest 93L) that is the product of a tropical wave interacting with an upper-level low pressure system. At 8:35 am CDT, winds at the Mississippi Canyon 711 oil rig were south-southeast at 38 mph. This is just 1 mph below tropical storm force, but the wind instrument was 348 feet (106 m) above the ocean surface, and winds near the surface were probably considerably lower, near 30 mph. Long range radar out of Mobile, Alabama shows heavy rain showers building along the northern Gulf Coast, but these rain showers are not organized into spiral bands and show no signs of rotation. Strong upper-level winds out of the west-northwest are creating 30 knots of wind shear over 93L, keeping the storm's heavy thunderstorms disorganized. Strong onshore winds raising tides to 1 - 2 feet above normal are likely along the northern Gulf Coast through the weekend, and coastal flood statements have been issued for the region.


Figure 1. Predicted rainfall for the 5-day period ending at 8am EDT Sep 6, 2011. A large region of rains in excess of 15 inches is expected over Southeast Louisiana. Image credit: NOAA/HPC.


Figure 2. U.S. drought conditions on August 30. The rains from 93L have the potential to bring major drought relief to drought-stricken portions of the coast. Image Credit: U.S. Drought Monitor.

By late tonight, wind shear is expected to drop to the moderate range, below 20 knots, and 93L should begin to organize into a tropical depression. Wind shear is expected to remain moderate, 10 - 20 knots, into Monday. There is some cold, dry air aloft that will retard this process, and I think the earliest we would see a tropical depression is Friday afternoon. NHC is giving 93L a 70% chance of developing into a tropical depression by Saturday morning. All of the major models develop 93L near the Louisiana coast, and show a slow and erratic movement due to weak steering currents. Coastal Louisiana, Mississippi, Alabama, and the extreme western Panhandle of Florida will likely receive very heavy flooding rains beginning this afternoon and intensifying Friday and Saturday. The latest rainfall forecast from NOAA Hydrological Prediction Center (Figure 1) shows that a large area of 15+ inches of rain is expected over Southeast Louisiana. The region is under moderate drought, so flooding problems will be delayed compared to what we'd normally expect from heavy rains of over a foot. Nevertheless, minor to moderate freshwater flooding is likely from 93L, and flash flood watches are posted for New Orleans and surrounding areas, and rainfall amounts of 1 - 3 inches per hour are possible in some of the heavier rain squalls. Ocean temperatures are near record warmth, 88°F (31.3°C), which will provide plenty of moisture for heavy rains, and plenty of energy to help 93L strengthen into a tropical storm. Most of the models predict 93L will have some motion to the west by Saturday, which would bring rains to the Texas coast near the Louisiana border. Steering currents will be weak in the Gulf this weekend and early next week, making it difficult to predict where the storm might go. If 93L stays over water through Tuesday, like the ECMWF model is predicting, the storm would be a threat to intensify into a hurricane. Most of the other models predict 93L will move ashore over Louisiana by Sunday, limiting the storm's development to just tropical storm strength. I think it at least 50% likely 93L will be a tropical storm with 40 - 60 mph winds along the coast of Louisiana by Sunday.

Hurricane Katia
Hurricane Katia intensified into the 2nd hurricane of the 2011 season last night, and continues its long trek across the Atlantic Ocean today. Katia is expected to arrive at a position several hundred miles north of the Northern Lesser Antilles Islands by Monday. The islands are not in the cone of uncertainty, and it appears unlikely that they will receive tropical storm-force winds from Katia. Satellite images show that Katia is a well-organized storm with plenty of heavy thunderstorms, but the storm has been struggling with dry air and moderate wind shear of 10 -20 knots, and is looking less organized than it did last night. These problems will likely diminish by Friday night, as the upper low bringing the wind shear moves away. It is still unclear how much of a threat Katia may post to the U.S. Dr. Bob Hart's Historical Tropical Cyclone Probability web page suggests shows that tropical storms in Katia's current position have an 16% chance of hitting North Carolina, a 21% chance of hitting Canada, a 12% chance of hitting Florida, and a 54% chance of never hitting land. I suspect that Katia will turn north before reaching the U.S. and potentially threaten Bermuda and Canada, based on what past storms in similar situations have done, and assuming the jet stream maintains its current pattern of bringing frequent troughs of low pressure off the coast of the U.S. It will be another day or two before the models will begin to have a handle on the long-term fate of Katia, though.


Figure 3. Morning satellite image of Katia.

94L
A well-organized low pressure system with a surface circulation and limited heavy thunderstorm activity has developed between Bermuda and the Canadian Maritimes. This disturbance, (94L), is headed out to sea, and is being given a 10% chance of developing into a tropical depression by NHC. 94L is under a very high 30 - 40 knots of wind shear, and will not be able to intensify very much. However, Tropical Storm Jose formed from a similar type of system, and we might get surprised by 94L.

I'll have more on Irene in tomorrow's post.

Jeff Masters

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Quoting Neapolitan:

The 2011 drought is by far the worst single-year one in Texas--far worse, that is, than any that occurred during the 1950s (or any other period). The current drought is affecting a wider area, and it's been more profound, with much hotter temperatures, less precipitation, and drier soil. Of course, the 1950s multi-year drought lasted longer; it remains to be seen whether the current will continue long enough to surpass the old one(s). FWIW, Texas State Climatologist Dr. Nielsen-Gammon says that that Texas is "likely to be" at the start of a multiyear drought.


If this is the case parts of it could become uninhabitable at this rate... No water to drink. No water to put out fires. Widespread deforestation/defoliation. Massive number of houses and buildings destroyed by the subsidence of expansive clay soils under their foundations.

At some point many of us would have to just abandon everything and leave.
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Well, they declared Irene with a very weak and broad center of circulation, so why not 93L?
Member Since: July 6, 2010 Posts: 113 Comments: 32531
I don't really think we'll see an upgrade of 93L yet. Maybe later tonight.
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Quoting TropicalAnalystwx13:


But the flight level is lower than the surface level...
I *think* that is going to be expected with this system for a while, yet. This is an odd one where the mid-level circulation isn't as developed as the surface circulation. Even the 5 knot flight level west wind had a 22 knot surface wind.

So far, all of the stronger areas of surface winds have been under a slower flight level wind.

This system is vorticity inverted...
Member Since: August 16, 2007 Posts: 6 Comments: 12463
Quoting trHUrrIXC5MMX:


yeah why not... another $32 billion and 100 lives... oil rigs closed bombing oil price to $4.30g
NOT strength wise... track wise.
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Quoting Sfloridacat5:


Was Ike the system that was first forecast to turn and go East of Florida, but the forecast cone kept moving Westward over time?

More or less.  Ike largely followed the left edge of his cone.  The turn to the SW was forecast, but it went on longer than expected, so instead of turning back WNW to NW and heading toward the east coast of Florida, it kept getting delayed until he was at Cuba.

I've never done a rigorous analysis, but I am reasonably sure he was always within the three day cone, but spent several days on the left edge.
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1010 mb Low now in 93L,

Click on fronts..


Floater - Rainbow Color Infrared Loop
Member Since: July 3, 2005 Posts: 426 Comments: 129093



Quoting MiamiHurricanes09:
Nothing to get worried about, but the recent westward motion is pretty interesting.
 
For those keeping track at home.... per Dr Masters...
 
 

8/30/11  19% chance of hitting North Carolina, a 16% chance of hitting Canada, an 11% chance of hitting Florida, and a 47% chance of never hitting land.
8/31/11  11% chance of hitting North Carolina, a 12% chance of hitting Canada, a 5% chance of hitting Florida, and a 62% chance of never hitting land
9/1/11  16% chance of hitting North Carolina, a 21% chance of hitting Canada, a 12% chance of hitting Florida, and a 54% chance of never hitting land.
I really enjoy it when he breaks down like that... lets me know  when to start worrying.  I suspect if the NW turn projected to start tommorrow morning does occur and points are south of 18 N and/or very west of 53.4W by tommorrow night  we could start a little worry then...
 
Member Since: August 25, 2006 Posts: 0 Comments: 65
Quoting TropicalAnalystwx13:
Good afternoon guys...Just got home from school and decided to switch to the weather channel for a second. They said that recon found west winds...?


I dunno, that's what I've been hearing...albeit very weak west winds, probably not worthy of an upgrade.

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Quoting IKE:
6-10 day precip...


And one must question why they call Florida the sunshine state in times like this...
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Quoting angiest:

You are thinking Ivan.


Yes... I stand corrected...
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Quoting TropicalAnalystwx13:
Good afternoon guys...Just got home from school and decided to switch to the weather channel for a second. They said that recon found west winds...?


yeah




Very broad and weak area of low pressure, however, so the circulation is also very weak and broad.
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Quoting WandoMarsh:


Thats funny... because that isn't the entirety of Ike's path... he went back out into the Atlantic and pulled a u-turn and came back west, crossed Florida and hit Texas again... much weaker, but still the same system.
um, are you talking about Ivan? I don't remember if Ike did the same thing...
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Quoting IKE:
6-10 day precip...




We've seen very little sun over the past week or so in my area of S.W. Florida. Today was another cloudy day. Went out on the beach (Naples Fl.)a little earlier today and there were only 5 people and 1 dog.
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Quoting redwagon:

I dunno, ask Dallas what they did. They're the only ones not in exceptional drought.

I still stand by my hope we'll get a Hermine II before too much longer. Everything is set up for it, just need an EPAC pop-up that suddenly feels a poleward urge.


We've occasionally gotten the lower edge of systems moving through Oklahoma, several this spring and then a bit under an inch in August. So we're a little better off water-wise here but this heat is effin' relentless.
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I think it was fairly obvious that Katia wasn't going to develop all that quickly without any bumps in her road. It was also somewhat obvious that she would likely take a more westerly track. I think the NHC was depending on Katia going through rapid intensification over the past 12 to 18 hours, which would have made it less likely that she'd be drastically effected by sheer.

The next couple of days will be pretty rough for Katia, but I see a better environment for her development for days 3 to 7. After that it all depends on the incoming trough coming through the eastern US, however I am a little skeptical about that trough. There is indications of strong ridging developing over the southeast US east of whatever 93L becomes (or doesn't become). Models already depict the trough becoming slower and slightly weaker as each run comes in, so I have a feeling we're going to end up with another situation similar to Irene... in terms of possibilities. It likely won't take the same exact track, maybe it will miss the coast all together still... but I certainly would not be saying Katia is a low threat to the U.S. Coastline by any means. More like a moderate threat.

Katia needs to get her act together quite a bit more, and quickly, in order to be picked up by any mid-latitude troughs before she approached the U.S.
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879. 996tt
Quoting jascott1967:


It hasn't been this dry here since 1933 and August was the hottest in Texas since they kept records. The situation in Texas is a lot worse than the nation thinks it is but it will eventually start hitting the pocket books of many. Cattle owners are having to sell off their breeding stock at cheap prices because they can't feed them due to lack of good hay crops. At first, the price of meat will be cheaper but eventually it will really start to sky rocket because the supply won't be there.

The drought in Texas has already reached 5 billion dollars and it's only going to get worse...maybe much worse. And the general public across the nation is oblivious to just how bad it is but they'll find out soon. Cotton products will be higher, along with beef and poultry. Get ready!


Doubt it. Monetary policies QE XXX and inflation when calcated under real and prior formulas is more of a factor. Droughts suck, but beef, poultry and especially cotton comes from places other than Texas and demand will be met. Flood and tornado devastation was pretty bad this year also. Lots of people hurting. Perhaps the hurricane Gods will be afraid of rising beef cost and cast a Cat 5 in your direction.
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Quoting MiamiHurricanes09:
No renumbers...


Yet.

They may declare it at 5PM, but I think 11PM or 5AM is more likely. Always could have a Special Advisory too...
Member Since: July 6, 2010 Posts: 113 Comments: 32531
Extended Forecast Discussion

Excerpt:

FINAL PROGS ARE STAYING WITH THE SAME BLEND USED IN THE UPDATED
PRELIM...SAVE ONE IMPORTANT DIFFERENCE: A NW ADJUSTMENT TO THE
TRACK OF AN INCIPIENT TROPICAL SYS IN THE WRN GULF OF MEXICO. 12Z
MODELS SUPPORTED THIS NWD ADJUSTMENT BY THE NHC...WITH MUCH BETTER
CONSENSUS THAN IN THE 00Z/01 MODEL RUNS. STAY TUNES TO OUTLOOKS
FROM THE NATIONAL HURRICANE CENTER.



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Quoting katadman:



A cat of nine tails lashing the east coast! lol
Cat of nine? I'm sure that the hurricane scale only goes up to 5.
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Quoting atmoaggie:
Umm, probably has been posted by now, but a while ago:

Time: 19:07:30Z
Coordinates: 26.05N 89.0833W
Acft. Static Air Press: 959.5 mb (~ 28.33 inHg)
Acft. Geopotential Hgt: 459 meters (~ 1,506 feet)
Extrap. Sfc. Press: 1010.8 mb (~ 29.85 inHg)
D-value: -
Flt. Lvl. Wind (30s): From 179° at 33 knots (From the S at ~ 37.9 mph)
Air Temp: 23.3°C (~ 73.9°F)
Dew Pt: 22.9°C (~ 73.2°F)
Peak (10s) Flt. Lvl. Wind: 34 knots (~ 39.1 mph)
SFMR Peak (10s) Sfc. Wind: 44 knots (~ 50.6 mph)
SFMR Rain Rate: 7 mm/hr (~ 0.28 in/hr)
(*) Denotes suspect data


But the flight level is lower than the surface level...
Member Since: July 6, 2010 Posts: 113 Comments: 32531
873. IKE
6-10 day precip...


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No renumbers...
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Quoting WandoMarsh:


Thats funny... because that isn't the entirety of Ike's path... he went back out into the Atlantic and pulled a u-turn and came back west, crossed Florida and hit Texas again... much weaker, but still the same system.


Was Ike the system that was first forecast to turn and go East of Florida, but the forecast cone kept moving Westward over time?
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Quoting katadman:


Thanks. It even happens with different browsers. Not sure what's going on.


I was having the same issues. I upgraded to IE 9 yesterday and haven't had it yet. It wasn't consistent when I was having issues. One day fine and the next it was as you described.
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Umm, probably has been posted by now, but a while ago:

Time: 19:07:30Z
Coordinates: 26.05N 89.0833W
Acft. Static Air Press: 959.5 mb (~ 28.33 inHg)
Acft. Geopotential Hgt: 459 meters (~ 1,506 feet)
Extrap. Sfc. Press: 1010.8 mb (~ 29.85 inHg)
D-value: -
Flt. Lvl. Wind (30s): From 179° at 33 knots (From the S at ~ 37.9 mph)
Air Temp: 23.3°C (~ 73.9°F)
Dew Pt: 22.9°C (~ 73.2°F)
Peak (10s) Flt. Lvl. Wind: 34 knots (~ 39.1 mph)
SFMR Peak (10s) Sfc. Wind: 44 knots (~ 50.6 mph)
SFMR Rain Rate: 7 mm/hr (~ 0.28 in/hr)
(*) Denotes suspect data
Member Since: August 16, 2007 Posts: 6 Comments: 12463

Quoting WandoMarsh:


Thats funny... because that isn't the entirety of Ike's path... he went back out into the Atlantic and pulled a u-turn and came back west, crossed Florida and hit Texas again... much weaker, but still the same system.
You are thinking Ivan.
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Good afternoon guys...Just got home from school and decided to switch to the weather channel for a second. They said that recon found west winds...?
Member Since: July 6, 2010 Posts: 113 Comments: 32531
Quoting Bluestorm5:
Maybe Katia might pull off Ike?



yeah why not... another $32 billion and 100 lives... oil rigs closed bombing oil price to $4.30g
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Quoting Bluestorm5:
Maybe Katia might pull off Ike?



Thats funny... because that isn't the entirety of Ike's path... he went back out into the Atlantic and pulled a u-turn and came back west, crossed Florida and hit Texas again... much weaker, but still the same system.
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Quoting TomTaylor:

Yes indeed...12z vs 18z:




A cat of nine tails lashing the east coast! lol
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Quoting CloudGatherer:
From SAB:

DATE/TIME LAT LON CLASSIFICATION STORM
01/1745 UTC 15.8N 48.5W T3.5/4.0 KATIA -- Atlantic
01/1745 UTC 26.6N 90.8W TOO WEAK 93L -- Atlantic
01/1745 UTC 37.2N 64.0W T1.5/1.5 94L -- Atlantic

The 94L number really ought to justify a Tropical Depression at 5pm. And the ambiguous result for Katia will probably keep it as a hurricane in the next advisory; they're really loath to downgrade until it's crystal clear that it's necessary, particularly when they'd just have to reupgrade again.


It wouldn't be a TD. If it gets organized it should go straight to TS since they already know it has TS strength winds.

"TROPICAL WEATHER OUTLOOK
NWS NATIONAL HURRICANE CENTER MIAMI FL
200 PM EDT THU SEP 1 2011
2. A LOW PRESSURE SYSTEM LOCATED ABOUT 360 MILES NORTH OF BERMUDA HAS
CHANGED LITTLE OVER THE PAST FEW HOURS. THIS SYSTEM IS PRODUCING
WINDS OF TROPICAL STORM FORCE...AND ONLY A SLIGHT INCREASE IN
ORGANIZATION COULD RESULT IN THE FORMATION OF A TROPICAL STORM.
THE LOW IS MOVING LITTLE AT THIS TIME...BUT SHOULD BEGIN TO MOVE
NORTHEASTWARD AT 10 TO 15 MPH TONIGHT. THIS SYSTEM HAS A MEDIUM
CHANCE...50 PERCENT...OF BECOMING A TROPICAL CYCLONE DURING THE
NEXT 48 HOURS.
"
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Seems odd that there is no afternoon update to the Houston forecast discussion yet.
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859. drj27
Looks like fl panhandle will dodge this one in the gulf
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Quoting trHUrrIXC5MMX:

wait!, you will get your big slice soon


you know something we don't....
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Quoting gulfscout:
I would rather get the rain to Texas without a hurricane thanks.
That's OK, looking more and more like a total miss. ;(
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Quoting SWLACajun:


Kind of looks like a doctor's signature huh?


HA! Yea, like my dad's..now mine a bit. Probably going to check generator when I get home, but I think this will mainly be a little rainfest..altho one or two call for cat 1.
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Thanks!


Quoting Levi32:


Again it reflects the danger of the pattern with a tendency for ridging north of Katia's area over southeast Canada. I still think she'll pass between Cape Hatteras and Bermuda, but one must always be wary of a Dora-type track in such patterns. I think it's unlikely here, but folks should still watch the storm and not forget about it.
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ive noticed the models take lee into lousiana but dont make a loop like they did before kinda disagree with that im thinking lee will move NW then sw then south then east north east then north east.
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Quoting KeysieLife:
It's usually due to an image that was posted. What version of IE are you using? Since upgrading to 9 the issue seems to have resolved itself. Also, you can try changing the comments viewed from say 100 to 50 so the image will rotate out faster.

Hope that helps!


Thanks. It even happens with different browsers. Not sure what's going on.
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Quoting neonlazer:


Looks like models are finally not quite as spagetti, my friend already has a hurricane party planned..yea..we live in lafayette..right in the middle of the jumble!


Kind of looks like a doctor's signature huh?
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Quoting portcharlotte:
Levi

A big shift west with the European model for Katia...your thoughts



Again it reflects the danger of the pattern with a tendency for ridging north of Katia's area over southeast Canada. I still think she'll pass between Cape Hatteras and Bermuda, but one must always be wary of a Dora-type track in such patterns. I think it's unlikely here, but folks should still watch the storm and not forget about it.
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From SAB:

DATE/TIME LAT LON CLASSIFICATION STORM
01/1745 UTC 15.8N 48.5W T3.5/4.0 KATIA -- Atlantic
01/1745 UTC 26.6N 90.8W TOO WEAK 93L -- Atlantic
01/1745 UTC 37.2N 64.0W T1.5/1.5 94L -- Atlantic

The 94L number really ought to justify a Tropical Depression at 5pm. And the ambiguous result for Katia will probably keep it as a hurricane in the next advisory; they're really loath to downgrade until it's crystal clear that it's necessary, particularly when they'd just have to reupgrade again.
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Quoting StormFreakyisher:
As we speak, Katia is plunging West at 18mph and as it continues to do so, the models will keep shifting west. This is getting me worried...
Nothing to get worried about, but the recent westward motion is pretty interesting.
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Quoting Levi32:
I should also really point out a big slip in terminology that is working its way into the blog. I am guilty of it as well sometimes in my videos. We can't say that a "recurving storm" means one that is missing land. That is entirely incorrect. In fact, the majority of storms that hit North America ARE recurving. The question should be whether the storm will hit land as it recurves, not whether it will recurve. Most storms do recurve into the mid-latitudes, and that can occur over the ocean or over land.

True. Recurvature doesn't and shouldn't necessarily imply that no land will be affected. In fact, if it weren't for recurving storms, we here on the west coast of Florida wouldn't see nearly so many strikes.
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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.