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 Tazmanian:
am not sure if any one say this but this is not good


2380. mrpuertorico 6:45 PM PDT on September 01, 2011 0 Hide this comment.
AFTER KATIA CLEARS THE AREA EARLY NEXT WEEK...MODELS SHOW A
SIGNIFICANT CHANGE TO THE UPPER LEVEL PATTERN WITH TUTTS/TROUGH
THAT ARE CURRENTLY PRESENT ACROSS THE ATLC TO BE REPLACED BY A
STRONG RIDGE ALOFT. THIS WILL BLOCK ANY POTENTIAL TROPICAL
CYCLONES ORIGINATING IN THE TROPICAL ATLC FROM TAKING THE NORTHERN
ROUTE. WHILE WE ARE MORE THAN LIKELY TO DODGE THE BULLET WITH
KATIA THIS MAY NOT BE THE CASE FOR FUTURE STORMS IN THE NEXT 7-14
DAYS.
How many times have they said that and it has failed to materialize, I'll give it a 50 % chance of it actually happening, since I'm a believer in change.
Member Since: August 31, 2009 Posts: 0 Comments: 5628
KATIA IS ROARING...all we need now is an eyewall...
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LAnovice: " Don't care if that is called an "invest" or a TD"

Agreed. When they can snatch the peble from NHS's hand...

Good night, all.
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Quoting FLdewey:


Clearly you've never been to San Diego.

If the official track holds true for "TD 13" Texas will not receive much rain... how cruel.


Yeah, it's kind of annoying. 2.5 inches at best looks like.
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000
WTNT42 KNHC 020237
TCDAT2

TROPICAL STORM KATIA DISCUSSION NUMBER 16
NWS NATIONAL HURRICANE CENTER MIAMI FL AL122011
1100 PM AST THU SEP 01 2011

MICROWAVE IMAGES AROUND 2245 UTC SHOWED THE CENTER OF KATIA ON THE
EDGE OF THE DEEP CONVECTION...BUT MORE RECENT SATELLITE IMAGES SHOW
AN INCREASE OF THE THUNDERSTORM ACTIVITY AND IT APPEARS THAT THE
CENTER IS AGAIN UNDER THE CANOPY. THE OUTFLOW HAS ALSO BECOME A
LITTLE BETTER DEFINED IN THE NORTHWEST QUADRANT. DVORAK T-NUMBERS
ONLY SUPPORT 55 KNOTS BUT GIVEN THAT THE CLOUD PATTERN IS A LITTLE
BETTER ORGANIZED THAN EARLIER THIS EVENING...THE INITIAL INTENSITY
IS KEPT AT 60 KNOTS. WATER VAPOR IMAGES STILL SHOW A SHARP
UPPER-TROUGH WITH ITS AXIS ALONG 56 DEGREES WEST LONGITUDE INDUCING
STRONG SOUTHWESTERLY SHEAR OVER KATIA. GLOBAL MODELS...MAINLY THE
GFS AND EVENTUALLY THE ECMWF INSIST ON WEAKENING THIS TROUGH AND
FORECAST A MORE FAVORABLE ENVIRONMENT FOR INTENSIFICATION IN A DAY
OR SO. THERE ARE NO SIGNS THAT THE TROUGH IS WEAKENING YET...AND
GIVEN THE CURRENT SHEAR...NO CHANGE IN STRENGTH IS INDICATED IN THE
NEXT 12 TO 18 HOURS. KATIA SHOULD BEGIN TO RE-INTENSIFY IN ABOUT 24
TO 36 HOURS AND BECOME A MAJOR HURRICANE IN A FEW DAYS ASSUMING
THAT THE ENVIRONMENT BECOMES LESS HOSTILE AS INDICATED BY GLOBAL
MODELS.

KATIA HAS SLOWED DOWN A LITTLE BIT AND IT APPEARS TO BE MOVING
TOWARD THE WEST-NORTHWEST OR 290 DEGREES AT 14 KNOTS AROUND THE
PERIPHERY OF THE SUBTROPICAL RIDGE. A TROUGH CURRENTLY LOCATED OVER
THE WESTERN ATLANTIC IS ERODING THE WESTERN SIDE OF THE SUBTROPICAL
RIDGE AND THIS WILL INDUCE A NORTHWESTERLY MOTION DURING THE NEXT
TWO TO THREE DAYS. HOWEVER...IN THE LONG RANGE...A STRONG MID-LEVEL
TROUGH IS FORECAST TO DEVELOP OVER THE GULF OF MEXICO AS THE
ATLANTIC SUBTROPICAL RIDGE BUILDS WESTWARD. THIS PATTERN SHOULD
FORCE KATIA ON A MORE WEST-NORTHWESTWARD MOTION BY THE END OF THE
FORECAST PERIOD AS INDICATED BY THE ECMWF AND THE GFS. THIS SMALL
BEND TO THE WEST-NORTHWEST IS REFLECTED IN THE OFFICIAL FORECAST.

ON THE FORECAST TRACK...KATIA WILL CONTINUE TO MOVE OVER OPEN WATER
DURING THE NEXT FIVE DAYS.


FORECAST POSITIONS AND MAX WINDS

INIT 02/0300Z 16.7N 50.6W 60 KT 70 MPH
12H 02/1200Z 17.5N 52.5W 60 KT 70 MPH
24H 03/0000Z 18.5N 54.0W 65 KT 75 MPH
36H 03/1200Z 19.5N 55.5W 75 KT 85 MPH
48H 04/0000Z 20.5N 57.0W 85 KT 100 MPH
72H 05/0000Z 22.5N 60.0W 95 KT 110 MPH
96H 06/0000Z 25.0N 63.5W 100 KT 115 MPH
120H 07/0000Z 26.5N 67.0W 105 KT 120 MPH

$$
FORECASTER AVILA
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Katia is looking better, firing some very deep convection.

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Does that new wave after Kathia has been named an invest yet? Does any model develop it? GFS ignores it... Two huge waves into Africa...

Member Since: August 2, 2010 Posts: 21 Comments: 9656
Quoting TampaSpin:


The gfs is still showing a loop? This map looks like my son and his friends used it for target practice with thier paintball guns. Go WEST!
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2634. Dennis8
Quoting TropicalAnalystwx13:
This is why people can't have civilized discussions...People get carried away with their opinions (almost guilty, lol) and start calling people names and telling to shut up (*cough Dennis8 *cough).


I never told anyone to shut up...cough cough..BUT ignore is the mature way and missiwx was on ignore moons ago as his input is pure fantasy
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I'm calm. I think the people I've been debating with have been calm. There is a difference between debating and arguing. We can have a debate on classification of a current system. It's on topic since the system is after all current, right? What else are we going to do? Sit here and post the same maps and information over and over? The reliable 00z models don't come out until an hour from now. Gotta do something to pass the time...
Member Since: July 15, 2006 Posts: 17 Comments: 10156
Using wind speed and a COC to determine the effects of a storm has been debated in the past few years/maybe decades. The NOAA/NHC is charged with a larger picture - IMHO - the NHC purpose is to alert citizens about damaging weather and the effect such weather will have on the populace it is charge to protect.
So - within that line of thinking - perhaps it is the rule book that needs to be changed. A storm can have great damaging effects - without the wind or a defined COC that a named storm or depression would require. Rain and tidal flooding are aspects of a tropical storm that are not included in the "rule book" for naming storms.
Me - I am happy to be told that there is something out there that warrants my actions - to prepare to shelter in place or move to higher ground. Don't care if that is called an "invest" or a TD. Unfortunately without a name or other designation - many people would not take a storm seriously.
Perhaps we need to look at changing the yardstick by which tropical systems and their damage is measured...
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Quoting Skyepony:
But the question is would you have classified it?
Yes & everyone on the blog at the time seemed to think it should be classified..

Does their classifying it sit well with you?
yes

Do you feel they stretched their own rules to rush to classify it?
Not at all. Clear as day on recon data before the vortex message..there was even a spontanious multible posting of the renumber event. It was inevitable by the data. They even waited til recon went though there the 2nd time.

If you believe it deserves classification does it not sit well with you to know other systems that match this same criteria have been left unclassified?
I haven't seen anything this season that looked like that that wasn't classified.


Just on that last point, 94L is better organized than TD13 and isn't classified.
Member Since: August 2, 2007 Posts: 19 Comments: 19234
2628. Dakster
Quoting FLdewey:
Guys calm down... at least we can all agree at this point TD 13 should be retired.


ROFLMAO!
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Houston here. I have never felt the call to become a wishcaster so strongly as I do now.
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2624. emcf30
Quoting Neapolitan:

See: non sequitur

LMAO
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Based on what happened with 93L becoming TD13, they should classify 94L too. It has higher T-numbers and a well-defined circulation, albeit exposed.
Member Since: August 2, 2007 Posts: 19 Comments: 19234
2622. Skyepony (Mod)
But the question is would you have classified it?
Yes & everyone on the blog at the time seemed to think it should be classified..

Does their classifying it sit well with you?
yes

Do you feel they stretched their own rules to rush to classify it?
Not at all. Clear as day on recon data before the vortex message..there was even a spontanious multible posting of the renumber event. It was inevitable by the data. They even waited til recon went though there the 2nd time.

If you believe it deserves classification does it not sit well with you to know other systems that match this same criteria have been left unclassified?
I haven't seen anything this season that looked like that that wasn't classified.


Great questions..btw
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Quoting TropicalAnalystwx13:
I'd be surprised if we weren't all banned by tomorrow morning, lol.

I'm out for the night guys, carry out the pointless argument about the argument, so Thunderpig can argue about the argument over the argument, and so on. I'll be on before school tomorrow to see how the tropics are doing, and also to see if the argument over the argument over the argument quit.



Thanks TA..
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Quoting CitikatzSouthFL:
Stopped in to see what opinions were on the tropics..Katia and the gulf. Found lots of bickering about whether or not the gulf has a TD. Get over it. Got declared a depression by the EXPERTS! Going to bed. Maybe the blog will be back on point in the morning. Goodnight children.

my thoughts exactly!
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New Orleans levees get a Failing Grade on the eve of a possible epic flooding event. Anyone want to put some money that the levees are breached in multiple places by next Thursday? I think the odds are rising rapidly that New Orleans will relive memories of 2005.......

http://www.nola.com/environment/index.ssf/2011/08 /new_orleans_levees_get_a_near-.html
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Quoting TropicalAnalystwx13:


For some unknown reason, reading that makes me LOL.
Quoting yoboi:
thanks for the info guys so NOLA could be in for major flooding......will they evacuate after 10 inches of rain????? they seem to worry more about cat size of a storm but looks like they should consider potenial rainfall also...just wow


If NOLA got 10" of rain no one would be able to evacuate because the streets would be flooded!! Rain totals are always a consideration here year round because of the drainage situation...when we have a tropical system on top of that it gets a little dicey...
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2613. HCW
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Stopped in to see what opinions were on the tropics..Katia and the gulf. Found lots of bickering about whether or not the gulf has a TD. Get over it. Got declared a depression by the EXPERTS! Going to bed. Maybe the blog will be back on point in the morning. Goodnight children.
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2611. scott39
Quoting FLdewey:


Clearly you've never been to San Diego.

If the official track holds true for "TD 13" Texas will not receive much rain... how cruel.
Ok, Then it shouldnt mean that and I still agree to disagree. I do agree however, that Texas will not get any mist off of TD 13.....Cruel indeed.
Member Since: June 13, 2009 Posts: 0 Comments: 6706
2610. KEEPEROFTHEGATE (Mod)
Quoting FLdewey:


Clearly you've never been to San Diego.

If the official track holds true for "TD 13" Texas will not receive much rain... how cruel.



so close but yet so far away
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where has all the tropical blogging gone... i read this blog for good information not arguments between others and right now this is over 50% argument. i want to know about tropical formation, not about drama between bloggers and thats pretty much all ive learned in the past two pages. just throwing it out there.
oh and why does katia's track keep suggesting a WNW track but it continues to head due west?
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Peace out
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Quoting KEEPEROFTHEGATE:
its really not moving much anywhere its to become semi quasi-stationary with a slow drift in a loop to w then nw then n then ne and it may then begin to drift se after ne turn sorta in a half a circle or something did i get that right not sure tricky poptenial is there if timing is right with convective cycles a formative tropical cyclone could dev if it lingers over open water longer than expected


all the while, sucking some heat out of that very warm water

cup half full perspective
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Evening everyone...just got home from Orlando! Just also, got the Website updated with TD13 Graphics, Models and Interactive Floaters Loops. Hope this helps you all!
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Quoting P451:


If I had a dollar for every time a record high or low temperature, record high or low precip event, or record high or low wind event was blamed on Global Warming I'd be a rich man.

If I had a dollar for every time the end of civilization was declared near due to Global Warming I'd be a rich man.

:)

Just sayin' Nea.

See: non sequitur
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2603. DFWjc
Quoting TropicalAnalystwx13:
I'd be surprised if we weren't all banned by tomorrow morning, lol.

I'm out for the night guys, carry out the pointless argument about the argument, so Thunderpig can argue about the argument over the argument, and so on. I'll be on before school tomorrow to see how the tropics are doing, and also to see if the argument over the argument over the argument quit.



night tropicalanalystwx13
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Quoting P451:


Yes.

But the question is would you have classified it?

Does their classifying it sit well with you?

Do you feel they stretched their own rules to rush to classify it?

If you believe it deserves classification does it not sit well with you to know other systems that match this same criteria have been left unclassified?


See, one thing I look to in an official entity is continuity. Tonight is an example of a break in that continuity to me.

And that simply does not sit well with me.


The storm, location, what it will and won't do, is inconsequential to the debate in my opinion.




Fortunately I was not on for most of the day so did not follow this at all but it is what it is. Frankly, it does not surprise me that the NHC made the call they did. If a system is borderline and that close to land I would err on the side of caution. After all, gulf coast residents might wake up to a TS in the morning and they are much more likely to pay attention to a TD tonight than a distubance.Less chance of being caught off guard if the unexpected happens overnight.

I remember when Dolly had 50 mph winds and the circulation opened up. Technically, the NHC should have discontinued the TS classification applying the empirical rules but they didn't and less than 12 hours later it closed off again. I am sure the purists were equally offended back then but a lot of this will become subjective at times.
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Quoting whepton3:


Man I tried to say that one time... that sometimes there's a political and public interest metric to some of NHC's statements... and I got nuked.

I think it was a good call.


Oh, I have said it before and I stand by my assertion that there are political concerns that the NHC is well aware of. They do a great job, but they are still a government agency. I think such concerns are applicable here.
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Quoting Orcasystems:




LOL
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Quoting ImitationDorito:


What's up with those coordinates?


They anticipate it will move WSW?
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Quoting Neapolitan:
If I earned a dollar every time someone here complained that the NHC had classified a storm they shouldn't have, I'd be a wealthy man. But if I had to pay a dollar every time someone here complained that the NHC had not classified a storm they should have--well, I guess I'd be back where I started. ;-)

Until and unless someone on this site can prove that they have even one-tenth as much education, knowledge, experience, wisdom, professionalism, and responsibility as the least senior person at the NHC where tropical weather is concerned, accusing anyone there of foul play is really just pointless and unfair sniping.


Lucid and well said.

+1563

These folks make decisions that have impacts on people's lives and property.

Tropical systems aren't lab rats, they kill people and have lasting impact on the lives of survivors.

It's why we have the NHC... to monitor and warn people about this stuff. They are imminently qualified to make their calls.
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2597. KEEPEROFTHEGATE (Mod)
Quoting TexasMariner:



I honestly am rather disappointed that they classified it. The low center is BARELY defined on sattlite and ascat respectively and it is very hard to tell where exactly it is let alone which direction it is moving. Best guess is that its somewhere north and east of the main convection. But its quite possible that this is not the dominant center and in fact a new circulation is forming under the main area of convection.


Really no idea where this thing is going or what it will do at this point, for all we know it could easily disappate in 24 hours.
its really not moving much anywhere its to become semi quasi-stationary with a slow drift in a loop to w then nw then n then ne and it may then begin to drift se after ne turn sorta in a half a circle or something did i get that right not sure tricky poptenial is there if timing is right with convective cycles a formative tropical cyclone could dev if it lingers over open water longer than expected
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2596. yoboi
how come they not sending in as much recon in the gulf as they did for irene????
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Quoting twincomanche:
+1 for the second time today. These people do a great job and we should be cheering for them not criticizing. Set up your own gig here for a year and see how you do against their record.

True that. It's human nature to play armchair quarterback from the comfort of your anonymous WU handle, I suppose; it's safe, and fun to some. But those senior forecasters at the NHC have to actually put their name--and their reputation--on all the pieces of data that could affect hundreds of thousands of people and billions in assets. The pressure must be unimaginable at times...
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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.