TD 13 intensifying; Katia may pass uncomfortably close to U.S.

By: Dr. Jeff Masters , 3:28 PM GMT on September 02, 2011

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Tropical Depression Thirteen formed last night over the Northern Gulf of Mexico and is slowly intensifying, but isn't in a hurry to go anywhere. What TD 13 will do is dump torrential rains along the northern Gulf Coast over the next three or more days. So far, rain amounts along the coast have mostly been below one inch. At New Orleans Lakefront Airport, just 0.32" inches of rain had fallen from TD 13 as of 10 am CDT. Some coastal regions have received up to two inches, according to radar rainfall estimates. TD 13 is generating a large area of 30 - 35 mph winds over the Gulf of Mexico. At 7:20 am CDT, winds at the Mississippi Canyon 711 oil rig were southeast at 47 mph. This is above 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 35 mph. Latest surface wind observations from an Air Force hurricane hunter aircraft support leaving TD 13 as a tropical depression. Long range radar out of Mobile, Alabama shows heavy rain showers building along the northern Gulf Coast, but these rain showers are not well-organized into spiral bands. Strong upper-level winds out of the west-northwest are creating a moderate 10 - 20 knots of wind shear over TD 13, keeping the storm's heavy thunderstorms disorganized and pushed to the east side of the storm. However, latest satelllite loops show TD 13 is becoming increasingly organized, with a respectable spiral band forming on the southeast side, and an increase and areal coverage of heavy thunderstorm activity. This is very likely to be a tropical storm later today.


Figure 1. Radar-estimated rainfall from TD 13 from the New Orleans radar.


Figure 2. U.S. drought conditions on August 30. The rains from TD 13 have the potential to bring major drought relief to drought-stricken portions of the coast. Note how Eastern North Carolina is no longer in drought, thanks to the rains from Hurricane Irene. These rains also came close to putting out a persistent fire that had been burning in the Great Dismal Swamp near the Virginia/North Carolina border. Image Credit: U.S. Drought Monitor.

Forecast for TD 13
TD 13's large size, ill-formed circulation center, and the presence of dry air on its west side due to an upper-level trough of low pressure argue against rapid intensification of the storm for the next three days. Also tending to slow intensification will be the slow movement of the storm, which will allow cold water from the depths to rise to the surface, thanks to wind and wave action. Tropical cyclones strongly cool the water's surface when they pass over it, as seen in the time vs. depth chart of sea surface temperatures during Hurricane Irene's passage along the New Jersey coast (Figure 3.) However, the Gulf of Mexico has some very warm waters near TD 13 that extend to great depth (Figure 4), so the surface cooling imparted by TD 13 will be less than that seen for Hurricane Irene. As TD 13 moves closer to the coast, more and more of its circulation will be over land, which will also slow intensification. NHC's 11 am EDT wind probability forecast for TD 13 gave the storm a 23% chance of intensifying into a hurricane by Sunday. Assuming TD 13 does not attain hurricane strength, wind damage and storm surge damage will likely not be the main concern--fresh water flooding from heavy rains will be the most dangerous impact. Also of concern is the possibility of tornadoes. NOAA's Storm Prediction Center is currently not highlighting the Gulf Coast in their "slight risk" area for severe weather, due to the lack of enough solar heating to create instability. However, there will be plenty of wind shear in the lower part of the atmosphere that can potentially create spin in the coastal thunderstorms, and it is possible that as TD 13 intensifies, it may be able to generate several dozen tornadoes.

Coastal Louisiana, Mississippi, Alabama, and the extreme western Panhandle of Florida will likely receive very heavy flooding rains that will intensify Saturday and peak on Sunday. These rains should be able to put out the stubborn marsh fire east of New Orleans that has brought several days of air quality alerts to the city, but may cause moderate to severe flooding problems in other areas. The latest rainfall forecast from NOAA Hydrological Prediction Center shows that a large area of 15+ inches of rain is expected over Southeast Louisiana and coastal Mississippi. 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. 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°C), which will provide plenty of moisture for heavy rains, and plenty of energy to help TD 13 strengthen into a strong tropical storm. Steering currents will be weak in the Gulf this weekend and early next week, which will likely make the motion of TD 13 erratic at times.


Figure 3. EPA, in conjunction with Rutgers University and the NJ Department of Environmental Protection, has an Autonomous Underwater Vehicle (AUV, aka the Glider) deployed off the coast of NJ (since early August) continuously monitoring ocean temperature, density, salinity, sound velocity and dissolved oxygen at different depths. The AUV's path and data are displayed at the following website: http://marine.rutgers.edu/cool/auvs/index.php?did =221&view=imagery. The plot of temperature versus time above shows that in the weeks prior to the arrival of Irene, the ocean was heavily stratified, with warm waters of 24 - 26°C (75 - 79°F, red colors) extending from the surface to a depth of 10 - 15 meters. A sharp thermocline existed at a depth of about 15 meters, and ocean temperatures were colder than 14°C (57°F, dark blue colors) below the thermocline. The strong winds and high wave action of Hurricane Irene on August 28 - 29 stirred up cold water from the depths to the surface, cooling the surface waters to 17 - 19°C (63 - 67°F). In the days since the hurricane, surface waters have begun to warm again. Thanks go to Kevin Kubik, Deputy Director of the Division of Environmental Science and Assessment for EPA Region 2, for making me aware of this data.


Figure 4. The total amount of heat energy in the ocean available to fuel a tropical cyclone, in kilojoules per square centimeter of surface area. Tropical cyclones that move over ocean areas with TCHP values in excess of 70 - 90 kJ/cm^2 commonly undergo rapid intensification. Waters that are warm to a great depth have the highest TCHP, and the Loop Current that brings warm water northwards from the Caribbean to the Gulf of Mexico usually has the highest TCHP values in the Atlantic. Currently, we have an eddy that broke off from the Loop Current earlier this summer, now located a few hundred miles south of the Louisiana coast, that also has high TCHP values. Image Credit: NOAA/AOML.

Hurricane Katia
Hurricane Katia is continuing its long trek across the Atlantic Ocean today, and will not pose a danger to any land areas over the next five days. Katia is still struggling with dry air and moderate wind shear of 10 - 20 knots. Latest satellite loops show surface-based arc-shaped clouds racing to the southwest away from Katia's core, a sign that dry air is penetrating into Katia's thunderstorms and creating strong downdrafts that are robbing the storm of heat and moisture. Katia is over warm ocean waters of 28.5°C, and these waters will increase in temperature to 29°C over the next five days. Katia will pass well north of the region of cooler waters stirred up by the passage of Hurricane Irene last week.

The models are split on when the upper-level trough of low pressure bringing the wind shear to Katia will move away, and the storm may spend two more days battling wind shear and dry air before the upper-level trough pulls away to the north and allows Katia to intensify more readily. It is still unclear how much of a threat Katia may pose to the U.S., but it is becoming increasingly clear that Katia will pass uncomfortably close to the U.S. East Coast. The trough of low pressure currently steering Katia to the northwest will lift out early next week, and a ridge of high pressure is expected to build in, forcing Katia more to the west. This decreases the danger to Bermuda, but increases the danger to the U.S. A second trough of low pressure is expected to begin affecting Katia by the middle of next week, and will potentially recurve the storm out to sea before it hits the U.S. However, the models differ widely on the strength and timing of this trough. Meteorologist Grant Elliot of Australia's Bureau of Meteorology in Perth pointed out to me yesterday that the long-range forecast for Katia has more than the usual amount of uncertainty, due to the inability of the computer models to agree on what will happen to Tropical Storm Talas in the Western Pacific. Talas is expected to hit Japan early on Saturday as a strong tropical storm, then race northwestwards into the Bering Sea off the coast of Alaska. Talas is then expected to transition into a powerful extratropical storm in the waters south of Alaska. This storm will create a ripple effect downstream in the jet stream, all the way to North America, by early next week. The timing and amplitude of the trough of low pressure off the U.S. East Coast expected to potentially recurve Katia out to sea next week is highly dependent upon the strength of Tropical Storm Talas during its transition to an extratropical storm. The computer models are not very good at handling these sorts of transitions, leading to more than the usual amount of uncertainty in the long-range outlook for Katia. It will probably be another 2 - 3 days before the models will begin to converge on a solution for the long-term fate of Katia. Dr. Bob Hart's Historical Tropical Cyclone Probability web page suggests shows that tropical storms in Katia's current position have a 17% chance of hitting North Carolina, a 21% chance of hitting Canada, a 13% chance of hitting New England, and a 55% chance of never hitting land. One almost certain impact of Katia on the U.S. will be large waves. Long period swells from Katia will begin affecting the Bahamas on Sunday night, then reach the Southeast U.S. by Monday morning. By Tuesday morning, the entire U.S. East Coast will see high surf from Katia, and these waves will increase in size and power as the storm grows closer. Given the slow movement of Katia as it approaches the coast, plus its expected Category 1 to 3 strength as it approaches, the storm will probably cause extensive beach erosion and dangerous rip tides for many days.

94L
A well-organized low pressure system with a surface circulation but limited heavy thunderstorm activity due to high wind shear is 450 miles south of Halifax, Canada. This disturbance, (94L), is headed northeast out to sea, and is being given a 60% chance of developing into a tropical depression by NHC. 94L is under a high 25 - 30 knots of wind shear, but this shear is expected to fall to the moderate range, 10 - 20 knots, by Saturday morning. However, sea surface temperature will fall from 27°C today to 25°C Saturday morning underneath 94L, and the storm will have a very short window of time to get organized enough to get a name. At this point, it's really a subjective judgement call on whether or not 94L is already a tropical storm.


Figure 5. A Portlight volunteer works to clear storm debris from Hurricane Irene in Hollywood, Maryland.

Portlight disaster relief effort in Maryland
Hurricane Irene heavily damaged the town of Hollywood, Maryland, when a tornado cut off electric power, water, and phone service. Portlight and Team Rubicon volunteers arrived before emergency personnel, after following up on a local tip. What they found was an isolated area whose plight was unknown to the larger community. Most residents were trapped at their homes by heavy debris. Portlight and Team Rubicon worked for two days to clear paths to each address, extract vehicles from debris, and cut down trees that constituted safety hazards. Portlight also instructed local residents how to operate and maintain chainsaws and safely clear debris. No other volunteer organizations or emergency personnel arrived at any time, and Portlight succeeded in meeting the specific needs of the underserved, unserved, and forgotten. Visit the Portlight blog to learn more; donations are always welcome.

I'll have a new post each morning over the coming holiday weekend; wunderground meteorologists Angela Fritz, Rob Carver, and Shaun Tanner will be handling the afternoon and evening posts. Have a great holiday weekend, everyone!

Jeff Masters

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Quoting HoustonTxGal:
What is this large swirl in the center?




that would be Katia.
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1036. pcola57
That's right David.We will be on the"fetch" side of this GOM disturbance.Lot's of rain for the next couple of day's and then of course the clean-up and road repair will begin.I mention that because the worst thing you can do this weekend is to venture back out to the beach when no "all clear" has not been announced.I'm 5 Mile's inland and only 43' above sea level, so watch conditions closely and now that you have stumbled upon this website you can book mark it and keep abreast of the situation.There are many good posters in this blog but as per any blog there are the ones that don't know what they are talking about.You can tell the difference.Thanks for the question and I hope you keep visiting WunderGround.Be sure to let me know how your doing by coming here and posting this weekend.I realize that being 17 you consider yourself an adult but even adult's make bad choices.I can always run "down the road" to help you or get you the proper help.
V/R,
Moe
Member Since: August 13, 2009 Posts: 13 Comments: 6856
1034. Titoxd
Quoting loophole29902:
What happens if a greek alphabet named storm is retired? what do they do the next year?


Not going to happen, at least for what we typically consider "retired" (link).
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I just puked.
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Quoting HoustonTxGal:
What is this large swirl in the center?



That would be Katia.
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Quoting GTcooliebai:
12z CMC Link


Kinda ominous ain't it?

Like seeing all but the last two minutes of the scary movie wondering if they'll get away.
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Quoting TexasHurricane:


what does it show? I can't view it.


Shows Lee hugging the southern coastal states just inland about at a weak tropical storm or depression, then tracks it east all along the Gulf Coast to South Carolina. Then the run stops there where Katia is near the Bahammas. It's scenerio that WILL UNLIKELY happen, but still good entertainment.

Heres a link to it.

Link
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What is this large swirl in the center?


Member Since: September 18, 2007 Posts: 0 Comments: 1074
1028. IKE
Tallahassee afternoon discussion....

SATURDAY NIGHT THROUGH SUNDAY NIGHT...MOISTURE/DYNAMICS ASSOCIATED
WITH THE TROPICAL STORMS WILL SLOWLY PUSH FURTHER EAST AND
NORTHEAST. THIS TREND WILL BRING LIKELY TO CATEGORICAL POPS FURTHER
EAST AS WELL...WITH MOST OF THE FORECAST AREA EXPERIENCING AT LEAST
LIKELY POPS BY SUNDAY AFTERNOON. THROUGH SUNDAY NIGHT...THE
POTENTIAL IS CERTAINLY THERE FOR SOME LOCALLY HEAVY RAIN TOTALS.
HIGHEST RAIN POTENTIALS WILL BE ACROSS THE WESTERN ZONES WITH A
GENERAL 2-4 INCHES IN THE GRIDS. AMOUNTS WILL TAPER OFF FURTHER
NORTH AND EAST TO LESS THAN AN INCH ALONG THE I-75 CORRIDOR OF
GEORGIA. OF COURSE...MORE RAINFALL IS EXPECTED INTO MONDAY AND THESE
LOWER TOTALS TO THE EAST ARE LIKELY TO RISE BY THAT TIME. DEPENDING
ON JUST HOW T.S. LEE EVOLVES AND WHERE THE MORE ORGANIZED RAIN BANDS
SETUP...LOCALLY HIGHER AMOUNTS OF RAINFALL WILL CERTAINLY TO
POSSIBLE. WILL WAIT ANOTHER MODEL CYCLE OR TWO BEFORE DETERMINING
WHERE AND WHEN FLOOD WATCHES MAY BE NEEDED.
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Quoting loophole29902:
What happens if a greek alphabet named storm is retired? what do they do the next year?

thats one of the best questions I have ever seen on this website! Good questions!
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What happens if a greek alphabet named storm is retired? what do they do the next year?
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At. 1017. Idk wonderin.
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First time posting, so please excuse my less than perfect knowledge. Been lurking for a few years. Started lurking after Dennis loosened my shingles, Katrina finished the job and dropped them in our pool and Wilma took the blue temporary tarp and swing set. I agree with sflweatherguy. I was one of those that thought Andrew wouldn't come our way. Was I wrong! Here in S Florida we all have our accordian shutters, standby generators and always stock up on hurricane supplies for the season. This season is testing our preparedness and I'm justsaying looks like all our hard work just might pay off this season. With all these storms passing just East of us, one of them might just stop by and give us a rude awakening!
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Quoting HoustonTxGal:


Looks like my 3 year old has been into the markers again!


seems some are still on the TX/LA

I know Storm W said something about that on his blog.
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BLOG UPDATE:

Tropical Storm Lee & Hurricane Katia
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1018. JNCali
12Z Euro run makes Katia look like a yo-yo... a really big one
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Quoting JrWeathermanFL:

Dry air:
Killed Don sort of
Killed Emily sort of
Trying to kill Katia
Trying to kill Lee
BTW wheres Taz?


idk, why? lol.
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Quoting ILwthrfan:


That would be a GREAT life saving scenerio for the south and TEXAS! but then at the end it turns to DOOM...lol Trying to re-emerge off the South Carolina shore and then do a FUJIWARA battle with Katia, although Katia would likley eat up that depression or remenant low.


what does it show? I can't view it.
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Quoting GTcooliebai:
12z CMC Link
Looks like Katia is after Lee in that run, chasing him down.
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Quoting NOLALawyer:


He is talking about Bob Breck (Robert Zebrecki) a local NOLA TV met who wears a bad rug and has a pretty decent grasp of tropical weather. He is also pretty corny and loves to say things like "Gully Washer!"

I trust the NHC and Norcross quite a bit more than Bob.

Mike
Iremember while living there he would talk about getting the 'muggys.' That guy cracked me up.
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Quoting TropicalAnalystwx13:


Nah, really?

Honestly, land is SUPPOSED to kill tropical cyclones. That has nothing to do with the season.

Dry air:
Killed Don sort of
Killed Emily sort of
Trying to kill Katia
Trying to kill Lee
BTW wheres Taz?
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1011. IKE
NAM @ 18 hrs...


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Afternoon all!! Lee it is!
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Looks like my 3 year old has been into the markers again!
Member Since: September 18, 2007 Posts: 0 Comments: 1074
Quoting JrWeathermanFL:
Land and Dry air:
Killed Arlene
Killed Don
Killed Emily
Killed Harvey
Trying to kill Katia
Trying to kill Lee
Boy, that leaves 6 or so storms


Nah, really?

Honestly, land is SUPPOSED to kill tropical cyclones. That has nothing to do with the season.
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Quoting GTcooliebai:
12z CMC Link


That would be a GREAT life saving scenerio for the south and TEXAS! but then at the end it turns to DOOM...lol Trying to re-emerge off the South Carolina shore and then do a FUJIWARA battle with Katia, although Katia would likley eat up that depression or remenant low.
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Quoting wolftribe2009:


I am a bit confused on what this person and Bob is talking about. I see Lee still dumping loads of rain (Yes 10-20 inches of rain) on Louisiana, Mississippi and Alabama. The Panhandle of Florida and Georgia also included in that I believe.


He is talking about Bob Breck (Robert Zebrecki) a local NOLA TV met who wears a bad rug and has a pretty decent grasp of tropical weather. He is also pretty corny and loves to say things like "Gully Washer!"

I trust the NHC and Norcross quite a bit more than Bob.

Mike
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Land and Dry air:
Killed Arlene
Killed Don
Killed Emily
Killed Harvey
Trying to kill Katia
Trying to kill Lee
Boy, that leaves 6 or so storms
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1003. IKE
Trough is gonna pick it up. I noticed the 12Z ECMWF has sped up Lee, compared to yesterdays 12Z run, to the NE or NNE once it finally makes landfall.
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Member Since: September 18, 2007 Posts: 0 Comments: 1074
1000. Oct8
Quoting ILwthrfan:


This storm is a drought buster. I don't think we will see anything above a 75 mph storm worse case scenerio. Preparations need to be made in low lying areas. Anywhere from Baton Rouge to just north of Tallahasee FL will get an easy 6" of rain with isolated amounts over a foot. This is going to be a wet system, but it has many factors going against it.

This storm will have dry air issues all through its life cycle do to the position of it near the coastlines.

Also its huge size will only accelerate dry air into its environment, a bit like Irene had along the east coast, only this storm is no where near the strength of her.

People need to take neccessary preparations as there are factors that people need to be VERY wary of, mainly flooding.


Probably a wet wet event but I thought she was stalled. I mean "He." So it will take awhile to know his intensity at landfall.
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Quoting HCW:
This storm looks like an STD not that I have ever experienced one of those before :)


ewwww
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Quoting DavidHOUTX:


and it flooded a lot!

Nah, Hurricane Jerry didn't drop very much rainfall. I feel like you may be thinking of Tropical Storm Allison (the 1989 version).



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Is there such a thing as "Miraclecasting" We need it.
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Lee is warm cored, tropical storm..

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995. IKE
Lee looks to be getting going better on satellite.
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Quoting Matt1989:
the dry air this year is ridiculous.


Something to get used to when the average global temperatures continue to increase year after year resulting in much longer and in more intense heat waves.

Might be something to dig into with tropical cyclone research. Does the increase in global temperature neccesarily increase the # storms and storm strengths or does it load the atmosphere with more SAL resulting from geographical dessertification? That factor may result in increase number of storms with decrease of MAJORS do to the fact that storms are constantly in a dry air environment with boiling hot waters under them.
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993. HCW
This storm looks like an STD not that I have ever experienced one of those before :)
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Quoting GTcooliebai:
12z CMC Link

Last frame is a bit scary...
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Good afternoon all.

Lee looks, well I wouldn't say impressive, but "nice". It should continue to organize over the northern Gulf of Mexico, and may make a run at hurricane status by the end of the weekend. At this time, I think a 50-60 mph tropical storm at peak can be expected at this time, but may definitely go higher if it spends more time over water.
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990. IKE
Bastardi from 5 hours ago about Lee...


Joe Bastardi
They call it 1006 at 27.5 and 91. cloud loop shows its rapidly coming together
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Quoting Dodabear:
Any one seen StormW lately or NRAamy?


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Quoting 1900hurricane:

Hopefully you are right, but October storms in Texas are fairly rare due to the pattern changes and increased troughiness that fall brings. The last one we've had was in 1989.


and it flooded a lot!
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12z CMC Link
Member Since: August 31, 2009 Posts: 0 Comments: 5628

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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.