Unanswered questions concerning Hurricane Isaac

By: Dr. Jeff Masters , 4:35 PM GMT on August 31, 2012

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The top winds of Tropical Depression Isaac have fallen to 25 mph, but the storm continues to be a potent rain-maker as it heads north-northwest at 11 mph into Missouri. Isaac has spawned up to 20 suspected tornadoes, brought storm surges as high as 13.6' to the coast (in Lake Borgne, LA), and dumped 20" of rain at one station in New Orleans. The 13.27" of rain that fell at Hattiesburg, MS broke the record for wettest August in the city's history (previous record: 13.03" in 1987.) Major flooding is occurring on seven rivers in Louisiana and Mississippi. Isaac is being blamed for at least four deaths in the U.S., 24 in Haiti, and five in the Dominican Republic.

A few notable rainfall totals from Isaac, through 11 am EDT on Friday:

20.08" New Orleans, LA
15.02" Marion, MS
13.99" Pascagoula, MS
13.27" Hattiesburg, MS
10.85" Gulfport, MS
10.39" Slidell, LA
10.17" Biloxi, MS
9.85" Mobile, AL
7.38" Pine Bluff, AR
5.95" Baton Rouge, LA

A major reason for Isaac's heavy rainfall totals has been its very slow motion. This slow speed was due to the fact Isaac has been bumping into a ridge of high pressure that is unusually strong, due to the intense drought over the center of the U.S.; strong drought-amplified high pressure areas are very resistant to allowing any low pressure areas to intrude into their domain. The high pressure area was strong enough this week to allow several all-time records for heat this late in the year to be set:

112° on August 29 at Winner, SD
108° on August 29 at Valentine, NE
107° on August 29 at Corpus Christi, TX
97° on August 29 at Denver, CO (2nd highest so late in the year)


Figure 1. Nighttime view of Hurricane Isaac taken at 1:57 am CDT August 29, 2012, by the Visible Infrared Imaging Radiometer Suite (VIIRS) on the Suomi-NPP satellite. The VIIRS day-night band detects light in a range of wavelengths from green to near-infrared, and uses light intensification to enable the detection of dim signals. In this case, the clouds of Isaac were lit by moonlight. Image credit: NASA.

Isaac's beneficial rains falling in drought-stricken regions
Hurricanes get a lot of attention because of the billions in damage they cost, and the lives they disrupt. AIR Worldwide estimated today that insured damage from Isaac would cost up to $2 billion. This does not include damage to infrastructure or uninsured damage, so the final price tag of Isaac's rampage will be more like $3 - $5 billion. However, Isaac is now dumping beneficial rains over Arkansas, Missouri, Illinois, Indiana, Ohio, and Kentucky--regions stricken by the worst drought since the 1950s or 1930s, depending upon the exact location. These regions need 9 - 18 inches of rain to pull them out of drought. Isaac's 3 - 6 inches of rain will not end the drought, but will put a pretty good dent in it. I expect that 3 - 6 inches of rain for a wide swath of prime agricultural land in extreme drought is probably worth at least $5 billion, when you consider that a recent estimate by a Purdue economist put the cost of the great drought of 2012 at more than $77 billion. Only Hurricane Katrina ($146 billion) and the drought of 1988 ($78 billion) have been more expensive disasters, according to NOAA's National Climatic Data Center. Unfortunately, Isaac's arrival is poorly timed, as the storm is arriving during harvest season. The strong winds associated with the storm will flatten many crops, making it more difficult to harvest them, and Isaac's winds may cost farmers several hundred million dollars due to unharvestable crops. Still, the rains from Isaac will be highly beneficial for the success of the upcoming winter wheat season, and for next year's growing season.


Figure 2. Predicted precipitation for the five-day period ending on Tuesday evening shows that Isaac is expected to bring a large region of 3 - 6 inches of rain (red, orange, and brown colors) to Arkansas, Missouri, Illinois, Indiana, Ohio, and Kentucky. Image credit: NOAA/HPC.


Figure 3. The great drought of 2012 has brought so little rain to the Midwest that some areas require over 15" of rain (dark purple colors) to end the drought. Image credit: NOAA/CPC.

Unanswered questions about Hurricane Isaac

1. Did the passage of Hurricane Isaac stir up oil from the Deepwater Horizon oil spill? Isaac was the first hurricane to pass over the site of the 2010 Deepwater Horizon oil spill. We know that large hurricanes are capable of creating currents in deep water at the bottom of the Gulf of Mexico; Hurricane Ivan caused upwelling currents of 0.5 cm/s at a depth of about 500 meters. In an August 28 article in the Huffington Post, Nick Shay, professor of meteorology and physical oceanography at the University of Miami, said: "Winds will push water away from the center of a storm, which causes an upwelling as the ocean tries to adjust. It brings whatever is near the bottom up higher in the water column and currents can then push it towards the coast." Up to 1 million barrels of oil from the spill are estimated to still be present in the deep water sediment, on beaches, and in the marshes of Louisiana, and it is possible some of this oil will wash up on the Gulf Coast in coming months. The storm surge of Isaac also likely flushed out oil lodged in the coastal marshes of Louisiana, but it is unknown how much of a concern this might be.

2. What's the deal with these super-sized Category 1 and 2 hurricanes that have been hitting the U.S.? The past three landfalling hurricanes in the U.S.--Isaac (2012), Irene (2011), and Ike (2008)--have all been exceptionally large, among the top ten on record for horizontal extent of tropical storm-force winds. Each of these storms had an unusually low pressure characteristic of a storm one full Saffir-Simpson category stronger. Is this the new normal for U.S. hurricanes?

3. Did the new $14.5 billion upgrade to the New Orleans levee system cause worse flooding elsewhere? Whenever a new levee or flood control structure is created, you make someone else's flood problem worse, since the water has to go somewhere. Where did the water was stopped by the new $1.1 billion, 1.8 mile-long Lake Borgne flood barrier on the east side of New Orleans go? Did it flow south and contribute to the overtopping of the levees near Braithwaite? Or did it go north and contribute to the 36 hours of storm surge in excess of 5' observed along the Mississippi coast at Waveland? I posed this question to NHC's storm surge expert Jaime Rhome, and he said it was impossible to know without doing detailed storm surge modeling studies.

4. Can only hurricanes beginning with the letter "I" hit the U.S. now? Isaac (2012), Irene (2011), and Ike (2008) are the last three hurricanes to hit the U.S. It turns out that hurricanes that begin with the letter "I" and "C" have more names on the list of retired hurricanes than any other letter (nine each.) I'm thinking Isaac will get its name retired, letting storms beginning with "I" take over sole possession of first place on the retired storms list.

Hurricane Kirk in the Central Atlantic
Hurricane Kirk intensified into a 105 mph Category 2 hurricane this morning, becoming the 2nd strongest hurricane of the 2012 Atlantic hurricane season. Hurricane Gordon was the only stronger storm; Gordon hit sustained winds of 110 mph just before reaching the Azores Islands on August 18. Kirk has probably peaked in intensity, and is about to move over colder waters and gradually decay. Kirk is not a threat to any land areas.


Figure 4. Morning satellite image of Tropical Storm Leslie.

Tropical Storm Leslie a long-range threat to Bermuda, Canada, and the U.S. East Coast
Tropical Storm Leslie formed on Thursday in the Central Atlantic. Leslie's formation date of August 30 puts 2012 in 2nd place for earliest formation date of the season's 12th tropical storm. Only 1995 had an earlier formation date of the season's 12th storm. With records dating back to 1851, this year is only the second time 8 total storms have formed in August. The other year was 2004, when the first storm of the season formed on August 1 (Alex), and the 8th storm (Hermine) formed on August 29th. Satellite loops show that Leslie has a modest amount of heavy thunderstorm activity, and respectable low-level spiral bands and upper-level outflow. Conditions appear ripe to allow Leslie to intensify into a Category 2 hurricane by Sunday. Fortunately, Hurricane Kirk is weakening the ridge of high pressure to the north of Leslie, and Leslie is expected to turn to the northwest and miss the Lesser Antilles Islands. However, steering currents for Leslie are expected to collapse early next week, as Leslie gets stuck between two upper level lows. The storm will then slowly meander over the open ocean for many days, potentially threatening Bermuda. Leslie will stay stuck until a strong trough of low pressure approaches the U.S. East Coast around September 8. This trough should be strong enough to pull Leslie to the north and then northeast by September 9. At that time, Leslie may be close enough to the coast that the storm will make landfall in New England, Canada, or the Mid-Atlantic states. Leslie could also miss land entirely; this all depends upon the timing and strength of the September 8 trough of low pressure. Regardless, Leslie is expected to bring an extended period of high waves to the U.S. coast. According to NOAA's Wavewatch III model, large swells from Leslie will reach Bermuda by Monday, and arrive along the U.S. East Coast on Tuesday. These waves will be capable of creating dangerous rip currents and beach erosion.

Portlight disaster relief charity responds to Isaac
The Portlight.org disaster relief charity, founded and staffed by members of the wunderground community, are in Mississippi, helping out with Isaac relief efforts. You can check out their progress or donate to Portlight's disaster relief fund at the portlight.org website.

I'm planning on taking Saturday off, but will have a new post for you on Sunday. Have a great holiday weekend, everyone!

Jeff Masters

Hurricane Isaac Louisiana (apphotos)
People play in the storm surge from Hurricane Isaac, on Lakeshore Drive along Lake Pontchartrain, as the storm nears land, in New Orleans, Tuesday, Aug. 28, 2012. (AP Photo/Gerald Herbert)
Hurricane Isaac Louisiana
Portlight volunteers at Biloxi shelter (Portlight)
Portlight volunteers at Biloxi shelter
Hurricane Isaac Louisiana (apphotos)
Research students from the the University of Alabama measure wind speeds as Hurricane Isaac makes landfall, Wednesday, Aug. 29, 2012, in New Orleans, La. Isaac was packing 80 mph winds, making it a Category 1 hurricane. It came ashore early Tuesday near the mouth of the Mississippi River, driving a wall of water nearly 11 feet high inland and soaking a neck of land that stretches into the Gulf. The storm stalled for several hours before resuming a slow trek inland, and forecasters said that was
Hurricane Isaac Louisiana
TS Isaac (Raine911)
Between the rain bands
TS Isaac

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1722. guygee
Quoting seer2012:
The "Tropical Cyclone Forecaster's Guide",section 2.5,para. b discusses cold-core cyclones.The description seems to desribe Leslie's characteristics.Question for you experts,"Is this a cold core storm?"
There are many texts and papers that discuss cold-core cyclones. It does not take an expert to see that Leslie is almost certainly not a cold-core cyclone. I only say almost because "ground truth" is needed for certainty.
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GFS 42 hrs. ULL to the NE of Leslie, High to the NW, ULL over the Bahamas and ULL East of Leslie, Leslie also in a High Pressure environment = stall.

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Quoting CaicosRetiredSailor:



Leslie

There is some improvement, but not much. Still needs to do more work to re-gain strength.
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1719. pottery
Quoting barbamz:
What's bad with posting loops? I really want to know because loops can tell you a lot more than stills. Is it because a lot of persons are on phones and they got problems with loops?

I really hope that people don't stop posting loops.
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Quoting msphar:
I happen to live in Nevada near Tahoe. So I guess I also violate the 48 state rule. We don't get a lot of hurricane effects out here.

No Nevada doesn't get any hurricanes but heat/fires and winter storms you get.
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Leslie
Member Since: July 12, 2007 Posts: 0 Comments: 6069
1716. msphar
I happen to live in Nevada near Tahoe. So I guess I also violate the 48 state rule. We don't get a lot of hurricane effects out here.
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Quoting wxmod:
North America smoke and fires today. If you have a scratchy throat and itchy eyes, look up. It's pretty smokey in a lot of places.



Smoke on the east coast?

Also, Leslie's forecast track reminds me of Bertha (2008)... pretty much stalled out south of Bermuda before heading out to sea.


Became a decent sized storm.
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1714. ABlass
Quoting popartpete:
What to people do to get banned?


Break the Rules!
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1713. wxmod
North America smoke and fires today. If you have a scratchy throat and itchy eyes, look up. It's pretty smokey in a lot of places.

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Quoting msphar:
No idea what rule you are talking about TA13.

My focus is Salinas Bay, Puerto Rico

I just assumed you were in the USA for some odd reason. Most people think that if the storm gets above 20N before reaching 60W, it won't hit the Lower 48. Just ignore my previous comment.
Member Since: July 6, 2010 Posts: 113 Comments: 32814
What to people do to get banned?
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Convection looks to be covering up the LLC again.
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1709. msphar
No idea what rule you are talking about TA13.

My focus is Salinas Bay, Puerto Rico
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Quoting msphar:
She's above 20 East of 60, thats all I care about. Plus she is sheared and the LLC is exposed. Great news in my opinion.

That "rule" doesn't always hold.





Member Since: July 6, 2010 Posts: 113 Comments: 32814
re: 1704


Flood of the century in town
By Berkeley Springs, WV (Albums) Updated 2 hours ago

https://www.facebook.com/media/set/?set=a.4662682 80072209.109670.107892089243165&type=1
Member Since: July 12, 2007 Posts: 0 Comments: 6069
1706. msphar
She's above 20 East of 60, thats all I care about. Plus she is sheared and the LLC is exposed. Great news in my opinion.
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5 days on schedule and will almost be stationary.... up to 8PM thursday



Member Since: August 2, 2010 Posts: 21 Comments: 9882
parents house in Berkeley Springs, WV, now has 5 feet of water in the basement... Supposedly got 5" in one hour, though radar isn't telling that story. Creek (normal depth 4-6", 5' wide) rose 8'+ in one hour. Flooded all of downtown, parts of the school, and lots of businesses and homes as well.
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Quoting CaribBoy:
My hopes for rain are vanishing lol


Wet night for us on the islands... outer bands will bring showers...

Member Since: August 2, 2010 Posts: 21 Comments: 9882
My hopes for rain are vanishing lol
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Quoting sar2401:


Do we know he actually got banned? Seems to me that Taz was also supoosed to have been banned several days ago. I don't think the admins announce bans.

The off-topic meme that had good intentions about the amount of satellite loops we had been posting.
Member Since: July 6, 2010 Posts: 113 Comments: 32814
1700. sar2401
Quoting TheSundance:
Anybody here about TomTaylor getting banned? Poor guy


Do we know he actually got banned? Seems to me that Taz was also supoosed to have been banned several days ago. I don't think the admins announce bans.
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Oh my god i hate storms with a path like leslie's!! Don't even get a drop of rain!
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Quoting HurrMichaelOrl:
Evening everybody. Earlier, it was mentioned that the Saffir-Simpson Scale was modified this year, which led me to Wikipedia to read-up further. Though I know that Wiki info can be questionable, current information claims that two different Western Pacific Cyclones had sustained winds of 215 mph (Typhoon Ida and Typhoon Nancy). I had never read this before and had previously seen that the highest sustained winds of any recorded cyclone as 190 mph (Typhoon Tip and a couple others I believe).

Is there really any credibility to the report of 215 mph sustained winds?! What are everybody's thoughts on this?
I've heard of gusts like that from the most intense hurricanes, but not sustained windows. I suppose it could be possible.
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Tropical Storm LESLIE
...LESLIE TURNS NORTHWESTWARD WITH LITTLE CHANGE IN STRENGTH...
11:00 PM AST Sat Sep 1
Location: 20.2°N 58.4°W
Moving: NW at 18 mph
Min pressure: 998 mb
Max sustained: 65 mph
Member Since: July 12, 2007 Posts: 0 Comments: 6069
Quoting washingtonian115:
Have the NHC issued watches/warnings?.
I was wondering that too. Even if she goes north/northwest from here, there will still be bands over the northern islands. Seems a tropical storm watch would be warranted.
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if Is 98E becomes John and 99E Kristy, the location of John could be like this...

LOCATION: 100 MILES SW OF TROPICAL STORM KRISTY
????
lol
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these are very close to each other...
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Quoting goalexgo:
Not happening. That would equate to a central pressure of about 850 mb.


Yeah, I am skeptical of these reports too. I could believe sustained winds as high as 200 mph, but that is about it.
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1690. Gearsts
Quoting TropicalAnalystwx13:
Oh wait, I should probably remove this. I'll get banned for speaking my opinion.

Your alert is on red!
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1689. JLPR2
Station 41044 - South Atlantic
21.639 N 58.614 W

Not bad...
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Quoting HurrMichaelOrl:
Evening everybody. Earlier, it was mentioned that the Saffir-Simpson Scale was modified this year, which led me to Wikipedia to read-up further. Though I know that Wiki info can be questionable, current information claims that two different Western Pacific Cyclones had sustained winds of 215 mph (Typhoon Ida and Typhoon Nancy). I had never read this before and had previously seen that the highest sustained winds of any recorded cyclone as 190 mph (Typhoon Tip and a couple others I believe).

Is there really any credibility to the report of 215 mph sustained winds?! What are everybody's thoughts on this?
Not happening. That would equate to a central pressure of about 850 mb.
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Quoting sunlinepr:


We will have a super swell in the North....
In PR Aviones and Chata, won't be surfable...

Will have to move to La8, Puntas or even PineGrove... or Jobos...


PR will get some, probably not much for us in FL.
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1685. JLPR2
Quoting TropicalAnalystwx13:
Apparently it was. Banning somebody for one off-topic meme ever is just ridiculous. Especially when that blogger offers a lot of insight on the blog.


Especially when the blog is dead... Probably the reason why there were so many loops on the same page. XD
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Quoting GTcooliebai:
Old run 06z GFS shows Michael, Nadine, and Oscar. That would put us at 15 named storms with still 13 days left in Sept. and the whole month of Oct. where there is a secondary peak around Oct. 20th.


Hmm.. looks like Michael is going to be TX's storm.
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Quoting TropicalAnalystwx13:
Apparently it was. Banning somebody for one off-topic meme ever is just ridiculous. Especially when that blogger offers a lot of insight on the blog.

Next thing we know we'll be banned for briefly talking about our local weather instead of the tropics. Like something dramatic is going to change if somebody posts off topic for just a second.

I thought it was funny and there was a point, oh well. We know not to post memes after what happened to Geek and now Tom.
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Apparently it was. Banning somebody for one off-topic meme ever is just ridiculous. Especially when that blogger offers a lot of insight on the blog.

Next thing we know we'll be banned for briefly talking about our local weather instead of the tropics. Like something dramatic is going to change if somebody posts off topic for just a second.
Member Since: July 6, 2010 Posts: 113 Comments: 32814
Quoting Surferdude:
Was hoping to get a decent swell from Leslie...this hurricane season sucks big time :(


We will have a super swell in the North....
In PR Aviones and Chata, won't be surfable...

Will have to move to La8, Puntas or even PineGrove... or Jobos...
Member Since: August 2, 2010 Posts: 21 Comments: 9882
Old run 06z GFS shows Michael, Nadine, and Oscar. That would put us at 15 named storms with still 13 days left in Sept. and the whole month of Oct. where there is a secondary peak around Oct. 20th.

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Quoting TheSundance:
Anybody here about TomTaylor getting banned? Poor guy

Was it forever, I'm going to miss him.
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1678. JeffM
Any chance Leslie makes it to the US or does it look as though it's going to recurve sometime before?
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Giant filament explosion erupts on the Sun: massive CME to glance Earth’s magnetic field – Earth dodges dangerous bullet
Posted on September 2, 2012


September 2, 2012 – SPACE – Chance of flares: Sunspot AR1560 has more than quadrupled in size since August 30th, and now the fast growing active region is directly facing our planet: movie. NOAA forecasters estimate a 40% chance of M-class solar fares during the next 48 hours. A filament of magnetism curling around the sun’s southeastern limb erupted on August 31st, producing a coronal mass ejection (CME), a C8-class solar flare, and one of the most beautiful movies ever recorded by NASA’s Solar Dynamics Observatory: The explosion hurled a CME away from the sun traveling faster than 500 km/s (1.1 million mph). The cloud, shown here, is not heading directly toward Earth, but it could deliver a glancing blow to our planet’s magnetic field on or about September 3rd. This date is preliminary and may be changed in response to more data from coronagraphs on the Solar and Heliospheric Observatory (SOHO). – Space Weather

Member Since: August 2, 2010 Posts: 21 Comments: 9882
Quoting TropicalAnalystwx13:

Lol, ignoring somebody for posting a loop.


To be fair, 13 different loops of Leslie were posted in a short time, I have no issue with loops, but that many is overkill
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Evening everybody. Earlier, it was mentioned that the Saffir-Simpson Scale was modified this year, which led me to Wikipedia to read-up further. Though I know that Wiki info can be questionable, current information claims that two different Western Pacific Cyclones had sustained winds of 215 mph (Typhoon Ida and Typhoon Nancy). I had never read this before and had previously seen that the highest sustained winds of any recorded cyclone as 190 mph (Typhoon Tip and a couple others I believe).

Is there really any credibility to the report of 215 mph sustained winds?! What are everybody's thoughts on this?
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Quoting TropicalAnalystwx13:
Well Admin, that wasn't very nice.



what the admin do now
Member Since: May 21, 2006 Posts: 5091 Comments: 115454
Quoting sunlinepr:
Leslie stalls and turns into a major Cane...

Yes, that would be awesome and she stays out in the middle of the Atlantic.
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Quoting TheSundance:
Anybody here about TomTaylor getting banned? Poor guy

Well Admin, that wasn't very nice.

Please tell me it wasn't permanently.
Member Since: July 6, 2010 Posts: 113 Comments: 32814

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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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