Leslie near hurricane strength; Son of Isaac (90L) emerges in the Gulf

By: Dr. Jeff Masters , 3:05 PM GMT on September 05, 2012

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Tropical Storm Leslie is growing more organized and is approaching hurricane strength on its slow voyage northwards at 2 mph towards the island of Bermuda. Moderately high wind shear of 15 - 20 knots due to strong upper-level winds out of the northwest continues to keep most of Leslie's heavy thunderstorms pushed to the east side of the storm, but satellite loops show that Leslie now has an impressive blow-up of heavy thunderstorms with cold cloud tops near its center. Leslie's slow forward speed means that the storm is staying over the cold water stirred up by the storm's winds, inhibiting intensification, but the waters underneath Leslie are warm to great depth, making this less of a factor than usual. According to the latest SHIPS model forecast, the shear is expected to fall steadily today, reaching the low category, 5 - 10 knots, by Thursday afternoon. Leslie is over warm ocean waters of 29 - 30°C, and the reduction in shear and warm waters should aid intensification, and potentially allow Leslie to be at Category 2 strength at its closest pass by Bermuda Saturday night and early Sunday morning, as indicated by the official NHC forecast. The latest 11 am EDT NHC wind probability forecast calls for a 48% chance that Leslie will be a Category 2 or stronger hurricane Sunday morning at 8 am EDT. Leslie is a huge storm, and tropical storm-force winds are expected to extend outward from its center 250 miles by Friday. Bermuda is likely to see a 42-hour period of tropical storm-force winds beginning Saturday morning near 2 am AST, and lasting until 8 pm AST Sunday night. The official NHC forecast shows Leslie nearly making a direct hit on Bermuda, and Leslie will be capable of bringing an extended period of hurricane-force winds lasting six or more hours to Bermuda Saturday night through Sunday morning, should a direct hit materialize. NHC is predicting that hurricane-force winds will extend outwards from the center of Leslie by 35 miles on Thursday night, and I expect this will increase to at least 60 miles by early Sunday morning, when Leslie will be making its closest pass by Bermuda.


Figure 1. Morning satellite image of Tropical Storm Leslie. Heavy thunderstorms have built near the center of the storm, and Leslie is near hurricane strength.

Leslie's impact on Canada
Leslie will stay stuck in a weak steering current environment until a strong trough of low pressure approaches the U.S. East Coast on Saturday. The timing of this trough is such that Leslie will be pulled northwards and then north-northeastwards over the weekend. There are still significant differences among the models in the timing and speed of Leslie's track over the weekend, but we can now dismiss the threat of Leslie making a direct hit on New England. The storm is likely to make landfall in Nova Scotia or Newfoundland, though there are significant differences in the models' predictions of the timing of Leslie's arrival in Canada. The GFS model predicts an early Tuesday landfall in Newfoundland, but the ECMWF model is much faster and farther west, predicting a Monday afternoon landfall in Nova Scotia. Large swells from Leslie are pounding the entire Eastern Seaboard, and these waves will increase in size as Leslie grows in strength this week. The Hurricane Hunters are scheduled to make their first flight into Leslie on Thursday afternoon.


Figure 2. Morning radar image of Invest 90L off the coast of the Florida Panhandle.

Son of Isaac: Invest 90L emerges in the Gulf of Mexico
During Tropical Depression Isaac's trek across the center of the U.S. during the Labor Day weekend, the storm was ripped in half. One portion of the storm moved over the Northeast U.S., bringing heavy rains there, and another portion sank southwards over Alabama. You can see this split by studying an animation of the vorticity at 850 mb (the amount of spin at low levels of the atmosphere, near 5,000 feet above sea level) from the University of Wisconsin. This remnant of Isaac, which still maintained some of Isaac's spin, brought heavy rains of 5 - 10 inches that caused flooding problems over portions of Alabama on Tuesday. The storm has now emerged over the Gulf of Mexico near the Florida Panhandle, and was designated Invest 90L this morning by NHC. In their 8 am Tropical Weather Outlook, NHC gave 90L a 20% chance of developing into a tropical depression by Friday morning. According to NHC naming rules, "if the remnant of a tropical cyclone redevelops into a tropical cyclone, it is assigned its original number or name". Since "the remnant" refers to the primary remnant, and 90L does not fit the definition of a "primary remnant", the storm will be given a new name should it develop into a tropical storm, according to information posted on the NHC Facebook page. Esau or Jacob--the names of the sons of the biblical Isaac--would be fitting names for 90L, but the next storm on the list of Atlantic storms is Nadine.

Long-range radar out of Mobile, Alabama shows a large area of heavy rainfall along the coast due to 90L. The echoes do show some spiral banding behavior, but there is only a slight evidence of rotation to the storm. Infrared satellite loops show that the thunderstorms associated with 90L are not that vigorous and do not have particularly cold cloud tops, and the area covered by the thunderstorms is relatively small. Wind shear is a high 20 - 30 knots over the northern Gulf of Mexico, but is predicted to fall to the moderate range, 10 - 20 knots, by Thursday afternoon. Ocean temperatures in the Gulf have been cooled down considerably by the passage of Hurricane Isaac last week, and are 28 - 28.5°C. This is still plenty warm enough to support formation of a tropical storm, and I expect 90L will increase in organization on Thursday and Friday as it moves slowly south or south-southwest. 90L could become a tropical depression as early as Thursday, though Friday is more likely. A hurricane hunter aircraft is scheduled to investigate 90L on Thursday afternoon. A trough of low pressure and an associated surface cold front will move southeastwards over the northern Gulf of Mexico on Sunday, and this trough should be capable of pulling 90L to the northeast to a landfall along the Florida Panhandle or west coast of Florida on Sunday.


Figure 3. Morning satellite image of Tropical Storm Michael.

Tropical Storm Michael in the Central Atlantic
Tropical Storm Michael has strengthened to 50 mph winds, and appears to have a favorable enough environment to become a hurricane later this week. Satellite loops show that this is a small tropical cyclone, far out over the open Atlantic, and none of the models show that Michael will threaten any land areas.

Elsewhere in the Atlantic
The GFS and ECMWF models are predicting that a new tropical wave due to move off the coast of Africa on Friday will develop into a tropical depression by the middle of next week. It's too early to tell if this system might threaten the Lesser Antilles Islands.

Jeff Masters

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Quoting 954FtLCane:
at 440 hours Karen's ghostly remains are in the Carribean heading towards the Caymans..... just crazy I tell you.

Where is WKC when you need him...
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Member Since: August 6, 2011 Posts: 4 Comments: 40959
Quoting Grothar:
South Florida went from 1965 to 1992 without a Hurricane. In 1981 Dennis came from the South and I think the winds got up to about 20mph in Miami. That is a long time between storms.


Hey Gro....I think you may have forgotten one....David 1979...I believe it hit around Palm Beach somewhere....still been pretty darn lucky!!!!
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Member Since: August 6, 2011 Posts: 4 Comments: 40959
Quoting OcnGypZ:


Nornmally, no.. but then there's Oscar the Grouch..........................


There's a few of those here :)
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Quoting windshear1993:
humberto went to hurricane status so it shouldnt suprise you!!
The heat content in the gulf was way more different than it is now.
Member Since: August 14, 2010 Posts: 10 Comments: 17481
Member Since: August 6, 2011 Posts: 4 Comments: 40959
Quoting KoritheMan:


But as far as I know, peninsular Florida didn't go without a hurricane for that long. I daresay the current seven year trend without a hurricane on the peninsula is a new historical record.


I know Hurricane David hit in 1979, and South Florida was directly affected. Still, nothing compared to Betsy or Andrew.
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Quoting KoritheMan:
Henri of 2003 seems like the best analog for 90L to me for now.

Good analog, only difference here is that Henri was a tropical wave that got into the GOM, 90L has dropped down from the north and has parts of its roots from Isaac. Steering looks to be the same, question is will wind shear and dry air allow it to develop?
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Looks like we might have hurricane michael soon.

Member Since: November 19, 2010 Posts: 1 Comments: 1286
.............south florida is getting hit pretty hard this evening, been going on for quite awhile now
Member Since: August 6, 2011 Posts: 4 Comments: 40959
Quoting windshear1993:
humberto went to hurricane status so it shouldnt suprise you!!


Conditions were much different for Humberto. For now, 90L has northerly shear to contend with.
Member Since: March 7, 2007 Posts: 597 Comments: 21090
Quoting washingtonian115:
I know.I see Micheal is going to continue the trend of the males becoming hurricanes..and if the models are right so is Oscar.
Nadine could be the hurricane if 90L fails to become name.
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Quoting washingtonian115:
Watch people make Oscar Mayer's jokes.


Too late. I already have.
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Quoting washingtonian115:
The ships has gone mad bringing 90L to hurricane status.Lol.
humberto went to hurricane status so it shouldnt suprise you!!
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Quoting KoritheMan:


I still don't think Oscar sounds even remotely threatening. wtf?

I told you. It is. He's going to steal everybody's hot dogs. Do you know how evil that is?
Member Since: July 6, 2010 Posts: 113 Comments: 32524
Quoting GTcooliebai:
To be honest with you none of the names left on the list sound threatening, at least to me. When I think of Oscar I think of the Oscar Awards.
Patty and Rafael sounds threatening to me.
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Quoting GTcooliebai:
To be honest with you none of the names left on the list sound threatening, at least to me. When I think of Oscar I think of the Oscar Awards.


Rafael and William do.
Member Since: March 7, 2007 Posts: 597 Comments: 21090
Quoting GTcooliebai:
To be honest with you none of the names left on the list sound threatening, at least to me. When I think of Oscar I think of the Oscar Awards.


I think my name is pretty scary. :P Not very often we get to W though. :(
Member Since: November 19, 2010 Posts: 1 Comments: 1286
Quoting KoritheMan:


I still don't think Oscar sounds even remotely threatening. wtf?
To be honest with you none of the names left on the list sound threatening, at least to me. When I think of Oscar I think of the Oscar Awards.
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Quoting KoritheMan:


I still don't think Oscar sounds even remotely threatening. wtf?
Watch people make Oscar Mayer's jokes.Leslie didn't sound threatening but look at her now!.Has Bermuda right in her sites as a possibly strong hurricane.
Member Since: August 14, 2010 Posts: 10 Comments: 17481
Quoting KoritheMan:


I still don't think Oscar sounds even remotely threatening. wtf?


Nornmally, no.. but then there's Oscar the Grouch..........................
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Quoting KoritheMan:


Assuming it develops, probably anywhere between 40 and 60. And no, Henri weakened to a depression by the time it made landfall.


oh, oops lol
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Quoting Hurricanes101:


Henri had winds of 60mph when he made landfall, what do you think the intensity of 90L could be?

It will have a few days over water, so I think its best not to underestimate the intensity


Assuming it develops, probably anywhere between 40 and 60. And no, Henri weakened to a depression by the time it made landfall.
Member Since: March 7, 2007 Posts: 597 Comments: 21090
Quoting KoritheMan:
Henri of 2003 seems like the best analog for 90L to me for now.



Henri had winds of 60mph when he made landfall, what do you think the intensity of 90L could be?

It will have a few days over water, so I think its best not to underestimate the intensity
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Quoting presslord:


Oh, no, there's not!!!


90L to go north or west, Leslie to hit/miss Bermuda and then hit/miss Nova Scotia, Michael who is way out to sea and then the new waves coming off that bear watching. I read Dr. M's blog and thought back to when people were saying we wouldn't ever get this many storms this year and now we're looking at Nadine with more waves coming off Africa.
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Quoting washingtonian115:
I know.I see Micheal is going to continue the trend of the males becoming hurricanes..and if the models are right so is Oscar.


I still don't think Oscar sounds even remotely threatening. wtf?
Member Since: March 7, 2007 Posts: 597 Comments: 21090
Quoting allancalderini:
they always do that with invest they put them at hurricane strength btw the curse is finally broken a women name this year has become a hurricane.
I know.I see Micheal is going to continue the trend of the males becoming hurricanes..and if the models are right so is Oscar.
Member Since: August 14, 2010 Posts: 10 Comments: 17481
Interesting HPC Extended Forecast for Florida, summarized below:

EXTENDED FORECAST DISCUSSION
NWS HYDROMETEOROLOGICAL PREDICTION CENTER COLLEGE PARK MD
248 PM EDT WED SEP 05 2012

VALID 12Z SAT SEP 08 2012 - 12Z WED SEP 12 2012

[...]
WEATHER IMPACTS ANTICIPATED
===========================
EARLY ON, A CONVECTIVE LOW IS EXPECTED TO MOVE TOWARDS NORTHERN FLORIDA, BRINGING LOCALLY HEAVY RAINS TO THE EASTERN PANHANDLE AND NORTHERN FLORIDA PENINSULA SATURDAY NIGHT INTO SUNDAY. THE COLD FRONT WHICH SWEEPS THIS SYSTEM INLAND IS ANTICIPATED TO BRING MODERATE TO HEAVY RAINS FROM THE MID-SOUTH THROUGH THE NORTHEAST SATURDAY AND SUNDAY AND WHIP THROUGH THE FLORIDA PENINSULA BY NEXT TUESDAY, WITH COOLER CONDITIONS EXPECTED IN ITS WAKE. MODERATE TO LOCALLY HEAVY RAINS ARE POSSIBLE ACROSS FLORIDA DURING THE FRONT'S
PASSAGE THROUGH THE STATE.
[...]

Presumably the "convective low" is 90L/potential Nadine, we will have to see if she can actually get that far south into the GOM to become significant.

The frontal passage sounds "refreshing". Cooler conditions, come and get me.
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Quoting washingtonian115:
The ships has gone mad bringing 90L to hurricane status.Lol.
they always do that with invest they put them at hurricane strength btw the curse is finally broken a women name this year has become a hurricane.
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Quoting Grothar:
South Florida went from 1965 to 1992 without a Hurricane. In 1981 Dennis came from the South and I think the winds got up to about 20mph in Miami. That is a long time between storms.


But as far as I know, peninsular Florida didn't go without a hurricane for that long. I daresay the current seven year trend without a hurricane on the peninsula is a new historical record.
Member Since: March 7, 2007 Posts: 597 Comments: 21090
Quoting FloatingCity:


Nobody on this site gives a rats ass about anything that happens above New England, unless of course you are from the Motherland (Canada). This site is used by the Yanks, and to them, nobody else exists...thats why there isn't any talk about Leslie...doesn't affect the States...they don't care. Peace Brother!!


Odd thing to say after the person was saying WU is the place they go for information as LOCAL info was lacking!

Sounds like a miserable, jealous and disgruntled Brit. Most are lovely, but come across a few...and those ones always refer to Americans as 'Yanks'. Could be someone from somewhere else, but never heard anyone from other countries use that term. And TBH, most people are more concerned with what is going on in their own country (or region) than other places, def not JUST Americans, everyone...cause where you live will always be a major and first concern, for obvious reasons..it's your home.
Since being in the UK, many are just as clueless to worldly events as Americans...despite what everyone likes to portray as Americans being insular...def NOT the only ones.

*edit* and not saying I think Americans are insular! Being I am one especially LOL Just what many elsewhere believe...but it's the same everywhere, there will be sheep who are clueless whereever you go...
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South Florida went from 1965 to 1992 without a Hurricane. In 1981 Dennis came from the South and I think the winds got up to about 20mph in Miami. That is a long time between storms.
Member Since: July 17, 2009 Posts: 71 Comments: 26848
Quoting aislinnpaps:
Good evening, all. Quite a busy day of the season, a
smörgåsbord of storms to choose from and argue over.


Oh, no, there's not!!!
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The ships has gone mad bringing 90L to hurricane status.Lol.
Member Since: August 14, 2010 Posts: 10 Comments: 17481
Henri of 2003 seems like the best analog for 90L to me for now.

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Quoting wxchaser97:

I'm in the weak TS boat, I doubt 90L could become very close to a hurricane.


Is the shear supposed to be that high in the GOM (since it is early to mid September and it will be sitting over the GOM for 3-4 days? The water temps may no longer be high enough to support a major hurricane, but they should not be an issue for 90l to strengthen significantly.
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Quoting GTcooliebai:
I heard somewhere in here that it is still circulating the globe after all these year, quite comical if you ask me.


Yes and rumor has it she's rapping at the chamber door.
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Quoting RTSplayer:



1, The plants died a very, very long time ago (would vary somewhat by region).

Makes little difference what caused it, but pick a super -eruption or a meteor in the "relatively recent" geological past:

Toba
Taupo
Barringer Crater
Yellowstone
Any number of unknown volcanic collapses* or meteors.

Hawaii has evidence of a volcanic collapse that would have been one of the largest geologic events known.

Those are decent candidates for some of it I guess.

Probably no one event is to blame.

2, Some "Fossil Fuels" are mis-classified, as Methane exists in a stable form in enormous quantities on other planets and moons in our solar system, which clearly do not have life on them, nor were they ever capable of supporting life. So it's quite possible that much of this material has been where it is since the planet existed, or at least for a very long time and may not even be related to life in some cases.


Note:

Point 2 above is not acknowledged by the majority of mainstream scientists, even though I can point to Titan as absolute proof that it is possible.


Some interesting ideas there -- enough so that I thought it worth chipping out of lurking to comment :)

Re the plant death - there aren't any craters young enough and large enough to account for it due to meteorite impact - the Barringer crater is young, but it's really tiny. That said, it doesn't mean that there hasn't been a significant impact in recent times (well, for a given level of significant, at least!).

Before I moved out to Australia, one of the PhD students I knew was doing a fascinating study of impacts through water, using large gas guns (essentially a ~10 or 20m long, compressed gas gun that fired ball bearings at 5 km/s into targets, to model the formation of impact craters). It was kind of hard for her to get the water to stick to the wall, given that the gun fires horizontally, rather than vertically (too big and awkward to set a vertical gas gun up, from what I hear). Anyway, when she managed to get it set up, she found that you only need a depth of water approximately equal to the size of the impactor in order to prevent that impactor leaving any crater on the solid surface beneath the water. In other words, there could easily have been impacts in the oceans that we have no record of, because the impactor simply didn't leave a mark on the ocean floor. That said, it'd've left a damn great crater in the water - which would have re-equilibrated, causing huge tsunamis and all the rest, but no crater at the ocean floor. Add that to how hard it is to see through the ocean to find craters at the bottom, and you get the picture :)

As for the presence of hydrocarbons etc. as being native from Earth's formation - it's actually something we in Solar system astronomy and planet formation are very familiar with. In fact, if you look into the theories of the Earth's early atmosphere, you'll find it is thought to have been primarily CO2 and methane. The issue isn't with methane surviving in Earth's atmosphere for 4 Gyr, but rather methane and oxygen co-existing in Earth's atmosphere - you can have methane without oxygen, or oxygen without methane - but if you put both there, they would quickly try to achieve chemical equilibrium by reacting with one another 'till one or the other would run out. That's what methane only has a half-life on Earth of a few hundred years...

You can, of course, have abiogenic methane - but the point with the Earth is that, given our heavily oxygen rich atmosphere, any methane released to the atmosphere is essentially instantaneously destroyed (for a planet of age 4 billion years and a bit, a few hundred years is the blink of an eye).

All the discussion of methane clathrates beneath the arctic is pretty interesting to me, since a colleague of mine in France has spent the last five or six years studying clathrate hydrates as part of the formation and evolution of the satellites of the giant planets :) So it's fun to see them being discussed in a terrestrial sense for once :)
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Quoting Grothar:


Agree. But after it passes over Florida???

After it passes over FL then we will know:) It might as well just stat circulating the globe and reforming every once in a while.
Member Since: March 16, 2012 Posts: 127 Comments: 7958
Quoting MAweatherboy1:

It sure is. I have a feeling this isn't going to be the year, but it will happen eventually... It has to.
The run before this one had the storm recurving in the middle of the Atlantic as there was a pretty big gap left behind by Leslie and Michael, I'm wondering if that scenario will play out, especially if the storm can get going quickly. By the way I've been thinking watch it be a storm that develops in the NW Caribbean and takes a Wilma like track, pretty much picking up where we left off.
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Quoting ProgressivePulse:


Evening Sir.


At Ease! By the way, enjoyed the flood pictures, but don't you know you should stay inside and let someone else take them for you?
Member Since: July 17, 2009 Posts: 71 Comments: 26848
out of all the list for the atlantic hurricane season list 2 is the most active with 1980 1998 2004 and 2010 execept 1986 and 1992 which was the only el ninos for list 2 :) lets see what 2016 has in store!!
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Quoting wxchaser97:

I'm in the weak TS boat, I doubt 90L could become very close to a hurricane.


Agree. But after it passes over Florida???
Member Since: July 17, 2009 Posts: 71 Comments: 26848
Quoting GTcooliebai:
I heard somewhere in here that it is still circulating the globe after all these year, quite comical if you ask me.

Karen?
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Quoting GTcooliebai:
Makes you wonder when our luck will run out? 8 years is a pretty darn long time.
Sorry meant 7 years.
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Good evening, all. Quite a busy day of the season, a
smörgåsbord of storms to choose from and argue over.
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Quoting GTcooliebai:
Doubt a storm would recurve into a 1028 mb. ridge and a lack of troughiness, also the GFS loses resolution this far out, so it is hard to grasp any kind of pattern.

I would have doubts too, we can only go so long with out a landfalling major hurricane.
Member Since: March 16, 2012 Posts: 127 Comments: 7958
Quoting allancalderini:
the other list is the one used in 2009 this two list always have an El niño but there exception was in 2003 now ours looks to be 2012.
out of list one 1979 1985 and 2003 have been fairly active and did you know that list three just last year had 3 elninos in a row which is 1981 1987 and 1993 so list three recently started to get active starting with 1999,2005,2011 list 4 the curent list is right behind list three which had 1982 1994 and 2006
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Quoting GTcooliebai:
Makes you wonder when our luck will run out? 8 years is a pretty darn long time.

It sure is. I have a feeling this isn't going to be the year, but it will happen eventually... It has to.
Member Since: February 11, 2012 Posts: 84 Comments: 7941

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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.