Isaac approaching hurricane strength

By: Angela Fritz , 9:14 PM GMT on August 27, 2012

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Isaac is walking the line of hurricane status this afternoon after a hurricane hunter mission investigated the storm and found winds of 80+ mph with the SFMR instrument, which looks down at the surface from the plane and estimates what wind speeds are. This instrument has a notoriously rough time in doing so when there's heavy rain, and since the strongest winds were recorded coinciding with the strongest rain, you can imagine that this region of high wind speed could be suspect. The hurricane hunter mission is still in the storm, so I imagine they will issue a special update if needed. Currently the best estimate of wind speed within the storm is 70 mph. Isaac's pressure has been dropping today as well and is now 981 mb. Isaac is moving northwest at 12 mph--no change since this morning. Satellite loops show that Isaac remains large, though asymmetric, with most of the strong thunderstorm activity on the west and southwest side. Isaac's southeast side continues to struggle with dry air and wind shear, which could help to moderate Isaac's intensity as it approaches the coast.

An oil platform in the northern Gulf of Mexico is reporting sustained winds from the north-northeast at 40 mph this afternoon. A buoy west of Tampa, Florida is recording sustained winds around 30 mph, and platforms south of Louisiana are recording winds from 35-40 mph. The widespread heavy rain of yesterday has lightened up in Florida, but a strong line of thunderstorms in one of Isaac's outer bands is training northward along and offshore of the east coast of Florida, affecting everyone from Miami to Jacksonville.

This afternoon the AP reported that Isaac's death toll in Haiti jumped to 19, which puts Isaac's total death count at 21. It appears most of the deaths in Haiti were due to collapsing structures.


Figure 1. Satellite imagery of Tropical Storm Isaac around 3pm EDT on Monday.

Track forecast:
Models seem to be coming into better agreement today on where Isaac will make landfall, closing in on Louisiana and New Orleans as most likely landfall point. The ECMWF, HWRF, and UKMET all suggest New Orleans as the landfall location. The GFS is only slightly west of that. The GFDL is the farthest west, predicting landfall near the Louisiana-Texas border. Landfall timing remains Tuesday night. Beyond landfall, Isaac is expected to move north toward the Midwest through the rest of this week, however, models are showing that the system will likely slow down around landfall time, prolonging impacts like surge and inland flooding.

Intensity forecast:
The closer Isaac gets to landfall without having formed an eye, the better it is for intensity at landfall. Isaac has strengthened only modestly in the past 24 hours, and is still struggling with a less-than-conducive atmospheric environment. The HWRF remains on the high end of the intensity spectrum, suggesting Isaac will be a weak category 2 upon landfall. Other models suggest it will be a strong category 1, but the difference is splitting hairs. The National Hurricane Center's official forecast is for Isaac to continue strengthening over the next day, reaching category 2 at landfall.


Figure 2. Tide gauge data from St. Petersburg, Florida. The green line shows the storm surge. As Isaac's counterclockwise winds blew offshore this morning, water levels feel two feet at St. Petersburg. The winds switched to onshore this afternoon as the center of Isaac moved more to the northwest, bringing a storm surge of two feet to the city.

Storm surge observations from Isaac
This morning, as Isaac's counter-clockwise winds brought offshore winds to the Tampa/St. Petersburg area, ocean waters fell two feet along the coast. This afternoon, winds have shifted to blow onshore, and a two foot storm surge has been observed at Naples, Fort Meyers, and St. Petersburg on the west coast of Florida. Water levels have also begun to rise along the coast of Louisiana, with a storm surge of 1.5 feet already occurring at Shell Beach on the east side of New Orleans in Lake Borgne.

Angela and Jeff

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Quoting tomas5tex:
This and the last 2 fixes has shown a west trend. Maybe a wobble...then again maybe something else. Also pressure is down again since last fix.


me: 07:26:00Z
Coordinates: 27.3167N 87.9833W
Acft. Static Air Press: 843.9 mb (~ 24.92 inHg)
Acft. Geopotential Hgt: 1,302 meters (~ 4,272 feet)
Extrap. Sfc. Press: 977.8 mb (~ 28.87 inHg)
D-value: -
Flt. Lvl. Wind (30s): From 4° at 2 knots (From the N at ~ 2.3 mph)
Air Temp: 21.1°C (~ 70.0°F)
Dew Pt: 20.4°C (~ 68.7°F)
Peak (10s) Flt. Lvl. Wind: 5 knots (~ 5.8 mph)
SFMR Peak (10s) Sfc. Wind: 20 knots* (~ 23.0 mph*)
SFMR Rain Rate: 2 mm/hr* (~ 0.08 in/hr*)


Maybe Isaac running from the dry air to his northeast?
Member Since: September 18, 2010 Posts: 0 Comments: 5248
Time: 07:26:30Z
Coordinates: 27.3167N 87.95W
Acft. Static Air Press: 842.9 mb (~ 24.89 inHg)
Acft. Geopotential Hgt: 1,304 meters (~ 4,278 feet)
Extrap. Sfc. Press: 977.4 mb (~ 28.86 inHg)
D-value: -
Flt. Lvl. Wind (30s): From 178° at 7 knots (From the S at ~ 8.0 mph)
Air Temp: 21.1°C (~ 70.0°F)
Dew Pt: 20.9°C (~ 69.6°F)
Peak (10s) Flt. Lvl. Wind: 9 knots (~ 10.3 mph)
SFMR Peak (10s) Sfc. Wind: 20 knots (~ 23.0 mph)
SFMR Rain Rate: 3 mm/hr (~ 0.12 in/hr)
(*) Denotes suspect data
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977mb found a good distance from wsw of last storm loc
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This and the last 2 fixes has shown a west trend. Maybe a wobble...then again maybe something else. Also pressure is down again since last fix.


me: 07:26:00Z
Coordinates: 27.3167N 87.9833W
Acft. Static Air Press: 843.9 mb (~ 24.92 inHg)
Acft. Geopotential Hgt: 1,302 meters (~ 4,272 feet)
Extrap. Sfc. Press: 977.8 mb (~ 28.87 inHg)
D-value: -
Flt. Lvl. Wind (30s): From 4° at 2 knots (From the N at ~ 2.3 mph)
Air Temp: 21.1°C (~ 70.0°F)
Dew Pt: 20.4°C (~ 68.7°F)
Peak (10s) Flt. Lvl. Wind: 5 knots (~ 5.8 mph)
SFMR Peak (10s) Sfc. Wind: 20 knots* (~ 23.0 mph*)
SFMR Rain Rate: 2 mm/hr* (~ 0.08 in/hr*)
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The last I saw Kirk, he was just northwest of Puerto Rico heading wnw or nw.
Member Since: September 18, 2010 Posts: 0 Comments: 5248
Quoting weatherh98:



It will steadily deepen through landfall, because the pressure could get as low as 970

the fact that the nhc cant find high winds is perplexing


The reason there are no high winds is that there is no tight pressure gradient. From the recon images posted by Levi, 100 miles from the storm the pressure is around 999 and going down steadly to 995, then 990, then 988, with 55mph winds all the way in. When you get closest to the center the winds actually are decreasing because the loose eye is 44 miles in diameter, according to the hurricane hunters. The pressure is then decreasing more rapidly to 982, but the 6mb drop is not enough to support a hurricane-force eye.

If the system continues west and bumps into the high pressure ridge in Texas the pressure gradient could get steep on the west side even if the storm does not strengthen much. Resulting in high winds on what is usually the weaker (west) side of the hurricane.
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Quoting odinslightning:



i just don't want the oyster house and other places down by the causeway to get hurt....and i dont want the downtown area flooded cuz that would f**k up the bars....

i am very glad this thing didn't bomb as much as it could have if the dry air hadn't have interfered....


Concur on all fronts.

I think Tacky Jacks is staying open as long as it makes sense for them...??

Closing the old tunnel in the a.m...

Will get some rising water, Felix's et al are up high enough on stilts that they'll be fine...downtown will get alot of rain, likely...if anything like Miami on Monday. Ugh.
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Maybe if we ignore pre-Kirk, it might develop into a nice predictable hurricane. A lot of people got burned out pretty bad watching, predicting, and expecting Ernesto (though he didn't disappoint in the end) and Isaac (conclusion pending) to actually develop into a hurricane.
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Tom...........how long were you up at Mammoth Mountain?
Member Since: September 18, 2010 Posts: 0 Comments: 5248
Quoting CoastalAlabama:
More "fun" after 2 a.m.:

TWC:

"Hurricane Irene is anticipated to land fall at approximately 5:30 p.m. local NYC time."

vs.

"T.S. Isaac is coming in around dinner time tomorrow night."


Unanticipated cultural bias? What are they saying, that southerners need to manage their timetables and events around the food trough? Let's be more succinct moving forward: "You should expect about 2 inches in the Wal-Mart and up to 3 at Ryan's, 3 at Waffle House, and 4 at the piggly wiggly. You need to begin preparations NOW."

;-)





i just don't want the oyster house and other places down by the causeway to get hurt....and i dont want the downtown area flooded cuz that would f**k up the bars....

i am very glad this thing didn't bomb as much as it could have if the dry air hadn't interfered....
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Tom..........
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2343. jake436
Nevermind...thought it would show what I had pulled up. Apparently not. You can google map it and see what I'm talking about. But yes, that's what happened in Hurricane Betsy. That's the worst case scenario, actually...a big storm pushing water up the river. Either that, or a big storm coming from east to west into Lake Ponchartrain, forcing water from the Lake into NOLA.
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More "fun" after 2 a.m.:

TWC:

"Hurricane Irene is anticipated to land fall at approximately 5:30 p.m. local NYC time."

vs.

"T.S. Isaac is coming in around dinner time tomorrow night."


Unanticipated cultural bias? What are they saying, that southerners need to manage their timetables and events around the food trough? Let's be more succinct moving forward: "You should expect about 2 inches in the Wal-Mart and up to 3 at Ryan's, 3 at Waffle House, and 4 at the piggly wiggly. You need to begin preparations NOW."

;-)


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2341. jake436
Link

This is google map of Venice, LA, the mouth of the river. You'll see what I mean looking at this.
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Watching spray and some waves coming over the wall at Lake PON.The Dude better be carefull.
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Quoting sar2401:

But it's not real money, just a bunch of zeros and ones. I'm not sure there's any real money left, except maybe Vegas. :)


LOL U amay be right!
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2338. jake436
Quoting sar2401:


It takes a crapload of water to make the Mississippi overflow its banks. It's usually things like everything in the Great White North melting at once that cause problems, not the rain from a storm the likes of Isaac.
I don't think he was talking about rain. He was talking about surge.

You just reminded me of the Weather Channel in Gulfport the night before Katrina, talking about the rain bands coming onshore, and the GOM starting to come up from the rain. SMH. Yes, 3" of rain is filling up the entire GOM...lol.
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Quoting sar2401:


It takes a crapload of water to make the Mississippi overflow its banks. It's usually things like everything in the Great White North melting at once that cause problems, not the rain from a storm the likes of Isaac.


Was just thinking about storm surge.
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2336. sar2401
Quoting HurricaneHunterJoe:


Better give Mitt the heads up,he has bookoo bucks stashed there.

But it's not real money, just a bunch of zeros and ones. I'm not sure there's any real money left, except maybe Vegas. :)
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2335. jake436
Quoting HurricaneHunterJoe:


Maybe I should rephrase, If the river were at normal water levels?
Well yes. Something to realize. The river is not one channel that goes from Minnesota to the GOM. Once it gets below NOLA, you have the Miss River Delta, with fingers going in every direction. The 'land' between the river and the GOM to the east and west is nothing but shallow marsh, a lot of it floating. So although on a map it looks like the water/surge would be pushed up from the south only, actually, the water is pushed into the river from any direction the storm comes from. Moving east to west, there are several large passes that can funnel water straight in from the gulf, and the exact same thing from the west, should a storm come from that direction. Then you have 3 HUGE passes that come from the south. It's like the river is three rivers below Venice. So again, from whatever direction it comes, water is pushed directly into the river.
There is literally NO land down there anymore. I'm 43. In my lifetime, I have seen the disappearance of the land in this area. At Empire, LA, there is a bridge on Hwy 23 as you head down to Venice. Less than 20 years ago, when heading south over the bridge, looking to the west, there were 3 completely separate bays. Now, look to the west and its just...water. As far as the eye can see. The only thing preventing THAT water from getting into the river is the levee. But once you get below Venice (virtually unpopulated below Venice), there are no levees, and you can cross from the west side of the river to the east just by jumping across the passes. In fact, one of the passes is called "The Jump".
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2333. sar2401
Quoting HurricaneHunterJoe:


Maybe I should rephrase, If the river were at normal water levels?


It takes a crapload of water to make the Mississippi overflow its banks. It's usually things like everything in the Great White North melting at once that cause problems, not the rain from a storm the likes of Isaac.
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Quoting sar2401:


Robert, you're such a pessimist. One of these monster CV storms is going to crush the Cayman Islands, I can just feel it in my bones. :)


Better give Mitt the heads up,he has bookoo bucks stashed there.
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Quoting sar2401:


Kirk has a lot of dry air in front of him...doesn't that sound familiar? There's also a huge weakeness to his north created partially by all the blowoff from Isaac. In a normal season, I'd say he's going to weaken, turn north towards the weakness, and become a fish. This season, I can predct, with absolute confidence, that we will still be talking about when Kirk is going to make landfall in time for the end of the regular baseball season. :)


lol....
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2330. sar2401
Quoting robert88:
I am done looking at this pathetic dried out mess of a storm. The SAL and dry sinking air have spread far into the W Atlantic basin this season. The trade winds have been insane and It seems every storm has had a hard time consolidating and getting vertically stacked... ULL's all over the place too. Environmental conditions have been horrible for the most part and they don't look like they will be getting much better anytime soon.


Robert, you're such a pessimist. One of these monster CV storms is going to crush the Cayman Islands, I can just feel it in my bones. :)
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2329. jake436
Quoting HurricaneHunterJoe:
Say Isaac attains hurricane status at 90mph. He is a big storm.Say he hits the Louisiana coast just west of the Mississippi River. Does his storm surge have enough power to back up the river causing it to overflow it's banks down there to cause flooding?
Link
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Quoting jake436:
Ha...the river could use the water, bro. You realize they have LARGE sections of the Mississippi CLOSED due to not enough water to float barges?


Maybe I should rephrase, If the river were at normal water levels?
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2327. sar2401
Quoting odinslightning:
i was thinking about the total amount of dry air so i decided to look at the tropical atlantic WV loop....look how much water Isaac is slinging across the Atlantic in venting....

http://www.ssd.noaa.gov/goes/east/tatl/flash-wv.h tml

Link


anyone know what effect that is going to have on the overall conditions since we are just at the beginning of the peak cane season?



Kirk has a lot of dry air in front of him...doesn't that sound familiar? There's also a huge weakeness to his north created partially by all the blowoff from Isaac. In a normal season, I'd say he's going to weaken, turn north towards the weakness, and become a fish. This season, I can predct, with absolute confidence, that we will still be talking about when Kirk is going to make landfall in time for the end of the regular baseball season. :)
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Quoting nofailsafe:


Depending on average trajectory, probably 36 hours.

I reckon a minimal category one storm by landfall if that.


Thanks :)
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I am done looking at this pathetic dried out mess of a storm. The SAL and dry sinking air have spread far into the W Atlantic basin this season. The trade winds have been insane and It seems every storm has had a hard time consolidating and getting vertically stacked... ULL's all over the place too. Environmental conditions have been horrible for the most part and they don't look like they will be getting much better anytime soon.
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man im watching this coverage from new orleans local stations and also mobile on direct tv.........whenever a commercial comes on they go to a different station..... ............... :) Direct TV
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Quoting TexNowNM:
If Isaac were to actually go the the Tx/La border what do any of you think the strength would be and at what time would you put landfall.

Thanks


Depending on average trajectory, probably 36 hours.

I reckon a minimal category one storm by landfall if that.
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2322. jake436
Quoting HurricaneHunterJoe:
Say Isaac attains hurricane status at 90mph. He is a big storm.Say he hits the Louisiana coast just west of the Mississippi River. Does his storm surge have enough power to back up the river causing it to overflow it's banks down there to cause flooding?
Ha...the river could use the water, bro. You realize they have LARGE sections of the Mississippi CLOSED due to not enough water to float barges?
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Quoting TomTaylor:
hah god no. Got like 5hrs of sleep last night, hiked several miles during the day, and then sat in a car for 8hrs...I should probably go to bed now, but I'll stick around


ok......me..........the uninformed will carry the torch..........lol
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2320. sar2401
Quoting GTcooliebai:
Well that's it for me guys be back later today. Have a goodnight all. By the way the GFS continues to insist on Kirk although weaker on this run.



GN, GT. Now we have to go through this all over again with Kirk. I'm going to find another hobby...maybe butterfly collecting or something like that. :)
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i was thinking about the total amount of dry air so i decided to look at the tropical atlantic WV loop....look how much water Isaac is slinging across the Atlantic in venting....

http://www.ssd.noaa.gov/goes/east/tatl/flash-wv.h tml

Link


anyone know what effect that is going to have on the overall conditions since we are just at the beginning of the peak cane season?

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Quoting sar2401:


Yeah, me neither. I'm not waiting for the 5am update on this hot mess, that's for sure.
hah god no. Got like 5hrs of sleep last night, hiked several miles during the day, and then sat in a car for 8hrs...I should probably go to bed now, but I'll stick around
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Say Isaac attains hurricane status at 90mph. He is a big storm.Say he hits the Louisiana coast just west of the Mississippi River. Does his storm surge have enough power to back up the river causing it to overflow it's banks down there to cause flooding?
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Another laugh about TWC throughout the day:

Along with my newfound knowledge of skin tags, I have been reminded about 28 times that the picture I am looking at on the screen shows the N. Gulf land mass and the Florida peninsula...with white squiggly lines to augment and highlight the need to show me where the northern gulf states are and where Florida is.

And that Obama 'approved' the emergency requests for Louisiana.

I needed to know that, of course.
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I WANT SOME WEATHER ITS DEAD BORING IN THE NE CARIB!!!!!!!!!!!!!!!!!!!!!!!!!
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If Isaac were to actually go the the Tx/La border what do any of you think the strength would be and at what time would you put landfall.

Thanks
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2313. sar2401
Quoting Kumo:


Cool beans. :)

Speaking of which, my Wife just fed our newborn girl. Now is a good time to get some sleep while I can. Goodnight and hope folks stay safe over in NOLA.


GN, Kumo, and congrats on the new little daughter. Enjoy her now while you can....she'll be 16 in about two months. :)
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2311. sar2401
Quoting TomTaylor:
I'll be around for a little. Don't want to stay up too late though as I'm already tired


Yeah, me neither. I'm not waiting for the 5am update on this hot mess, that's for sure.
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2310. Kumo
Quoting sar2401:


Keeper of the Gate says his blog is still up so apparently he wasn't banned. He may be doing what all the other sane people are doing at this hour....sleeping. :0


Cool beans. :)

Speaking of which, my Wife just fed our newborn girl. Now is a good time to get some sleep while I can. Goodnight and hope folks stay safe over in NOLA.
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2309. sar2401
Quoting dixiegal1:
img src="Photobucket">
One more try for some laughs:)


LOL. Good one, Dixie.
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Quoting TomTaylor:
Agreed. The ECMWF had been winning with Isaac earlier on. It was calling for a central Gulf coast landfall well before any of the other models picked up on the solution. Lately it has been rather inconsistent and has literally been playing catch up to the GFS. First it switched to the Panhandle solution, then the GFS flipped to Louisiana, and now the ECMWF is doing the same.

Check out the 00z GFS from last night




Check out tonight's 00z ECMWF




Intensity and track are practically identical. Good ol' game of catch up



bada boom............LOL
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2307. sar2401
Quoting listenerVT:
Any chance that's a completed eyewall I see? (Mind you, I'm seeing it on an iPhone screen. LOL!)


That's Steve Jobs visiting from the other side. :) No closed eye or eyewall found by recon.
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Quoting xtremeweathertracker:
Ok i may get bashed for this....BUT....the last 4 fixes..one from the previous mission and 3 from the current show a rough heading of 285 to 290 degrees!! Am i wrong...is this a jog or trend?? *Covers head and ducks*


Did you sign up for the 2 week trial? It's available to anyone,just cancel before 2 weeks,has some good stuff on there.
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Quoting sar2401:


Hey, Tom, you starting the night shift?
I'll be around for a little. Don't want to stay up too late though as I'm already tired
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img src="Photobucket">
One more try for some laughs:)
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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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