Isaac slamming Gulf Coast with damaging floods, tornadoes

By: Dr. Jeff Masters , 4:44 PM GMT on August 30, 2012

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Slow-moving Tropical Storm Isaac continues to hammer coastal Louisiana, Mississippi, Alabama, and Florida's Panhandle with tornadoes, torrential rains, high winds, and a damaging storm surge. Over the past 24 hours, destructive tornadoes have touched down in Biloxi and Pascagoula, Mississippi, and one person was killed by a tree falling on a car in Pearl River County, Mississippi. A major flood event is occurring in Slidell, Louisiana, where Isaac's storm surge filled Bayou Bonfouca and the W-14 Canal, inundating portions of the city with 1 - 5 feet of water. While Isaac is now a weakening minimal-strength tropical storm, it is still a potent rainmaker, and will cause damaging floods all along its path for the next three days. Major river flooding is occurring or is about to occur on a number of rivers in the landfall area. In north central Tangipahoa Parish in southeast Louisiana and southwestern Pike County in southern Mississippi, a mandatory evacuation has been ordered for all low-lying areas and along the Tangipahoa River, due to the potential failure of the Lake Tangipahoa dam. Audubon Park in New Orleans, recorded 11.19" of rain as of 7 pm Wednesday night. An earlier amount of 19" was found to be erroneous, and this is not a 24-hour precipitation record for the city. According to wunderground's weather historian, Christopher C. Burt, New Orleans' greatest 24-hour rainfall on record is 14.01" on July 24 - 25, 1933. The Louisiana official state 24-hour record is 22.00" on Aug. 29, 1962 at Hakberry, although U.S. Army Corps of Engineers `Storm Studies' mentions a 23.80" falling in a 24-hour period at Millers Island during a TS on Aug 7-8, 1940. Storm total was 37.50" over a 60-hour period there during that event.

A few other rainfall totals from Isaac, through 11 am EDT on Thursday:

15.02" Marion, MS
10.09" Hattiesburg, MS
10.15" Gulfport, MS
9.80" Slidell, LA
9.74" Biloxi, MS
8.52" Mobile, AL
5.57" Baton Rouge, LA


Figure 1. Isaac's winds and storm surge overcomes the seawall and floods South Beach Boulevard in Waveland, Miss., Wednesday, Aug. 29, 2012, the seventh anniversary of Hurricane Katrina hitting the Gulf Coast. (AP Photo/Rogelio V. Solis). Waveland experienced a storm surge in excess of 5' for 36 hours.

Isaac's storm surge winds down
Storm surge levels along the coast of Mississippi and surrounding areas are gradually receding, and the surge has finally fallen below 5' at Waveland, which experienced a storm surge in excess of 5' for 36 hours. Isaac's storm surge levels were characteristic of a Category 2 hurricane, and lasted for an exceptionally long period of time. Waveland, Mississippi experienced a peak surge of 8' and peak storm tide of 9' (surge plus the natural high tide), which beat the levels that occurred during Category 2 Hurricane Gustav of 2008 (7' of storm tide.) The peak 11.06' storm surge at Shell Beach, which is in Lake Borgne, 30 miles southeast of New Orleans, exceeded the 9.5' surge recorded there during Gustav. According to an article in nola.com, Isaac pushed a storm surge of 13.6' into Lake Borgne, on the east side of New Orleans. This is not far from the 15.5' storm surge Hurricane Katrina brought to the location. It is quite possible that Isaac's storm surge might have breached levees of the east side of New Orleans, flooding areas inhabited by tens of thousands of people, had the Army Corps of Engineers not completed their $14.5 billion upgrade to the New Orleans flood defenses this year. I estimate that storm surge damage from Isaac will exceed $2 billion. Isaac has likely caused $2.5 billion in insured damage not related to flooding, insurance firm Eqecat estimated yesterday. Here were some of the peak storm surge values that were recorded at NOAA tide gauges during Isaac:

11.1' Shell Beach, LA
8.0' Waveland, MS
3.5' Pensacola, FL
4.6' Pascagoula, MS
3.8' Mobile, AL


Figure 2. A TRMM satellite 3-D view of rainfall on Aug. 28 showed a few very powerful thunderstorms near Isaac's eye were reaching heights of almost 17 km (10.6 miles.) Intense bands of rain around Isaac were occasionally dropping rain at a rate of over 2.75 inches per hour. Image credit: SSAI/NASA, Hal Pierce.

Isaac's storm surge on the Mississippi River
A storm surge estimated at 12' moved up the Mississippi in Plaquemines Parish near Port Sulphur, LA, near 8:30 pm EDT Tuesday, causing overtopping of the levees and flooding of homes in the mandatory evacuation areas behind the levees. These levees were not part of the $14.5 billion levee upgrade New Orleans got after Hurricane Katrina, and were not rated to Category 3 hurricane strength, like the levees protecting New Orleans are. Since salt water is more dense than fresh water, the surge travelled along the bottom of the river, with the fresh water flow of the river lying on top. The surge continued upriver, and before reaching New Orleans, encountered an underwater barrier in Plaquemines Parish. This barrier was constructed by the Army Corps of Engineers beginning on August 15, in order to keep salt water from moving upstream and contaminating drinking water for Plaquemines Parish and New Orleans. Salt water had made it 90 miles upriver to the outskirts of New Orleans, due to the low flow rate of the river (which had dropped 7' below average in height due to the drought of 2012.) According to a spokesperson for the National Weather Service River Forecast Office, this barrier was probably able to completely block the flow of salt water upriver due to Isaac's storm surge, and no salt water made it as far as New Orleans. However, the massive intrusion of ocean water into the river channel caused the mighty Mississippi's fresh water flow to back up for hundreds of miles. Water levels were elevated by 10' in New Orleans (103 miles upstream from the mouth of the Mississippi), 8' in Baton Rouge (228 miles upstream), and 1.4' at Knox Landing, an amazing 314 miles upstream.

Hurricane Kirk in the Central Atlantic
Hurricane Kirk intensified into a 75 mph Category 1 hurricane this morning, becoming the busy 2012 Atlantic hurricane season's fifth hurricane. With the season's mid-point of September 10 still almost 2 weeks away, we've already had 12 named storms and 5 hurricanes, which is close to what an entire season experiences in an average year (11 named storms and 6 hurricanes.) Kirk should stay well out to sea and not trouble any land areas.


Figure 3. Morning satellite image of Hurricane Kirk.

Tropical Storm Leslie forms in the Central Atlantic
Tropical Storm Leslie has formed in the Central Atlantic. Leslie's formation on August 30 puts 2012 in 2nd place for earliest formation date of the season's 12th 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. Leslie is organizing quickly, and appears destined to become a hurricane before the week is out. 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. In the long term, it remains unclear if Leslie will follow Kirk and fully recurve out to sea. The latest 2 runs of the GFS model have predicted that Leslie will recurve out to sea and not threaten any land areas, but the latest 2 runs of the ECMWF model have predicted that the trough of low pressure pulling Kirk to the northeast will not be strong enough to recurve Leslie out to sea. Instead, the ECMWF predicts that a ridge of high pressure will build in early next week, forcing Leslie more to the northwest, making the storm a potential threat to Bermuda, then to the Northeast U.S. and Canada in 8 - 11 days.

Jeff Masters

Hurricane Isaac Louisiana (apphotos)
Two men walk in the storm surge from Isaac, on Lakeshore Drive along Lake Pontchartrain, as the storm approaches landfall, in New Orleans, Tuesday, Aug. 28, 2012. (AP Photo/Gerald Herbert)
Hurricane Isaac Louisiana
west palm beach flood isaac (alishu)
West Palm Beach flood from Isaac
west palm beach flood isaac
Hurricane Isaac Impacts Navarre Beach & Pier10 (jennjeff1)
Hurricane Isaac versus Navarre Beach Pier, the longest concrete pier on the Gulf of Mexico
Hurricane Isaac Impacts Navarre Beach & Pier10

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1188. Skyepony (Mod)
Quoting JLPR2:
What could we make of this?
Isaac sized circulation?



It's another big one..
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1187. Skyepony (Mod)
Quoting wxchaser97:

That isn't good, like FL needs more of that. Is that still Isaac related or something else?


Looks like some Isaac outflow & afternoon showers. One little spot had 3". I have to wonder if some drainage wasn't blocked..
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1186. kabloie
Quoting Grothar:
By the way, we cannot refer to Kirk as "Captain Kirk" If you remember, he was promoted to Admiral in Star Date 2306.2. I thought you people kept up on these things?


And I'm expected to know that how? I've been marooned on Ceti Alpha 5 for quite some time now.
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1185. JLPR2
What could we make of this?
Isaac sized circulation?

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I'm out for the night/morning. Kirk and Leslie should be different later in the morning.
Member Since: March 16, 2012 Posts: 127 Comments: 7928
1183. JLPR2
Interestingly the GFS has rain totals of 1-2inches for the NE islands courtesy of Leslie.

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Quoting Skyepony:
I had heard there was flash flooding in Orlando, FL today but dang..


That isn't good, like FL needs more of that. Is that still Isaac related or something else?
Member Since: March 16, 2012 Posts: 127 Comments: 7928
1181. Skyepony (Mod)
I had heard there was flash flooding in Orlando, FL today but dang..

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Quoting Hurrihistory:
Leslie looks a little weaker tonight as she continues to move due West. If she stays weak she may not make the turn to the NorthWest in time, so the folks in the Islands need to be ready to act! My Goodness, could the NHC be wrong in their prediction of a turn to the North?

I think Leslie will begin to go WNW and in a couple days NW and then NNW. The islands should prepare as Leslie should be a hurricane by then and anything could happen.
Member Since: March 16, 2012 Posts: 127 Comments: 7928
Quoting zosimo:
America is in deep trouble if its civilians are not able to handle a barely CAT 1 hurricane! The hysterical media coverage, 'specially by TWC, of this rain storm was an embarrassment (sp?). NBC buying TWC was the worse thing to happen to TWC. Its all about ratings for NBC so hype Isaac and shame TWC on air staff to promote Isaac as if its gonna be the end of LA/MS as we know it.
And for the president to go on nationwide TV to promote his concern for a piker of a Hurricane was also a shame. If Americans need to rely on the President of the USA for guidance on how to deal with a dinky hurricane then America is in deep do-do.
It was stunning to hear the consideration for retiring the name Isaac has been mentioned. Based on this event?-give me a break. It rained alot with the wind never really being a factor and thats reason enough to retire the name Isaac?!
The NHC center has had egg on its collected faces as it was wrong with its projections basically for Isaacs entire existence. Even the slowest of slow could see an eye was not forming for Isaacs entire existence. No eye of any significance means no hurricane maybe a TS.
And finally it is obvious that America is getting soft if how media and people react to the Isaacs and Irenes of this world as both were clearly not going to be the end of the world weather events but thats how its being promoted by government and media these days.
I dread the day when a CAT 4 or 5 gets into the Gulf, and heads for landfall in the US. The government and media reaction to this will be off the charts. IF Wolf Blitzer on CNN can label Isaac a 'national crisis' without any challenge to that claim then will Wolf et al think when the eventual CAT 4 or 5 gets into the Gulf-its the end of the world?

You hit the head on the nail!! These are exactly my thoughts. I am also waiting for that "zinger" of a storm that will really be a crisis, what they have here with Isaac is "child's play" compared to what a cat 4 or 5 will be like.
Member Since: May 12, 2012 Posts: 11 Comments: 2403
Quoting Grothar:
By the way, we cannot refer to Kirk as "Captain Kirk" If you remember, he was promoted to Admiral in Star Date 2306.2. I thought you people kept up on these things?

Ok so Admiral Kirk is wrapping some stronger convection and making his eye a little clearer. Is that better or can we go back to Captain, that was something I honestly didn't know though:D
Member Since: March 16, 2012 Posts: 127 Comments: 7928
1177. JLPR2
It seems we have some technical difficulties over here. XD

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Leslie looks a little weaker tonight as she continues to move due West. If she stays weak she may not make the turn to the NorthWest in time, so the folks in the Islands need to be ready to act! My Goodness, could the NHC be wrong in their prediction of a turn to the North?
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From the NHC website:
For Atlantic hurricanes, there is a list of names for each of six years. In other words, one list is repeated every seventh year. The only time that there is a change is if a storm is so deadly or costly that the future use of its name on a different storm would be inappropriate for obvious reasons of sensitivity. If that occurs, then at an annual meeting by the committee (called primarily to discuss many other issues) the offending name is stricken from the list and another name is selected to replace it.
Member Since: March 16, 2012 Posts: 127 Comments: 7928
1174. JLPR2
Quoting Grothar:
By the way, we cannot refer to Kirk as "Captain Kirk" If you remember, he was promoted to Admiral in Star Date 2306.2. I thought you people kept up on these things?


Never been a fan of Star Trek, I'm more of a Star Wars kind of guy. XD

But very well then, Admiral Kirk's northern eyewall is looking better.
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Quoting Grothar:
By the way, we cannot refer to Kirk as "Captain Kirk" If you remember, he was promoted to Admiral in Star Date 2306.2. I thought you people kept up on these things?

Well I'm not really into that stuff so I wouldn't know. Though Captain Kirk sounds catchier than Admiral Kirk for a hurricane.
Member Since: March 16, 2012 Posts: 127 Comments: 7928
1172. Grothar
By the way, we cannot refer to Kirk as "Captain Kirk" If you remember, he was promoted to Admiral in Star Date 2306.2. I thought you people kept up on these things?
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Quoting Grothar:


Tromba marina, allan.
Yeah I knew the name in spanish It cause some damage in the city and in the port the high winds were terrible.
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1170. JLPR2
Quoting allancalderini:
I mean this one anyone has answer for this one.


If they request it I don't see why they wouldn't be retired.
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Quoting ScooterXX7:


But thats how it should be. Igor didn't warrant retirement. $200 mil in damages? 1 death? Barely a scrape of a landfall? Really?

We might as well as run out of names by 2050 then.



Storms need to be considered in the context of the regions that they affect. As others have pointed out, just because that isn't significant at all for a US landfalling storm does not mean that other nations have the same storm standards.

In the case of Igor, no 1 death and $200mill isn't much compared to many other storms, however, in context it was extremely significant.

In Canada's report to the World Meteorological Organization, it was stated to be a storm without parallel in the island's history. This was only the second time that the Meteorological Service of Canada had requested for a hurricane name to be retired (the first was Hurricane Juan in 2003). The hurricane is also considered a probable benchmark for future cyclones in the region, having illustrated to residents that they are not immune from hurricanes and their impacts. Link

Same applies to other storms as well.
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Quoting allancalderini:
Lol that is ok I imagine the place you are is 1:00am meanwhile in here is 11:00 pm

Yeah it is and I've been regularly staying up this late. I'm in trouble when schools starts in a week. Luckily I get to skip 1st hour since I'm doing an independent study in meteorology.
Member Since: March 16, 2012 Posts: 127 Comments: 7928
1167. JLPR2
Makes you wonder just what happened to El NiƱo, eh?

July 30th:


August 30th:
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1166. Grothar
Quoting allancalderini:
Thanks Gro.


Tromba marina, allan.
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Quoting wxchaser97:

Your welcome, sorry I didn't even see your original question until you quoted yourself:)
Lol that is ok I imagine the place you are is 1:00am meanwhile in here is 11:00 pm
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Quoting allancalderini:
Thanks but I confuse with other question that I was asking thanks guys.

Your welcome, sorry I didn't even see your original question until you quoted yourself:)
Member Since: March 16, 2012 Posts: 127 Comments: 7928
Quoting ScooterXX7:


I've been lurking here since 2005. Trust me.

Hey, I've been lurking for a few years and only joined this year. There are plenty hurricanes that weren't discussed on here for retirement, I'm too tired to list.
Member Since: March 16, 2012 Posts: 127 Comments: 7928
Quoting allancalderini:
Btw Do Mexico retire storms? I have look all the hurricanes that have affect only Mexico and the only one retires are Diana in 1990 and maybe Roxanne in 1995.
I mean this one anyone has answer for this one.
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Quoting allancalderini:
anyone has answer for this?
you mean a waterspout?
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Quoting Grothar:


Waterspout
Thanks Gro.
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Quoting wxchaser97:

Waterspout? Anyway I have and it wasn't too bad but since it was in my town it wasn't fun either.
Quoting JLPR2:


A water spout, if they move onto land they then become tornadoes.
Thanks but I confuse with other question that I was asking thanks guys.
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Quoting JustSouthofEquator:


So it would Majorly Cutesy Captain Kirk then?

Whatever we want to call it, it will be warp speed ahead when that front/trough picks him up.
Member Since: March 16, 2012 Posts: 127 Comments: 7928
1157. tillou
After being through Cindy in '05 and Issac '12 I would say isaac will be upgraded toa cat 2.

I live in Ama 70031 zip 70031

Trees and telephone poles down and snapped here and there. Had some guest I would say were just over 100 around 3am tues . The house was creeking when it happened

Will post some video when power cones back
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1156. Grothar
Quoting allancalderini:
anyone has answer for this?


Waterspout
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Quoting GTcooliebai:
252 hrs. Nova Scotia is next.



At 5 days out, the error cone on a hurricane is about 1000 miles wide.

At 252 hours out, you might as well start reading tea leaves. :)
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1153. 2ifbyC
Quoting OracleDeAtlantis:
Brave words for a man whose stage has been stolen by the planet he tempts.


Sip some salt water Kool Aid! Da booze isn't doin' ya much good...

Politics aren't welcomed here.
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Quoting wxchaser97:
Anyway Captain Kirk is still looking very impressive and will likely begin our count for major hurricanes.


So it would Majorly Cutesy Captain Kirk then?
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1151. JLPR2
Quoting allancalderini:
anyone has answer for this?


A water spout, if they move onto land they then become tornadoes.
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Quoting allancalderini:
anyone has answer for this?

Waterspout? Anyway I have and it wasn't too bad but since it was in my town it wasn't fun either.
Member Since: March 16, 2012 Posts: 127 Comments: 7928
Quoting wxchaser97:

That is not true, we don't say every landfalling hurricane could be retired. You've got to think out some things before coming on here and expecting something good.


I've been lurking here since 2005. Trust me.
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Quoting GTcooliebai:
What an infamous year that was, Andrew also struck that same year.
USA was hit by both sides Atlantic and Pacific.
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Quoting allancalderini:
I agree by the Tornado that form in the water in here don`t know the name in English there is a disappear fishermen. Never in my life I want to experience a tornado.
anyone has answer for this?
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Quoting seer2012:
A cat 4 storm hit Hawaii in Sept. 1992 causing severe damage,yet I have never heard of that storm name being retired.(Iniki)Is it because there wasn't a large loss of life involved?
What an infamous year that was, Andrew also struck that same year.
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1144. Tango01
Quoting ScooterXX7:


Category 1...Perhaps less than $5 billion in damage? Three deaths?

Are we going to retire every hurricane that impacts a nearby metro area now? Should be reserved for the notorious, like Andrew, Katrina, Camille, etc.


Why $5 B only? It sounds to me at least double than that (Gustav was about $8B and the effects of Isaac are clearly worst than Gustav's).

What I would suggest to retire (and ASAP) is the SS scale. It is clear that it provides a very inaccurate idea of damaging potential particularly at its lower range. Recent examples are Katrina (cat. 3 which looked more like a cat 5) Ike (cat 2 only!) and now Isaac (cat 1 only). The problem with that I see with the SS scale is precisely its main attribute: the idea of a simple way to convey an idea of the potential damaging effect of a hurricane to non-experts and general public. The problem is that people may say: we survived cat 2 Gustav with little damage 4 years ago so it should be fine with cat 1 Isaac so they decided not to evacuate... So the SS scale becomes quite dangerous. Besides, construction practices from the late 60s when the scale was developed are quite different now so the damaging potential for a given wind speed on a construction 50 years ago may not be the same what can be observed today.
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Quoting allancalderini:
Karl nor Alex were in 2010 nor Emily in 2005.


Nor was Humberto, I doubt Ernesto (maybe, he did quite a number after his second landfall in areas Stan affected and was retired for) or Gordon (he did actually make landfall in the Azores) will be from this year.

Neither was Maria (who made landfall in Newfoundland as well last year), Richard in 2010, Bill in 2009 (again, Newfoundland); Omar, Dolly in 2008. I could go on.

PS: Kirk is the most adorable little hurricane I've seen in years, and Leslie has the potential to be a huge hazard, I'm worried mostly for Bermuda on this one. They haven't seen a significant storm since Fabian.
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A cat 4 storm hit Hawaii in Sept. 1992 causing severe damage,yet I have never heard of that storm name being retired.(Iniki)Is it because there wasn't a large loss of life involved?
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Quoting allancalderini:
Really?LOL how so? we used Emily last year.
Oh duhhh lol, had a brain fart.
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Quoting GTcooliebai:
252 hrs. Nova Scotia is next.


That is a close call for the US and bad news for Canada.
Notice the trough over the Great Lakes, would be a nice cool down.
Member Since: March 16, 2012 Posts: 127 Comments: 7928

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About

Jeff co-founded the Weather Underground in 1995 while working on his Ph.D. He flew with the NOAA Hurricane Hunters from 1986-1990.