Average hurricane season foreseen by CSU, NOAA, and TSR

By: Dr. Jeff Masters , 4:45 PM GMT on June 02, 2009

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A near-average Atlantic hurricane season is on tap for 2009, according to the seasonal hurricane forecast issued June 2 by Dr. Phil Klotzbach and Dr. Bill Gray of Colorado State University (CSU). The CSU team is calling for 11 named storms, 5 hurricanes, and 2 intense hurricanes, and an Accumulated Cyclone Energy (ACE) 88% of average. Between 1950 - 2000, the average season had 10 named storms, 6 hurricanes, and 2 intense hurricanes. But since 1995, the beginning of an active hurricane period in the Atlantic, we've averaged 15 named storms, 8 hurricanes, and 4 intense hurricanes per year. The new forecast is a step down from their April forecast, which called for 12 named storms, 6 hurricanes, and 2 intense hurricanes. The new forecast calls for a near-average chance of a major hurricane hitting the U.S., both along the East Coast (28% chance, 31% chance is average) and the Gulf Coast (28% chance, 30% chance is average). The Caribbean is also forecast to have an average risk of a major hurricane.

The forecasters cited several reasons for an average season:

1) Sea surface temperature (SST) anomalies in the tropical Atlantic are quite cool. In fact, these SST anomalies are at their coolest level since July 1994. Cooler-than-normal waters provide less heat energy for developing hurricanes. In addition, an anomalously cool tropical Atlantic is typically associated with higher sea level pressure values and stronger-than-normal trade winds, indicating a more stable atmosphere with increased levels of vertical wind shear detrimental for hurricanes. Substantial cooling began in November 2008 (Figure 1), primarily due to a stronger than average Bermuda-Azores High that drove strong trade winds. These strong winds increased the mixing of cool waters to the surface from below, and caused increased evaporational cooling.

2) Hurricane activity in the Atlantic is lowest during El Niño years and highest during La Niña or neutral years. This occurs because El Niño conditions bring higher wind shear over the tropical Atlantic. The CSU team expects the current neutral conditions may transition to El Niño conditions (70% chance) by this year's hurricane season. I discussed the possibility of a El Niño conditions developing this year in a blog posted Friday.


Figure 1. Change in Sea Surface Temperature anomaly between November 2008 and 2009. Most of the Atlantic has cooled significantly, relative to normal, over the past 7 months. Image credit: NOAA/ESRL.

Analogue years
The CSU team picked five previous years when atmospheric and oceanic conditions were similar to what we are seeing this year: neutral to slightly warm ENSO conditions, slightly below-average tropical Atlantic SSTs, and above-average far North Atlantic SSTs during April-May. Those five years were 2002, which featured Hurricane Lili that hit Louisiana as a Category 1 storm; 2001, featuring Category 4 storms Michelle, which hit Cuba, and Iris, which hit Belize; 1965, which had Category 3 Betsy that hit New Orleans; 1960, which had two Category 5 hurricanes, Ethyl and Donna; and 1959, which had Category 3 Hurricane Gracie, which hit South Carolina. The mean activity for these five years was 10 named storms, 6 hurricanes, and 2 intense hurricanes, almost the same as the 2009 CSU forecast.

How accurate are the June forecasts?
The June forecasts by the CSU team have historically offered a skill of 20 - 30% higher than a "no-skill" forecast using climatology (Figure 2). This is a decent amount of skill for a seasonal forecast, and these June forecasts can be useful to businesses such as the insurance industry and oil and gas industry that need to make bets on how active the coming hurricane season will be. This year's June forecast uses the same formula as last year's June forecast, which did quite well predicting the 2008 hurricane season (prediction: 15 named storms, 8 hurricanes, 4 intense hurricanes; observed: 16 named storms, 8 hurricanes, 5 intense hurricanes). An Excel spreadsheet of their forecast skill (expressed as a mathematical correlation coefficient) show values from 0.44 to 0.58 for their June forecasts, which is respectable.


Figure 2. Accuracy of long-range forecasts of Atlantic hurricane season activity performed at Colorado State University (CSU) by Dr. Bill Gray's team (colored squares) and Tropical Storm Risk, Inc. (TSR, colored lines). The skill is measured by the Mean Square Skill Score (MSSS), which looks at the error and squares it, then compares the percent improvement the forecast has over a climatological forecast of 10 named storms, 6 hurricanes, and 2 intense hurricanes. TS=Tropical Storms, H=Hurricanes, IH=Intense Hurricanes, ACE=Accumulated Cyclone Energy, NTC=Net Tropical Cyclone Activity. Image credit: TSR.

NOAA's 2009 hurricane season forecast
The National Oceanic and Atmospheric Administration (NOAA), issued its 2009 Atlantic hurricane season forecast on May 21. NOAA anticipates that an average season it most likely, giving a 50% chance of a near-normal season, 25% chance of an above-normal season, and a 25% chance of a below-normal season. They give a 70% chance that there will be 9 - 14 named storms, 4 - 7 hurricanes, 1 - 3 major hurricanes, and an Accumulated Cyclone Energy (ACE) in the 65% - 130% of normal range. The forecasters cited the following main factors that will influence the coming season:

1) We are in an active period of hurricane activity that began in 1995, thanks to a natural decades-long cycle in hurricane activity called the Atlantic Multidecadal Oscillation (AMO).

2) There will either be an El Niño event or neutral conditions in the Equatorial Eastern Pacific. An El Niño event should act to reduce Atlantic hurricane activity. However, our skill at predicting an Niño in late May/early June is poor, so there is high uncertainty about how active the coming hurricane season will be.

3) Cooler-than-average SSTs are currently present in the eastern tropical Atlantic. These cool SSTs are forecast to persist through into August-September-October (ASO). ASO SSTs in the eastern tropical Atlantic have not been below average since 1997. Cooler SSTs in that region are typically associated with a reduction in Atlantic hurricane activity.

Thus, they expect that even though we are in an active hurricane period, the presence of an El Niño or cool SSTs in the eastern Atlantic could easily suppress activity, making a near-average season the most likely possibility. They note that two promising computer models, the NOAA CFS model and the European Center for Medium-Range Weather Forecasts (ECMWF) Global Climate Model System 3, both forecast the possibility of a below-average hurricane season.

2009 Atlantic hurricane season forecast from Tropical Storm Risk, Inc.
The British private forecasting firm Tropical Storm Risk, Inc. (TSR) has joined the ranks of NOAA and Colorado State University in calling for near-average activity. The latest TSR forecast issued June 4 calls for 10.9 named storms, 5.2 hurricanes, 2.2 intense hurricanes, and an Accumulated Cyclone Energy (ACE) 72% of average. The storm numbers are close to the 50-year average of 10 named storms, 6 hurricanes, and 2 intense hurricanes, and are sharp reduction from their April forecast of 15 named storms, 7.8 hurricanes, and 3.6 intense hurricanes. TSR predicts a 50% chance that this season will be in the bottom 1/3 of years historically, and a 40% chance that U.S. landfalling activity will be in the lowest 1/3 of years historically. TSR gives a 32% chance of a near-normal season, and a 17% chance of a below normal season. TSR rates their skill level as 26% above chance at forecasting the number of named storms, 15% skill for hurricanes, and 19% skill for intense hurricanes.

TSR projects that 3.2 named storms will hit the U.S., with 1.3 of these being hurricanes. The averages from the 1950-2008 climatology are 3.2 named storms and 1.5 hurricanes. Their skill in making these April forecasts for U.S. landfalls is 7 - 18% above chance. In the Lesser Antilles Islands of the Caribbean, TSR projects 0.9 named storms, 0.4 of these being hurricanes. Climatology is 1.1 named storms and 0.5 hurricanes.

TSR cites two main factors for their reduced forecast: a large and unexpected cooling of sea surface temperatures in the tropical Atlantic, and warmer SSTs in the Equatorial Eastern Pacific (which might lead to an El Niño event that will bring high wind shear to the Atlantic). TSR expects faster than than normal trade winds from July - September over the Main Development Region (MDR) for hurricanes over the Atlantic (the region between 10° - 20° N from Central America to Africa, including all of the Caribbean). Trade winds are forecast to be 0.83 meters per second (about 1.7 mph) faster than average in this region, which would create less spin for developing storms, and allow the oceans to cool down, due to increased mixing of cold water from the depths and enhanced evaporational cooling. TSR forecasts that SSTs will cool an additional 0.3°C compared to average over the MDR during hurricane season.

Air France crash
The Air France Flight 447 A330 aircraft that disappeared over the mid-Atlantic Ocean yesterday definitely crossed through a thunderstorm complex near the Equator, according to a detailed meteorological analysis by Tim Vasquez. He concludes that "the A330 would have been flying through significant turbulence and thunderstorm activity for about 75 miles (125 km), lasting about 12 minutes of flight time" but that "complexes identical to this one have probably been crossed hundreds of times over the years by other flights without serious incident". See also the excellent CIMSS satellite blog for more images and analysis of the weather during the flight.

Invest 92
NHC is tracking a storm near the Azores Islands (Invest 92L) that is probably the remnants of the core of an extratropical cyclone that closed off some warm air at the center. The system has developed some heavy thunderstorm activity near its center, making this a hybrid storm. However, with ocean temperatures near 62°F (16°C), this storm has little chance of becoming a named subtropical storm.

Jeff Masters

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Reflector site for those at work, which now also includes Weather456, daily updates


AOI #1

AOI #2
Member Since: Posts: Comments:
1261. WxLogic
Quoting Tropicsweatherpr:
This is impressive for being early June.The 8 AM Discussion of wave in Central Atlantic.Will this wave be the trigger for development in the Caribbean?



<
A TROPICAL WAVE IS ALONG 42W/43W S OF 16N MOVING W 10-15 KT.
THIS WAVE IS ASSOCIATED WITH A RATHER HIGHLY AMPLIFIED MAXIMUM
IN DEEP LAYER MOISTURE BASED ON THE TOTAL PRECIPITABLE WATER
PRODUCT FROM CIMSS. SATELLITE IMAGERY INDICATES THAT THE WAVE
CORRESPONDS WITH A LARGE INVERTED-V SIGNATURE IN THE LOW LEVEL
CLOUD FIELD...WITH SATELLITE DERIVED WINDS INDICATING CYCLONIC
CURVATURE IN THE LOW LEVEL FLOW NEAR THIS WAVE. SCATTERED
MODERATE CONVECTION IS FROM 5N-9N BETWEEN 38W-43W. THE DEEP
LAYER MOISTURE ASSOCIATED WITH THE WAVE APPEARS TO BE AT THE
LEADING EDGE OF DRY LOW/MID-LEVEL SAHARAN AIR...WHICH IS FURTHER
ENHANCING THIS CONVECTION AND INCREASING THE POTENTIAL FOR GUSTY
WINDS WITH THE CONVECTION.


I will doubt it... the tropical wave will need to travel ~2600miles to get to the SW Carib where development is forecasted in less than 84 hours... if it's currently moving (fast case scenerio) at 15knots... it will take it close to 150hrs to get there if I'm not mistaking. Unless if it speeds up.
Member Since: Posts: Comments:
Quoting IKE:


LOL....had over 10 inches in May.

Now it's raining again. You should see my yard...lol...or what's left of it....


I feel your pain! Tampa has a 70% chance of rain today. The no name storm dropped over a foot of rain at my house and we've had several more rain events since then. We'll probably add to it today.
Member Since: April 26, 2009 Posts: 3 Comments: 3667
Quoting barryweather:
Didn't the last low pressure system move right over the Mobile/Pensacola area? Jeez...It's like we have bullseye over us.


Better now, than in August and September.
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1258. cg2916
What does the scale on the GFS mean?
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1257. IKE
Quoting CaneWarning:


Does it always rain at your house? It seems like every time you post you have rain!


LOL....had over 10 inches in May.

Now it's raining again. You should see my yard...lol...or what's left of it....
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1256. IKE
Quoting barryweather:
Didn't the last low pressure system move right over the Mobile/Pensacola area? Jeez...It's like we have bullseye over us.


Yup.
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Quoting IKE:


LOL!

You knew I'd be here. Thanks for posting the info while I was sawing a log.....

And I currently have rain and 72 outside my window.


Does it always rain at your house? It seems like every time you post you have rain!
Member Since: April 26, 2009 Posts: 3 Comments: 3667
Quoting TaminFLA:


I have always worried about the kids of Andrew :( I thank God I went to my parents home, and my children were very young- of course they remember what happened afterwards as it was a mess for over a year, but we kinda got right back on the horse...had to....I worked for the government, my husband works for FPL and my childrens father is a police officer so that did't give us much time to sit around.

And your right, NOBODY was worried about this storm. It was a lesson for all.

On a bright note...you seem to be interested in weather now :)


Yes, Andrew is the cause for my interest with the tropics. I never want to be caught unaware again.
Member Since: April 26, 2009 Posts: 3 Comments: 3667
Didn't the last low pressure system move right over the Mobile/Pensacola area? Jeez...It's like we have bullseye over us.
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1252. IKE
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1251. IKE
It is a low. This from the morning discussion out of Mobile,AL....

"AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MOBILE AL
424 AM CDT THU JUN 4 2009

.SHORT TERM (TODAY AND TONIGHT)...SFC ANALYSIS AND IR/WV LOOPS SHOW
A WEAK AREA OF LOW PRESSURE JUST EAST OF MOBILE...MOSTLY A
REFLECTION OF THE MID LEVEL TROUGH SHIFTING EASTWARD ALONG THE AL
AND NWFL BORDER."
Member Since: Posts: Comments:
This is impressive for being early June.The 8 AM Discussion of wave in Central Atlantic.Will this wave be the trigger for development in the Caribbean?



<
A TROPICAL WAVE IS ALONG 42W/43W S OF 16N MOVING W 10-15 KT.
THIS WAVE IS ASSOCIATED WITH A RATHER HIGHLY AMPLIFIED MAXIMUM
IN DEEP LAYER MOISTURE BASED ON THE TOTAL PRECIPITABLE WATER
PRODUCT FROM CIMSS. SATELLITE IMAGERY INDICATES THAT THE WAVE
CORRESPONDS WITH A LARGE INVERTED-V SIGNATURE IN THE LOW LEVEL
CLOUD FIELD...WITH SATELLITE DERIVED WINDS INDICATING CYCLONIC
CURVATURE IN THE LOW LEVEL FLOW NEAR THIS WAVE. SCATTERED
MODERATE CONVECTION IS FROM 5N-9N BETWEEN 38W-43W. THE DEEP
LAYER MOISTURE ASSOCIATED WITH THE WAVE APPEARS TO BE AT THE
LEADING EDGE OF DRY LOW/MID-LEVEL SAHARAN AIR...WHICH IS FURTHER
ENHANCING THIS CONVECTION AND INCREASING THE POTENTIAL FOR GUSTY
WINDS WITH THE CONVECTION. /strong>
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1249. IKE
Check this radar out of Mobile. Looks like a low moving ENE....

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Quoting CycloneOz:
PS: These animations are totally different than in previous years.


Well...not "totally different." I still like using the Jurassic Park theme for these videos. :)
Member Since: Posts: Comments:
1247. IKE
6Z NAM looks further west than the 6Z GFS
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This is the GOES East Infrared Hurricane Sector Animation for July - September 2008.

The new ones I'm working on don't look anything like this! :)
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The caribbean seems to the certain point of moisture next week. The uncertainty lies who is after the Caribbean. Moisture could reach the East coast per some solutions.
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'morning all. :)

Just to let you know, I've begun creating my GOES East Infrared Hurricane Sector animations for this year.

That's right! Animations [plural]!

And as an added bonus, they'll be in hi-def this year, too!

I'll release them on the 1st of each month [unless I'm out there, somewhere...at that time] beginning July 1st.

CycloneOz---

PS: These animations are totally different than in previous years. They're literally gonna knock your socks off! :)
Member Since: Posts: Comments:
1243. IKE
Quoting sporteguy03:
Ike,
00z GFS still develops a low lol. See you at 6z


LOL!

You knew I'd be here. Thanks for posting the info while I was sawing a log.....

And I currently have rain and 72 outside my window.
Member Since: Posts: Comments:
Quoting CaneWarning:


I remember the same thing. I was 11 at the time and I don't remember my parents or anyone else being worried about the storm until the last minute. Even as it was heading towards us everyone thought it wouldn't be so bad. I remember being in the center bathroom and the rest of the house was just gone. I remember my dad opening the door of the bathroom later and saying, "The house is gone." I can still hear the roar of the winds. That's a sound you'll never forget. I remember my family getting lost around the Cutler Ridge area and couldn't figure out how to get home a few days after the storm because everything was so damaged. I remember driving around in our car that had no windows because they were all blown out. Anyway, sorry to ramble...I could go on and on. It's something you'll never forget.


I have always worried about the kids of Andrew :( I thank God I went to my parents home, and my children were very young- of course they remember what happened afterwards as it was a mess for over a year, but we kinda got right back on the horse...had to....I worked for the government, my husband works for FPL and my childrens father is a police officer so that did't give us much time to sit around.

And your right, NOBODY was worried about this storm. It was a lesson for all.

On a bright note...you seem to be interested in weather now :)
Member Since: Posts: Comments:
1241. WxLogic
As IKE has stated... GFS has starting to receive quite a bit of support from CMC, NOGAPS, and ECMWF(being the weakest).

CMC has this system organizing just off the FL E Coast.

NOGAPS has it organizing on the S GOM and entering W FL and seems to be trending stronger with each run.

ECMWF seems to be in between the afformentioned models but not too different from GFS.

GFS of course has been at it for a while (close to a week) and trending towards a NE track in response to a weekness in the Bermuda High later in the period (towards Monday/Tuesday).

These 00Z/06Z runs were interesting... we'll see about the 12Z runs.
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1240. IKE
If the GFS verifies, this may be a track similar to ........

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1239. WxLogic
Good morning guys....
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the 6z gfs is even more aggresive than the 00z.
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1237. IKE
06Z NOGAPS @ 850mb's.
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1236. IKE
It's got company in the 00Z CMC.
Member Since: Posts: Comments:
1235. IKE
Quoting Weather456:
Good morning

The 00Z GFS run has a similiar solution to the 06Z run

Tropical Update


Looks like it's coming nowhere near Florida.
Member Since: Posts: Comments:
Good morning

The 00Z GFS run has a similiar solution to the 06Z run

Tropical Update
Member Since: Posts: Comments:
Quoting CybrTeddy:


Hugo was a Category 5. Jeff Masters even flew into Hugo while it was a Category 5.


Yes, it just wasn't a Category 5 for long - only 6 hours... and that was out in the Atlantic. The Good Doctor definitely picked the wrong moment to fly in!
Member Since: August 23, 2008 Posts: 7 Comments: 5300
000
ABNT20 KNHC 040538
TWOAT
TROPICAL WEATHER OUTLOOK
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
200 AM EDT THU JUN 4 2009

FOR THE NORTH ATLANTIC...CARIBBEAN SEA AND THE GULF OF MEXICO...

TROPICAL CYCLONE FORMATION IS NOT EXPECTED DURING THE NEXT 48 HOURS.

$$
FORECASTER AVILA


Member Since: Posts: Comments:
Quoting KEHCharleston:
Yep... size does matter!
Hugo was not a Cat 5 (except on Wiki and according to some old timers) -- but it was HUGE. As far away as Charlotte, NC (170 miles from landfall) experienced Cat1 hurricane and gusts over 100 mp
Some of the most profound difficulty from the storm, was the human impact on very poor, very rural areas of inland SC


ADDED: Gives me chills thinking about Flying into Hugo - as Jeff Masters did.


Hugo was a Category 5. Jeff Masters even flew into Hugo while it was a Category 5.
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1229. Makoto1
Quoting slickasatick:
there is a 100% chance at least one names storm will form between africa and north america


lol That might be the best prediction I've seen this year.

Seriously though, I agree there's potential for something to happen in the Caribbean.. But it's amazing how quiet June is that we're watching blobs without much chance for the most part. Not like that's a bad thing.
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Member Since: Posts: Comments:
Quoting albert0826:
i just graduated high school.


Congratulations! We had our grad this past weekend. It was really fun and we took lots of pictures although some I would rather be deleted (after party) lol
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Ike,
00z GFS still develops a low lol. See you at 6z
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Hey, all.

I just spent the day in the midst of the weather on the East Coast. Currently I am in Boston, MA, after traversing some pretty hectic weather in Philadelphia this afternoon. In fact, my flight was delayed so long because of the weather there that we actually took off from Philadelphia AFTER we were scheduled to arrive in Boston!

I had with me my trusty Canon, and will post ASAP some of the better shots of the weather I experienced today. Maybe I'll even do a bit of a blog entry on it. . . ;o)
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1221. gator23
Goodnight all! Happy blob watching!
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Quoting albert0826:
i just graduated high school.
Congratulations!

Have Fun and Be safe with the celebrating.

Here comes more rain Florida...

South Florida Water Management District RADAR
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Hi Orca you still here? What about CaneW?
Member Since: September 3, 2007 Posts: 3 Comments: 1519
1217. Skyepony (Mod)
Oss~ Sleep well. My Gauss Meter says all is safe....


But to ponder~ how about since elf makes molecules like air pollution sticky, it removes enough particles from the air to reduce rainfall in intense areas..

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AOI #1

AOI #2

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Congrats..I'm class of '08 and now attend FSU!!
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congtrats!!!!,get your butt in college ASAP,it'll make it easier to make the transition!!!
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i just graduated high school.
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Good evening everyone...Since it is now hurricane season, I have posted a pretty nice contest into my blog!! It features the typical named storms/hurricanes/major hurricanes that we are all familiar with ...and it also has a "predict the landfall location" part. It should be rather fun...and the overall points from the two will be added together to determine a winner at the end of the season. Hope you all enjoy...and feel free to leave me a comment with your predictions or send me some mail. Good Luck!!! =D

Link
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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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