Irene roars into life; may become the season's first hurricane

By: Dr. Jeff Masters , 12:03 AM GMT on August 21, 2011

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Tropical Storm Irene roared into life this evening, transitioning from a tropical wave to a 50 mph tropical storm in just a few short hours. An Air Force hurricane hunter aircraft in the storm was finishing up its mission when it suddenly came across a region with intense thunderstorms and surface winds of 50 mph. The aircraft found that a center of circulation had barely closed off on the southwest edge of this region, though the plane found almost no winds from the west around the circulation center. The 6:10pm EDT center fix found a central pressure of 1007mb, which is quite high for the observed 50 mph winds. Dry air to the north and west is slowing development, as well as moderate wind shear of 10 - 20 knots, as analyzed by the University of Wisconsin CIMSS group. Infrared satellite loops and radar out of Martinique show the storm is poorly organized, with no evidence of spiral bands. The center of Irene is expected to cross over the Caribbean island of Dominica early Sunday morning, but the heaviest thunderstorms lie to the north of the center, and will affect Guadeloupe, Antigua, and St. Kitts and Nevis.


Figure 1. Evening satellite image of Irene.

The computer models have shifted southwards since yesterday, and now take Irene south of Puerto Rico on Monday, and along the south shore of the Dominican Republic on Tuesday. On Wednesday, Irene should pass near or over southern Haiti, Eastern Cuba, and Jamaica. On Wednesday and Thursday, the models agree that a trough of low pressure will dip down over the Eastern U.S., which is likely to turn Irene to the north. The exact timing and strength of this trough varies considerably from model to model, and will be critical in determining where and when Irene will turn to the north. We can expect that Irene will impact Central Cuba, the Bahamas, and the Florida Keys on Thursday, but it is uncertain whether Irene's turn to the north will take the storm into the Gulf of Mexico or not. Irene most reminds me of Tropical Storm Fay of 2008. Fay formed just off the coast of Puerto Rico, and was never quite able to get organized enough to become a hurricane, due to passage over Hispaniola and Cuba. Fay topped out as a strong tropical storm with 70 mph winds, and did over $500 million in damage in the U.S., mostly due to flooding rains in Florida that accumulated to over 25 inches in a few areas. Fay also dumped heavy rains on Hispaniola, triggering flooding that claimed eight lives.


Figure 2. Track of Tropical Storm Fay of 2008.

Irene will be battling dry air and moderate wind shear of 10 - 20 knots through Sunday, and it will take the storm 1 - 3 days to build up an eyewall and intensify into a hurricane. Irene is more of a threat than Tropical Storm Emily of early August was, since Irene has closed off a center farther east than Emily did and has more time to organize before encountering Hispaniola. I don't think passage over Hispaniola will destroy Irene, since it is a fairly large storm, and is likely to be a hurricane by then. However, if Irene follows the NHC forecast, it will have an extended encounter with Hispaniola and Cuba on Tuesday through Wednesday that will probably weaken the storm below hurricane force. Keep in mind that the average error for an official 5-day forecast from NHC for a developed storm is 200 - 250 miles. Irene could easily miss Florida and move up the East Coast and hit North or South Carolina, or pass through the Florida Keys and into Gulf of Mexico, ending up who knows where. Given the uncertainties, this weekend would be a good time to go over your hurricane preparedness if you live anywhere in the Caribbean, Bahamas, or U.S. coast, since Irene could well be paying you a visit as a tropical storm or hurricane sometime in the next week.

Harvey hits Belize
Tropical Storm Harvey made landfall at 2pm EDT on Saturday near Dangriga Town, Belize, as a tropical storm with 60 mph winds. Harvey continues to dump very heavy rains on northern Guatemala, Belize, and portions of Mexico's Yucatan Peninsula as the storm tracks westwards at 12 mph. Dissipation is expected Sunday as the storm pushes inland. Harvey was a small storm, and the strongest winds were confined to a short stretch of coast near where the center came ashore. Winds at Belize City, Belize on Saturday topped out at 15 mph.


Figure 3. Radar image of Harvey taken at 11:30am EDT on Saturday, August 20, 2011, a few hours before landfall in Belize. A small closed eye is visible just south of the offshore islands of Belize. Image credit: Belize National Meteorological Service.

An exceptionally active early part of hurricane season
It's been a strangely hyperactive season for weak storms in the Atlantic so far this year. Tropical Storm Irene is the 9th named storm this year, and its formation date of August 20 ties 2011 with 1936 as the 2nd earliest date for formation of the season's 9th storm. Only 2005 had an earlier date. The first eight storms this year have stayed below hurricane strength, making 2011 the first hurricane season since record keeping began in 1851 to have more than six consecutive tropical storms that did not reach hurricane strength. As I discussed in Friday's post, a major reason for this is the lack of vertical instability over the tropical Atlantic so far this year. We've had a large amount of dry, sinking air over the tropical Atlantic, and the usual amount of dry, dusty air from the Sahara, both helping to keep the atmosphere stable and stop this year's storms from intensifying into hurricanes. Hurricane activity typically ramps up big-time by August 20, with more than 80% of all the hurricanes and 65% of all the tropical storms occurring after that date. At our current pace, 2011 will become the second busiest Atlantic hurricane season on record, with 24 - 27 named storms. There are only 21 names in the list of names for a hurricane season, so we may have to break out the Greek alphabet again in late October this year, as occurred in 2005. Ironically, this was the last time the current set of names was used in the Atlantic, so 16 of this year's 21 names are repeats of 2005. I'm not too happy about seeing another hurricane season challenge the Hurricane Season of 2005 in any way, and let's hope we don't retire another five names this year, like occurred in 2005! With vertical instability much lower this year than in 2005, and that year having already seen one storm (Dennis) retired by this point in the season, I doubt that will happen, though.


Figure 2. The annual cycle of average hurricane frequency in the Atlantic. Historically, about 35% of all the tropical storms and 15% of all the hurricanes will have occurred by August 20.

Invest 98L near the Cape Verde Islands
A tropical wave near Cape Verde Islands off the coast of Africa, Invest 98L, is spreading heavy rains and strong gusty winds to those islands today. So far this morning, top sustained winds measured in the Cape Verde Islands were 23 mph at Mindelo. 98L has a long stretch of ocean to cross before it could affect any land areas. Approximately 70 - 80% of all tropical cyclones that pass this close to the Cape Verde Islands end up curving out to sea and not affecting any other land areas, according to Dr. Bob Hart's excellent historical probability of landfall charts. The latest set of long-range model runs go along with this idea, and I'd be surprised if 98L threatens any land areas.

Jeff Masters

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Quoting zparkie:
Either way it definately looks like a south florida event, Home Depot and Publix are already calling for all employees to report to work, batteries, flashlights, radios, gas cans, plywood, food, ice, water, can goods, everything will be flying off the shelves, and oh god the long lines, the news media will be charged up warning people of an impending disaster, all the weather channel guys are on their way camping out all along the florida coast to stand in the high winds and become famous.



I was at home depot in Miami less than 2hours ago. Nothing but a few plumbers and contractors. Definitely not busy.
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3670. zparkie
just called my doctor, he already ran out of xanax, damn
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3669. zparkie
Either way it definately looks like a south florida event, Home Depot and Publix are already calling for all employees to report to work, batteries, flashlights, radios, gas cans, plywood, food, ice, water, can goods, everything will be flying off the shelves, and oh god the long lines, the news media will be charged up warning people of an impending disaster, all the weather channel guys are on their way camping out all along the florida coast to stand in the high winds and become famous.
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Looks to have reformed to the North putting the center closer to a direct hit on the Leeward Islands including Puerto Rico. 2:00 AM Advisory should show the jog to the North. PR residents will have little time to prepare for tropical storm conditions. Also, the system may approach Hurricane strength Sunday afternoon or evening. Based on this motion storm could pass closer to the NE coast of PR. Unless, I am missing something here. . .
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NEW BLOG!
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This girl needs to get her act together, and do it fast. I am really tired of the "dry air intrusion" that has plagued every single system this season. I really thought I was going to wake up to at least a Cat 1 Hurricane, breaking this incredibly cursed season of 2011.

She needs her strength if she is going to have to hold it together and traverse Hispanola. Perhaps she will miss that island, sparing Haiti. They really don't have the rresources to deal with a strong storm on their doorstep.

It seems pretty clear that Irene has her sights set on the East Coast. Hopefully she will arrive there with a little more to offer than a fart in the wind and a light misting of rain.

This season is unreal.
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Quoting K8eCane:




Im a lot closer to agreeing with you now. Be prepared. You will probly get more rain than us in Wilmington



The funny thing is that this is my first time experiencing a tropical system since I have been living in Oakland, CA all of my life.
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3664. K8eCane
Quoting WeafhermanNimmy:
We are going to get a lot of rain in Greensboro, NC from this system.




Im a lot closer to agreeing with you now. Be prepared. You will probly get more rain than us in Wilmington
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3663. BVI
Wind starting to pick up here in Tortola, British Virgin Islands and our airports are just about to close:
The BVI Airports Authority has advised that all three airports will close at 12:30pm today with an estimated opening time of 10am tomorrow.
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3662. msphar
P451 - Can you repost your chart from 3621

Thx. Mike
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3661. USCGLT
Quoting Autistic2:



I don't want to remember David. I went through David on a USCG High Endurance cutter on a search and rescue mission.
We had a saying.
YOU HAVE TO GO OUT, YOU DON'T HAVE TO COME BACK!.
David berrrr


Which 378 were on? Dallas, Gallitan?
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We are going to get a lot of rain in Greensboro, NC from this system.
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Quoting presslord:
over 700,00 Haitians live like this...many will die...



thank you for showing this. It is important for us to remember this.
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Quoting presslord:
adding insult to injury....next weekend is labor Day...there will be millions of additional souls along the coast...which will drastically complicate evacuations, etc....
ummm, no, next weekend is not Labor Day. Labor Day weekend is two weeks away, Sept. 5.
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3657. MahFL
Seems to be on a track of 280 still.
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Quoting Relix:
Puerto Rico Wuggers! How's stuff going? Here in Levittown some lines are forming in the gas stations. Once has a line of like 20 cars. Very calm winds but cloudy so and cool. I moved my cars around so they aren't affected by any falling trees or anything. No shutters, though that may change if it does strengthen.
Reporting from Ocean Park, P,R:.Link
Very windy since last night, mostly cloud, but very hot, the humidity must be over 100%. No body is in the beach, the streets are unusual empty to be Sunday on a touristic zone. I am ready, i took water. My mom in the eastern central of the Island is ready too.
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3655. 900MB
Irene is just one blow up from hurricane status and that could come at any time with very strong odds that it will happen in next 24 hours.

It would take a lot to keep Irene south of Puerto Rico at this point, and a hurricane warning should be posted.
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Quoting NCHurricane2009:
Aaah...what storm petrol posted is interesting...

visible sat. image says at first this is directly over St. Kitts right now....but the vortex message from recon says that it is centered 27 miles south of that area...

...moreover at the end...it says the circulation is elongated NE to SW by 20 nautical miles...so I guess the center I see in the visible is the NE extent of the elongated circulation spotted by recon....


Corrrect.....The Circ over St Kitts is mid level. Its also has had a northward component to it.
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3653. P451
Quoting PcolaDan:
You guys can stay here if you want, but I'm going to the new blog. :|


Screw the new blog! I just posted a whole bunch of crap.

I'm staying here!


...dammit now I have to spam all that useless crap I just posted on the new blog.

Member Since: December 16, 2007 Posts: 7 Comments: 10202
NEW BLOG
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Current Weather Conditions:
Golden Rock, Saint Kitts and Nevis
Link

10 AM (14) Aug 21 78 (26) 78 (26) 29.59 (1002) S 9 light rain
9 AM (13) Aug 21 77 (25) 75 (24) 29.74 (1007) ENE 9 rain showers
8 AM (12) Aug 21 75 (24) 75 (24) 29.77 (1008) NE 13 heavy rain
7 AM (11) Aug 21 77 (25) 75 (24) 29.94 (1014) NE 16 rain
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Quoting NCHurricane2009:
http://www.ssd.noaa.gov/goes/flt/t2/vis-l.jpg

Irene DEAD CENTER over St. Kitts island area in that image....I think the current positioning of Irene is still a very slight amount too far south this morning...


Been saying it all morning...but thin surface center is 30 forty miles south. Mid over and just west of St Kitts
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3649. P451
Quoting NCHurricane2009:


I think the vortex message recently posted on Irene from recon tells us a lot...

You and I are seeing the center over St. Kitts...which indeed is further north of forecast points...and the center seen by recon wind direction is elongated SW to NE due south of St. Kitts...so at the very surface the circulation perhaps has been and continues to be elongated...

...my guess though is when this get circular instead of elgonated...it will want to center itself further north into the convection....


I think you're right.

The core is broad and ragged so they are merely sampling the lowest pressure. It may not be a pinpoint center they are putting out.

As we saw last night and would probably see today - as the core tightened up the center got pulled further under the convection ---- and the northern solution would probably play out if this happens.

Even with their vortex messages this has a SE PR coastline landfall written all over it --- unless the center is wobbling.
Member Since: December 16, 2007 Posts: 7 Comments: 10202
Having been on a couple of cruises to Bahamas and Mexico, I know that the ocean is full of cruise ships, each one carrying at least 2000 people. I am curious to know if cruise lines intend to brave the storm. The show must go on?
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You guys can stay here if you want, but I'm going to the new blog. :|
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3646. P451
Quoting liljade:
Is there any chance Irene could get in the western GOM?Texas really,really needs the rain!


Looking very doubtful this morning.

This is a Florida storm and perhaps an East Coast US storm given what we are seeing this morning in terms of motion and latitude.

Member Since: December 16, 2007 Posts: 7 Comments: 10202
Quoting Relix:
St Kitts: 10 AM (14) Aug 21 78 (26) 78 (26) 29.59 (1002) S 9 light rain

1002MB Pressure there.


on one of the HH's barbs?
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Quoting P451:
North of 17N, north of the forecast points. This trend started last night and continues. You can't rule out a PR landfall with this setup.


I think the vortex message recently posted on Irene from recon tells us a lot...

You and I are seeing the center over St. Kitts...which indeed is further north of forecast points...and the center seen by recon wind direction is elongated SW to NE due south of St. Kitts...so at the very surface the circulation perhaps has been and continues to be elongated...

...my guess though is when this get circular instead of elgonated...it will want to center itself further north into the convection....
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NEW BLOG
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Quoting presslord:
adding insult to injury....next weekend is labor Day...there will be millions of additional souls along the coast...which will drastically complicate evacuations, etc....


Needs to be repeated.
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3640. P451
PR = Landfall if the center is not wobbling as they plot fixes.






Member Since: December 16, 2007 Posts: 7 Comments: 10202
Quoting presslord:
adding insult to injury....next weekend is labor Day...there will be millions of additional souls along the coast...which will drastically complicate evacuations, etc....


Are you in a time warp, or is the DeLorean's flux capacitor on the fritz again? Labor Day is Sept 5 it's August 21 Marty! That means you still have time to fix the fux capacitor before Irene comes to Florida!
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Quoting MiamiHurricanes09:
000
URNT12 KNHC 211426
VORTEX DATA MESSAGE AL092011
A. 21/14:00:00Z
B. 16 deg 55 min N
062 deg 48 min W
C. 850 mb 1472 m
D. 46 kt
E. 046 deg 42 nm
F. 123 deg 53 kt
G. 046 deg 80 nm
H. 1007 mb
I. 15 C / 1523 m
J. 17 C / 1524 m
K. NA / NA
L. NA
M. NA
N. 1345 / 08
O. 0.02 / 10 nm
P. AF300 0209A IRENE OB 08
MAX FL WIND 53 KT NE QUAD 13:34:30Z
20NM L/V CENTER ELONGATED NE TO SW
;

Don't tell me this is going to be another Emily. Both 50mph with a disorganized center.
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Looks like the wind shear of 10-20kts from the southwest continues to keep Irene a lopsided storm. It should also keep Irene on a 280-285° heading.

If she makes it north of Hispaniola all bets are off and somewhere along the East Coast will get socked. That weakness to the north is just strong enough to pull her in that direction but just weak enough so that it doesn't grab her up and send her off.

This is going to be a huge rain-maker for the Eastern States. Stacked low over Hudson Bay next weekend will force a strong jet stream response over New England and the Canadian Maritimes which will further aid in lift over the Mid-Atlantic/Northeast. Combined with a front dropping in the stage will be set for training pre activity before the storm and the rain from the storm itself. Not looking good.
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Quoting TropicalAnalystwx13:


The National Hurricane Center currently has the system passing JUST south of Puerto Rico during the pre-dawn hours of tomorrow morning.



which is worse. thank god its not a stronger storm... even tho it will get stronger, we wont see a charley here
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Irene


96W



Which looks better.
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Quoting Vero1:


I got "Labor Day" as two weeks away ... Sept 5


Oh man! You're right!!!! My bad.....I lost a whole week.....guess it happens in old age...
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3633. Relix
St Kitts: 10 AM (14) Aug 21 78 (26) 78 (26) 29.59 (1002) S 9 light rain

1002MB Pressure there.
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Quoting weathercuco:


right through Sabana Grande where i live :(
Agree, I think that the center will wobble inland, historically is what had happened when they get within 20 to 30 miles from the coast, don't know the reason why, maybe is topography or a weakness in the ridge in the area; I'm not an expert, just and experienced old falcon, living in this wonderful Island all my life, "cuidense mis hijos". ;).
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NEW BLOG
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New blog up from Dr M
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Quoting P451:
North of 17N, north of the forecast points. This trend started last night and continues. You can't rule out a PR landfall with this setup.



If this continues she could come in on the southern coast of PR and exit the northern coast of DR and head north of Haiti - intensify - and target Florida as a major.

Note, I said COULD, I have not put much thought into it.

All you can do is look at imagery and that is what it is showing.

While steering currents would lead you to believe she should bend a little more westward with time that's not quite how they work or are to be interpreted. These aren't roads and the storm is not a car on a road.

990-999mb storm




970-989mb storm




A stronger system goes further north.
Last vortex at 16.8 and the storm is really only at 45 mph now....but they will leave it at 50. we shall see the update in a few....
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3628. Walshy
Quoting presslord:
adding insult to injury....next weekend is labor Day...there will be millions of additional souls along the coast...which will drastically complicate evacuations, etc....


Member Since: May 17, 2009 Posts: 2 Comments: 904
3627. Vero1
Quoting presslord:
adding insult to injury....next weekend is labor Day...there will be millions of additional souls along the coast...which will drastically complicate evacuations, etc....


I got "Labor Day" as two weeks away ... Sept 5
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Quoting WeatherNerdPR:
Seems like it's gonna clip SW PR...
I sure hope so and then run the whole length of Hisp. and meets the same fate as emily
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New Blog
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Quoting Relix:
Puerto Rico Wuggers! How's stuff going? Here in Levittown some lines are forming in the gas stations. Once has a line of like 20 cars. Very calm winds but cloudy so and cool. I moved my cars around so they aren't affected by any falling trees or anything. No shutters, though that may change if it does strengthen.


The National Hurricane Center currently has the system passing JUST south of Puerto Rico during the pre-dawn hours of tomorrow morning.

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3623. ncstorm
Quoting Bluestorm5:
You know it could get ugly for USA when Allan is saying MAJOR hurricane toward SE USA as one of many possible paths.


I like reading his forecasts because he isnt biased as to NC..he has never said this storm was def coming to NC..he always put all the options in his forecast and that makes a good meterologist
Member Since: August 19, 2006 Posts: 13 Comments: 16039
Aaah...what storm petrol posted is interesting...

visible sat. image says at first this is directly over St. Kitts right now....but the vortex message from recon says that it is centered 27 miles south of that area...

...moreover at the end...it says the circulation is elongated NE to SW by 20 nautical miles...so I guess the center I see in the visible is the NE extent of the elongated circulation spotted by recon....
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3621. P451
North of 17N, north of the forecast points. This trend started last night and continues. You can't rule out a PR landfall with this setup.



If this continues she could come in on the southern coast of PR and exit the northern coast of DR and head north of Haiti - intensify - and target Florida as a major.

Note, I said COULD, I have not put much thought into it.

All you can do is look at imagery and that is what it is showing.

While steering currents would lead you to believe she should bend a little more westward with time that's not quite how they work or are to be interpreted. These aren't roads and the storm is not a car on a road.

990-999mb storm




970-989mb storm




A stronger system goes further north.
Member Since: December 16, 2007 Posts: 7 Comments: 10202

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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.