CSU predicts a very active hurricane season: 16 storms, 9 hurricanes

By: Dr. Jeff Masters , 4:30 PM GMT on June 01, 2011

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A very active Atlantic hurricane season is on tap for 2011, according to the seasonal hurricane forecast issued June 1 by Dr. Phil Klotzbach and Dr. Bill Gray of Colorado State University (CSU). The CSU team is calling for 16 named storms, 9 hurricanes, and 5 intense hurricanes, and an Accumulated Cyclone Energy (ACE) 166% 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 14 named storms, 8 hurricanes, and 4 intense hurricanes per year. The new forecast is identical to their April forecast. The forecast calls for a much above-average chance of a major hurricane hitting the U.S., both along the East Coast (48% chance, 31% chance is average) and the Gulf Coast (47% chance, 30% chance is average). The risk of a major hurricane in the Caribbean is also high, at 61% (42% is average.)

The forecasters cited four main reasons for an active season:

1) Neutral to weak La Niña conditions are expected during the most active portion of this year's hurricane season (August-October). This should lead to average to below average levels of vertical wind shear.

2) Above average May sea surface temperatures in the tropical Atlantic.

3) Below average surface pressures during May in the tropical Atlantic.

4) We are in the midst of a multi-decadal era of major hurricane activity, which began in 1995. Major hurricanes cause 80-85 percent of normalized hurricane damage.

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 weak La Niña conditions in the equatorial Eastern Pacific, and above-average tropical Atlantic and far north Atlantic SSTs during April - May. Those five years were 2008, which featured Hurricane Ike and Hurricane Gustav; 1996, which had two hurricanes that hit North Carolina, Fran and Bertha; 1989, which featured Category 5 Hurricane Hugo; 1981, a very average year with 12 named storms, 7 hurricanes, and 3 intense hurricanes; and 1951, a year that featured 6 major hurricanes. The mean activity for these five years was 12 named storms, 8 hurricanes, and 4 intense hurricanes.

How accurate are the June forecasts?
The June forecasts by the CSU team between 1998 and 2009 had a skill 19% - 30% higher than a "no-skill" climatology forecast for number of named storms, number of hurricanes, and the ACE index (Figure 1). 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. Unfortunately, the CSU June 1 forecasts do poorly at forecasting the number of major hurricanes (only 3% skill), and major hurricanes cause 80% - 85% of all hurricane damage (normalized to current population and wealth levels.) This year's June forecast uses a brand new formula never tried before, so there is no way to evaluate its performance. An Excel spreadsheet of their forecast skill (expressed as a mathematical correlation coefficient) show values from 0.41 to 0.62 for their June forecasts made between 1984 and 2010, which is respectable.


Figure 1. Comparison of the percent improvement over climatology for May and August seasonal hurricane forecasts for the Atlantic from NOAA, CSU and TSR from 1999-2009 (May) and 1998-2009 (August), using the Mean Squared Error. Image credit: Verification of 12 years of NOAA seasonal hurricane forecasts, National Hurricane Center.


Figure 2. Comparison of the percent improvement in mean square error over climatology for seasonal hurricane forecasts for the Atlantic from NOAA, CSU and TSR from 2001-2010, using the Mean Square Skill Score (MSSS). The figure shows the results using two different climatologies: a fixed 50-year (1950 - 1999) climatology, and a 2001 - 2010 climatology. Skill is poor for forecasts issued in December and April, moderate for June forecasts, and good for August forecasts. Image credit: Tropical Storm Risk, Inc.

TSR predicts 25% more activity than normal
Expect the Atlantic hurricane season to be about 25% more active than usual, the British private forecasting firm Tropical Storm Risk, Inc. (TSR) said in their pre-season forecast issued on May 24. TSR calls for 14.2 named storms, 7.6 hurricanes, 3.6 intense hurricanes, and an Accumulated Cyclone Energy (ACE) of 124, which is 22% above average. Their May 24 forecast numbers are very close to their previous forecast issued in April. TSR predicts a moderate 55% chance that activity will rank in the top 1/3 of years historically, and a 59% chance that U.S. landfalling activity will be above average. TSR rates their skill level as 16-25% higher than a "no-skill" forecast made using climatology, though an independent assessment by the National Hurricane Center (Figure 1) gives them somewhat lower skill numbers.

TSR projects that 4.4 named storms will hit the U.S., with 1.9 of these being hurricanes. The averages from the 1950-2010 climatology are 3.1 named storms and 1.5 hurricanes. They rate their skill at making these June forecasts for U.S. landfalls at 7 - 11% higher than a "no-skill" forecast made using climatology. In the Lesser Antilles Islands of the Caribbean, TSR projects 1.3 named storms, 0.6 of these being hurricanes. Climatology is 1.1 named storms and 0.5 hurricanes.

TSR cites two main factors for their forecast of an active season:

1) Their model predicts that sea surface temperatures will be 0.11°C warmer than average in August and September over the Main Development Region (MDR) for Atlantic hurricanes. They define this as the area between 10°N and 20°N, between the coast of Africa and Lesser Antilles Islands (20°W and 60°W). It is called the Main Development Region because virtually all African waves originate in this region. These African waves account for 85% of all Atlantic major hurricanes and 60% of all named storms. When SSTs in the MDR are much above average during hurricane season, a very active season typically results (if there is no El Niño event present.)

2) Their model predicts slower than normal trade winds in August and September over the Main Development Region (MDR). Trade winds are forecast to be 0.19 meters per second (about 0.4 mph) slower than average. This would create more spin for developing storms, and allow the oceans to warm up, due to reduced mixing of cold water from the depths and lower evaporational cooling.

FSU predicts a very active hurricane season: 17 named storms
The Florida State University (FSU) Center for Ocean-Atmospheric Prediction Studies (COAPS) issued their third annual Atlantic hurricane season forecast today. This year's forecast calls for a 70% probability of 14-20 named storms and 8-10 hurricanes. The mean forecast is for 17 named storms, 9 hurricanes, and an accumulated cyclone energy (ACE) of 163. They cite warm tropical North Atlantic sea surface temperatures, a weakening of La Niña conditions, and the ongoing positive phase of the Atlantic Multi-decadal Oscillation as the major factors influencing their forecast.

Other seasonal forecasts
The UK Met Office's Glosea4 model is predicting a moderately more active season than normal, with 13 named storms and a ACE index of 151. The Cuba Institute of Meteorology is calling for 13 named storms and 7 hurricanes. NOAA predicts 15 named storms, 8 hurricanes, and 4.5 intense hurricanes. Pennsylvania State University predicts 16 named storms.

A surprise tropical disturbance for Florida
The Atlantic hurricane season is officially underway, and Mother Nature appears to be taking her cue from the calendar, as we have a surprise storm off the coast of Florida that is a threat to develop into a tropical depression later this week, after it crosses Florida into the Gulf of Mexico. An cluster of thunderstorms called a Mesoscale Convective System (MCS) pushed across southern New England early yesterday, emerged over the ocean, and rotated clockwise towards Florida, steered by a large high pressure system centered over Kentucky. The center of the disturbance stayed over the warm waters of the Gulf Stream, a region of low pressure developed, and intense thunderstorms began to build yesterday afternoon. Early this morning, the National Hurricane Center (NHC) designated the disturbance Invest 93L, and gave it a 10% chance of developing into a tropical depression. At 8am EDT, they upped those chances to 30%. Invest 93L is becoming increasingly organized, with Melbourne, Florida radar showing the beginnings of some rotation, with a solid band of heavy rain on the southwest side of the disturbance. The pressure and winds have leveled out at Buoy 41012, 40 nm ENE of St. Augustine, Florida. Winds peaked at 19 mph, gusting to 22 mph, at 10:50am EDT. Satellite imagery shows a small but intensifying region of thunderstorms. Sea surface temperatures (SSTs) are about 26°C (79°F) off the east coast of Florida, which is just warm enough to support formation of a tropical depression, and about 0.5°C above average. Wind shear is a low 5 - 10 knots, and it is likely that 93L will continue intensifying until it makes landfall over Central Florida this afternoon. A 50-mile wide swath of Florida from Daytona Beach to just north of Tampa can expect 1 - 3 inches of rain from 93L as it tracks over the state this afternoon and tonight. A Windsat pass this morning did not show a closed circulation, and I doubt 93L has enough time to develop into a tropical depression before landfall in Florida. The coast between Daytona Beach and Cocoa Beach could see wind gusts of 25 - 35 mph this afternoon, though.


Figure 3. Afternoon radar image of 93L from the Melbourne, Florida radar.

Fate of 93L once in the Gulf of Mexico
Since 93L is expected to continue its rapid west-southwest motion at 15 - 20 mph through Thursday, it will cross the Florida Peninsula in about 12 hours and emerge over the Gulf of Mexico early Thursday morning. It is possible that the passage over Florida will greatly disrupt 93L, since it is such a small system. I give a 40% chance that the storm will see its peak strength this afternoon, and not significantly regenerate over the Gulf of Mexico. However, the latest SHIPS model forecast predicts that wind shear will remain low to moderate, 5 - 15 knots, as 93L moves westwards over the Gulf of Mexico Thursday and Friday. SSTs in the Gulf are about 27°C (81°F), 0.5 - 1.0°C above average, and it is possible that 93L could gain enough strength to become Tropical Depression One as it crosses the Gulf. Since 93L will be moving parallel to the coast a short distance offshore, it is difficult to predict where the storm might make a second landfall, since a slight change in heading will make a large difference in landfall location. I don't expect widespread heavy rains from 93L along the Gulf Coast, since the storm is so small, but some locations close to the coast could receive 2 - 4 inches as 93L brushes by. Heavier rains are possible at the eventual landfall location. Since 93L is so small, the computer models are having trouble seeing the system, and are not very helpful forecasting the behavior of the storm over the Gulf of Mexico. The Hurricane Hunters are on call to fly into 93L Thursday afternoon at 2pm EDT, if necessary.

Central Caribbean disturbance
Moisture and heavy thunderstorm activity continues to slowly increase in the region between Central America and Jamaica, and wind shear is falling. With wind shear now 20 - 30 knots, we can expect this disturbance to show increased organization today, and recent satellite images show the beginnings of a surface circulation trying to get going about 100 miles off the coast of Northeast Nicaragua. All of the computer models predict that an area of low pressure will form in this region by Thursday, and this low will have the potential to develop into a tropical depression late this week or early next week. A surge of moisture accompanying a tropical wave currently south of Hispaniola may aid development when the wave arrives in the Western Caribbean on Thursday. Water temperatures in the Central Caribbean are about 1°C above average, 29°C, which is plenty warm enough to support development of a tropical storm. Residents of Jamaica, Cuba, the Cayman Islands, Haiti, Honduras, and Nicaragua should anticipate the possibility that heavy rains of 2 - 4 inches may affect them Thursday through Saturday this week.


Figure 4. Satellite image of the Central Caribbean disturbance.

Catch my intro to the 2011 hurricane season on Internet radio
I'll be discussing the coming hurricane season on our Internet radio show, the Daily Downpour, tomorrow (Thursday) at 4:30pm EDT. Fellow wunderground meteorologists Shaun Tanner and Tim Roche will be hosting the show. We'll talk about the latest model runs, hurricane research, modeling accuracy, and hurricane climatology, and answer any questions listeners email in or call in. The email address to ask questions is broadcast@wunderground.com. Welcome to the hurricane season of 2011!

Jeff Masters

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It is the MCV that is on the east coast of Florida, upper atmosphere has broken into 2x 200mb anti-cyclones. 93L now has its own anti-cyclone which is being aided by the ULL to the south. Both are becoming detached as the LLC enters the gulf, and current direction is W/WSW.
Member Since: July 5, 2010 Posts: 0 Comments: 1347
Just got back in, 93L look pretty healthy, started firing a lot of new convection as soon as the edge reached the GOM. Looks like it could still have a shot at developing. Expect to see this back to 30% or so at 8pm EDT.
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Quoting RitaEvac:


Blob has really organized since it's reemerged off Florida.
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Quoting JRRP:
increible que no sea INVEST

Es cuestion de tiempo que 94L va a ser realidad.

Is a matter of time,that 94L will be tagged.
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It's been raining all day across Jamaica
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cmc makes carribean system HUGE
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Plan of the Day

000
NOUS42 KNHC 011515
WEATHER RECONNAISSANCE FLIGHTS
CARCAH, NATIONAL HURRICANE CENTER, MIAMI, FL.
1115 AM EDT WED 01 JUNE 2011
SUBJECT: TROPICAL STORM STORM PLAN OF THE DAY (TSPOD)
VALID 02/1100Z TO 03/1100Z JUNE 2011
WSPOD NUMBER.....11-001

I. ATLANTIC REQUIREMENTS
1. SUSPECT AREA -- GULF OF MEXICO
FLIGHT ONE -- TEAL 70 FLIGHT TWO -- TEAL 71
A. 02/1800Z A. 03/1200Z
B. AFXXX 01AAA INVEST B. AFXXX 0201A CYCLONE
C. 02/1700Z C. 03/1000Z
D. 28.0N 87.0W D. 28.0N 94.0W
E. 02/1730Z TO 02/2200Z E. 03/1100Z TO 03/1600Z
F. SFC TO 10,000 FT. F. SFC TO 10,000 FT.

2. SUCCEEDING DAY OUTLOOK.....NEGATIVE.

II. PACIFIC REQUIREMENTS
1. NEGATIVE RECONNAISSANCE REQUIREMENTS
2. OUTLOOK FOR SUCCEEDING DAY.....NEGATIVE.

NOTE: THIS IS THE FIRST OF A DAILY MESSAGE WHICH WILL
BE TRANSMITTED THROUGHOUT THE HURRICANE SEASON.
JWP

Member Since: July 3, 2005 Posts: 426 Comments: 129089
687. JRRP
heavy rains in Santo Domingo
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Quoting aquak9:
Am I the only one who thinks the LLC is still over land? I mean yeah, there's a lotta convection just hitting the gulf right now, but looking at RGB, esp on zoom...I really think it's kinda de-coupled, and that's just mid- and upper-level that's hitting the GOM right now.

Still feel like LLC is over land.


From what I understand by looking at radar that could be the case - though also judging by the lack of W winds I've been able to find in Florida I think 93L no longer has a LLC and the turning we're seeing is associated with a vigorous MLC that could translate quickly down to the surface in that blowup of convection.
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685. HadesGodWyvern (Mod)
Invest 201193L Infrared radar

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Quoting JRRP:
increible que no sea INVEST

va a ser, solo dale un poco de tiempo probablamente menos de 2 dias
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Quoting aquak9:
I ain't downcasting nothing, Ike. But that cake ain't ready to come outta the oven yet.

That horse ain't left the barn yet.

That's dog's still layin' on the porch.

And that LLC's still over land. :)


I don't think so...
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Quoting aquak9:
I ain't downcasting nothing, Ike. But that cake ain't ready to come outta the oven yet.

That horse ain't left the barn yet.

That's dog's still layin' on the porch.

And that LLC's still over land. :)


Whatever low level center we have is weak. However, that will make it vulnerable to large shifts in position which could help it move under the convection. Who knows, though.
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680. IKE
Quoting aquak9:
I ain't downcasting nothing, Ike. But that cake ain't ready to come outta the oven yet.

That horse ain't left the barn yet.

That's dog's still layin' on the porch.

And that LLC's still over land. :)
LOL!



Member Since: June 9, 2005 Posts: 23 Comments: 37858
LLC shows up clearly on radar.
Member Since: July 5, 2010 Posts: 0 Comments: 1347
Quoting aquak9:
Am I the only one who thinks the LLC is still over land? I mean yeah, there's a lotta convection just hitting the gulf right now, but looking at RGB, esp on zoom...I really think it's kinda de-coupled, and that's just mid- and upper-level that's hitting the GOM right now.

Still feel like LLC is over land.
here is a tune for ya

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Quoting TropicalAnalystwx13:
It's organizing.



Lord help us- next thing ya know, it'll be forming a union and going on strike.
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675. JRRP
increible que no sea INVEST
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I ain't downcasting nothing, Ike. But that cake ain't ready to come outta the oven yet.

That horse ain't left the barn yet.

That's dog's still layin' on the porch.

And that LLC's still over land. :)
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It's organizing.

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Quoting gulfscout:
Any guess what color 93L will be the NHC updates?

I'm thinking it's gonna stay at 20% (Yellow).
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Quoting Thunderfoot:


We need the rain!


Agreed, just dont want no major
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Quoting aquak9:
Am I the only one who thinks the LLC is still over land? I mean yeah, there's a lotta convection just hitting the gulf right now, but looking at RGB, esp on zoom...I really think it's kinda de-coupled, and that's just mid- and upper-level that's hitting the GOM right now.

Still feel like LLC is over land.


Would need to look at surface obs. The old mid-level circulation is spinning off to the NW and dissipating over NE Florida. It looked to me like the low level center was just moving offshore just north of Tampa and just east of the main blob.
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668. IKE
We need you 93L. I'll buy you a steak dinner if you'll cruise up this way.....

thanks....

IKE

$$$


Member Since: June 9, 2005 Posts: 23 Comments: 37858
WBZ Boston just showed tower cam video of tornado in Springfield, MA, crossing the river a few minutes ago. That is the most amazing up-close video of a tornado I've ever seen, with the water and trees along the edge lifting up into the sky.
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good news since the market is crashing, oil is down

WTI Crude Oil
$99.64 ▼3.06
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Quoting duajones78413:



why would we want it to coast into Texas?


We need the rain!
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93L most likely going to hit the tip of the loop current, intensify to near cat 1 strength; and then move towards Mexico/Texas.
Member Since: July 5, 2010 Posts: 0 Comments: 1347
Quoting eyestalker:

Yaller.


or Punurple lol
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Quoting gulfscout:
Any guess what color 93L will be the NHC updates?


Probably no higher than 30%. Still has a ways to go before it can be declared a depression. The NHC likes to see convection persist a while. Still not very sure about any sort of closed circulation either.
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93L has been a blessing. Let's hope it continues to do its good work by dropping rain in places that need it badly.
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Quoting gulfscout:
Any guess what color 93L will be the NHC updates?


Yellow.
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Quoting TropicalAnalystwx13:


How?


1. Popped up out of nowhere
2. Crossed Florida
3. Similar conditions in the GOM

That's about all I can think of right now.
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658. Skyepony (Mod)
Quoting HimacaneBrees:
Will 93L hit the brakes and slow down any? Or will it keep booking it, hell bent for wherever across the Gulf?


I think it will keep up a fairly good clip. Be in TX in two days or so. The High over KY-MS is still there..it's kinda done a big circle around it.
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Quoting gulfscout:
Any guess what color 93L will be the NHC updates?


I'm thinking they are going to keep it at 20% or downgrade it to 10% or less seeing as they want to see how well it does in the GOM.

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Quoting gulfscout:
Any guess what color 93L will be the NHC updates?

Yaller.
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655. IKE

Quoting aquak9:
Am I the only one who thinks the LLC is still over land? I mean yeah, there's a lotta convection just hitting the gulf right now, but looking at RGB, esp on zoom...I really think it's kinda de-coupled, and that's just mid- and upper-level that's hitting the GOM right now.

Still feel like LLC is over land.
Downcaster!!!!
Member Since: June 9, 2005 Posts: 23 Comments: 37858
Member Since: Posts: Comments:
Am I the only one who thinks the LLC is still over land? I mean yeah, there's a lotta convection just hitting the gulf right now, but looking at RGB, esp on zoom...I really think it's kinda de-coupled, and that's just mid- and upper-level that's hitting the GOM right now.

Still feel like LLC is over land.
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Any guess what color 93L will be the NHC updates?
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Quoting Chicklit:
This is good alfabob imho as long as it doesn't end up in LA where they already have more water than they want.


Well, Louisiana is kind of in a lose-lose situation. They need the rain outside of the river drainage areas. The drought is severe to extreme for those areas.
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Got Milk?

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649. IKE

Quoting weathermanwannabe:


102 here in Tally right now with cloudy skies from 93L's circulation attempt.....I hate it this hot and in early June............Jeeeesh.
It is hot.



Quoting sammywammybamy:


The Miami Heat?
Fixing to win the championship.
Member Since: June 9, 2005 Posts: 23 Comments: 37858
Quoting cyclonekid:
93L kinda reminds me of TD 5 last year.



How?
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Quoting mossyhead:
Het index in Crestview is 106f degrees


Some crazy June 1 temps today for sure. Current heat index in Fort Walton Beach is 103, guess I won't be mowing the yard tonight!
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Quoting Chicklit:


yet it is over water and has some organization.
interesting to say the least.
let's hope it winds up coasting into Texas.



why would we want it to coast into Texas?
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645. srada
Quoting reedzone:


Henry is on top of it! I've been following his posts on the tornado.
Link


thanks reed..they live in worcester, very worried about them..
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93L kinda reminds me of TD 5 last year.

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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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