July Atlantic hurricane outlook

By: Dr. Jeff Masters , 12:55 PM GMT on July 13, 2012

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It's mid-July, and we have yet to see a named storm form in the Atlantic this month. The computer models are not predicting any development through at least July 20, and if we make it all the way to the end of the month without a named storm forming, it will be the first July since 2009 without a named storm. Since the current active hurricane period began in 1995, 13 of 17 years (76%) have had a named storm form during July. The busiest July occurred in 2005, when five named storms and two major hurricanes formed. These included Hurricane Dennis and Hurricane Emily--the strongest hurricanes ever observed so early in the season. Only eight major hurricanes have formed in July since record keeping began in 1851. As seen in Figure 1, most of the last half of July activity occurs in the Gulf of Mexico and waters off the Southeast U.S. coast. These type of storms form when a cold front moves off the U.S. coast and stalls out, with the old frontal boundary serving as a focal point for development of a tropical disturbance (as happened for Alberto, Beryl, Chris, and Debby in 2012.) There will be at least two cold fronts moving off the U.S. Mid-Atlantic coast over the next two weeks. The first of these fronts will push offshore around July 20, and we will need to watch the waters offshore of North Carolina for development then. Formation potential will be aided by ocean temperatures that are about 0.7°C (1°F) above average along the U.S. East Coast.


Figure 1. Tracks of all tropical storms and hurricanes 1851 - 2006 that formed July 16-31. The U.S. coast from North to Texas are the preferred strike locations. Only a few storms have formed in the tropical Atlantic and Caribbean in July. Wind shear is typically too high and SSTs too cool in July to allow African waves in the Caribbean and tropical Atlantic to develop into tropical storms. However, a few long-track "Cape Verdes" hurricanes have occurred in July, spawned by tropical waves that came off the coast of Africa. African tropical waves serve as the instigators of about 85% of all major hurricanes.


Figure 2. The seasonal distribution of Atlantic hurricane activity shows that July typically has low activity. Image credit: NHC.

Sea Surface Temperatures: slightly above average
The departure of Sea Surface Temperatures (SST) from average over the tropical Atlantic between Africa and Central America was about 0.3°C above average during June (Figure 3.) This figure has not changed much over the first two weeks of July. These temperatures are not warm enough to appreciably affect the odds of a July named storm or hurricane. The strength of the Azores-Bermuda high has been near average over the past two weeks, driving near-average trade winds. The latest 2-week run of the GFS model predicts continued average-strength trade winds through late-July, so SSTs should remain about 0.3°C above average during this period, due to average amounts of cold water mixing up from below due to the wind action on the water.


Figure 3. Sea Surface Temperature (SST) departure from average for July 12, 2012. SSTs were 0.3°C above average over the tropical Atlantic's Main Development region for hurricanes, from Africa to Central America between 10° and 20° North Latitude. Note the large region of above average SSTs along the Equatorial Pacific off the coast of South America, the hallmark of a developing El Niño episode. Image credit: NOAA/NESDIS

El Niño on the way?
For two consecutive weeks, ocean temperatures 0.5 - 0.6°C above average have been present in the tropical Eastern Pacific, which is right at the threshold for a weak El Niño episode. NOAA's Climate Prediction Center has issued an El Niño Watch, and gives a 61% chance that El Niño conditions will be present during the August - September - October peak of the Atlantic hurricane season. The likely development of a full-fledged El Niño episode means that Atlantic hurricane activity will probably be suppressed in 2012, due to the strong upper-level winds and high wind shear these events typically bring to the tropical Atlantic.


Figure 4. Sea Surface Temperature (SST) departure from average for the the equatorial Eastern Pacific (the area 5°N - 5°S, 120°W - 170°W, also called the "Niña 3.4 region"). El Niño conditions exist when the SST in this region rises 0.5°C above average. As of July 9, 2012, SSTs in the Niño 3.4 region had risen to 0.5°C above average. To be considered an "El Niño episode", El Niño conditions must occur for five consecutive months, using 3-month averages. Image credit: NOAA Climate Prediction Center.

Wind shear: above average
Wind shear is usually defined as the difference in wind between 200 mb (roughly 40,000 foot altitude) and 850 mb (roughly 5,000 foot altitude). In most circumstances, wind shear above 20 knots will act to inhibit tropical storm formation. Wind shear below 12 knots is very conducive for tropical storm formation. High wind shear acts to tear a storm apart. The jet stream has two bands of strong high-altitude winds that are currently bringing high wind shear to the Atlantic. The southern branch (subtropical jet stream) is bringing high wind shear to the Caribbean, and the northern branch (polar jet stream) is bringing high wind shear to the waters offshore of New England. This configuration often leaves a "hole" of low shear between the two branches, off the Southeast U.S. coast and over the Gulf of Mexico. The jet stream is forecast to maintain this two-branch pattern over the coming two weeks. Wind shear has been about 10 - 20% higher than average over the first two weeks of July, and is predicted to be mostly above average for the coming two weeks. This will cut down on the odds of a July storm.


Figure 5. Vertical instability over the Caribbean Sea in 2012 (blue line) compared to average (black line.) The instability is plotted in °C, as a difference in temperature from near the surface to the upper atmosphere. Thunderstorms grow much more readily when vertical instability is high. Instability has been lower than average, due to an unusual amount of dry air in the atmosphere, reducing the potential for tropical storm formation. Image credit: NOAA/NESDIS/CIRA.

Dry air: above average
As seen in Figure 5, there has been an unusual amount of dry, stable air in the Caribbean this year creating low levels of vertical instability. This has occurred due to a combination of dry air from Africa, and upper-atmosphere dynamics creating large areas of sinking air that dry as they warm and approach the surface. The Gulf of Mexico and tropical Atlantic between the coast of Africa and the Lesser Antilles have also seen low vertical instability this summer. June and July are the peak months for dry air and dust coming off the coast of Africa, and the Saharan dust storms have been quite active over the past two weeks. Expect dry air to be a major deterrent to any storms that try to form in the tropical Atlantic during July.

Steering currents: average
The predicted steering current pattern for the next two weeks is a typical one for July. We have an active jet stream bringing many troughs of low pressure off the East Coast of the U.S. These troughs are frequent enough and strong enough to recurve any tropical storms or hurricanes that might penetrate north of the Caribbean Sea. Steering current patterns are predictable only about 3 - 5 days in the future, although we can make very general forecasts about the pattern as much as two weeks in advance. There is no telling what might happen during the peak months of August, September, and October--we might be in for a repeat of the favorable 2010 and 2011 steering current pattern, which recurved most storms out to sea--or the unfavorable 2008 pattern, which steered Ike and Gustav into the Gulf of Mexico.

Summary: a below average chance of a July tropical storm
Given that none of the computer models are forecasting tropical storm formation in the coming seven days, SSTs are only slightly above average, and wind shear and vertical stability are above average, I'll go with a 30% chance of a named storm forming in the Atlantic during the remainder of July.


Figure 6. Hurricane Emilia over the Eastern Pacific at 20:35 UTC July 10, 2012. At the time, Emilia was a Category 3 hurricane with 125 mph winds. Emilia peaked earlier in the day as a Category 4 storm with 140 mph winds--the strongest hurricane in the East Pacific so far in 2012. Image credit: NASA.

An active Eastern Pacific hurricane season
It's been a very active start to the Eastern Pacific hurricane season, where we've already had six named storms, four hurricanes, and three intense hurricanes. A typical season has 4 named storms, 2 hurricanes, and 0 intense hurricanes by July 14. The formation of Tropical Storm Fabio on July 12 marks the 4th earliest formation of the Eastern Pacific's season's sixth storm. The record is held by the year 1985, when the season's sixth storm formed on July 2. Record keeping began in 1949.

Have a great weekend, everyone, and I'll be back Monday with a new post.

Jeff Masters

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Quoting barbamz:
Germany: "Nado"-Land? After posting a video showing a tornado at the coast of the Northern Sea some days ago, there is another short but very close one from today showing another tornado in Remscheid (northwestern part of Germany):

youtube

There is another quite impressive video from a more distant perspective on youtube but I don't want to post it because of the kind of redneck commentary, lol.


You can WU me the other one. I would like to see it.
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got me a nice line of tstorms comin, and doing its best to miss me:

front edge is actually rollin' along like a cylinder:

Member Since: February 11, 2012 Posts: 0 Comments: 9727
Quoting sunlinepr:

Remnants of Hurricane Daniel south of Hawaii.

Member Since: July 21, 2011 Posts: 83 Comments: 7167
The count will be 3 hurricanes

3 ghosts...

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Only half a globe tonight. Look at that massive convection over Central Africa.

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and to be honest it is not really going to make one difference which side you be on in the end

cause what ever is to be we face it together
and there is nothing no one can do to stop it

faster faster we go
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Quoting yoboi:


guess ya didn't get the TWC memo concerning that...


give up on the TWC stuff already
Member Since: February 11, 2012 Posts: 0 Comments: 9727
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Quoting CosmicEvents:
I'm not pointing fingers at anyone in particular, but of course.
On both sides of the debate.
The multi-national corporations do have more money to throw around, an unlimited amount really. As opposed to the scientists who have little. But there's special interests with money on both sides.


well i do it for free

and in no way take any monies for my views on the subject of global killing
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Quoting aspectre:
506 Grothar: I nailed this days ago.

Well, kinda. You did predict the northward turn far earlier than anyone else.
You also predicted that it would be a threat to the mainMexican or the BajaCalifornian coastline.
The prediction models don't include the coastline... as yet.
See, we do pay attention to more than just your jokes.

Let cruise ships at sea beware...
. . . . . Hurricane...

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . and Bodice Ripper


Fun fact: Fabio was one of my aunt's celebrity crushes.
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Hurricane Fabio:

Member Since: July 21, 2011 Posts: 83 Comments: 7167
Germany: "Nado"-Land? After posting a video showing a tornado at the coast of the Northern Sea some days ago, there is another short but very close one from today showing another tornado in Remscheid (northwestern part of Germany):

youtube

There is another quite impressive video from a more distant perspective on youtube but I don't want to post it because of the kind of redneck commentary, lol.
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Quoting Grothar:
Sorry I haven't posted more. I was stuck on post 465 for about an hour and found myself repeating, "Danger, Will Robinson" over and over.

Been getting stuck a lot too. And antagonistically one post above or below a graphic I REALLY want to look at :(
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Quoting ncstorm:
People get paid to blog on this site?
I'm not pointing fingers at anyone in particular, but of course.
On both sides of the debate.
The multi-national corporations do have more money to throw around, an unlimited amount really. As opposed to the scientists who have little. But there's special interests with money on both sides.
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544. yoboi
Quoting ncstorm:
People get paid to blog on this site?


guess ya didn't get the TWC memo concerning that...
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Quoting ncstorm:
18z Nogaps misses Central America with the tropical wave/Low and starts bringing it NW instead of straight into CA





Looks like we may have some model agreement on future Ernesto.
Member Since: August 14, 2010 Posts: 10 Comments: 16971
Sorry I haven't posted more. I was stuck on post 465 for about an hour and found myself repeating, "Danger, Will Robinson" over and over.
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Quoting AtHomeInTX:


The ice storm I remember. What piece of useless information replaced the 2002 flooding in my memory I'll never know. lol. Ah anyway


Don't feel bad, I'd forgotten it as well and don't know how I did.
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Somebody get this man a fresca, he's earned it.

Quoting Grothar:
I nailed this days ago.


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Quoting yoboi:


yep and it will get strong like louisiana ice storm strong


The ice storm I remember. What piece of useless information replaced the 2002 flooding in my memory I'll never know. lol. Ah anyway...

October/November 2002 Heavy Rainfall and Flooding
October 20 - November 5, 2002
by Montra Lockwood, Service Hydrologist


During the last 10 days of October, an upper level trough stalled over the region with numerous disturbances moving across the area. This provided several days of widespread rainfall. The precipitation was further enhanced by a stationary front located across southeast Texas into southwest and central Louisiana, as well as by the remnants of Hurricane Kenna moving northeast across the area from old Mexico. As a result, very heavy rainfall occurred in many areas.

On the 29th, water up to 8 feet deep was reported on underpasses in Beaumont, TX, and one person
died after driving a car into a flooded underpass. In Vinton, LA, the fire department reported nearly
half the streets in the town were extensively flooded, while the Iberia parish sheriff reported numerous
streets throughout the parish under water.
Moderate to major flooding occurred on several rivers. Water began reaching homes near Old Town
Bay and Sam Houston Jones State Park on the lower Calcasieu River, as well as along the Pine
Island Bayou near Sour Lake, TX. At several sites, river levels were still rising at the end of the
month.
For the month of October, rainfall records were broken at Lake Charles and Lafayette, with 21.44 and
18.27 inches, respectively. This was the fourth wettest October for Beaumont, with a monthly total of
14.05 inches. The totals for Alexandria and New Iberia were also well above normal, with 12.49
inches of rain reported at Alexandria International Airport and 12.63 inches reported at Acadiana
Regional Airport in New Iberia.
The flood waters had little time to recede before another strong storm system brought more heavy
rains to the area from November 2nd through the 5th. In a pattern similar to the October storm, an
upper trough became stationary over the region, as an active subtropical jet pulled moisture across
the Gulf Coast states. Several disturbances moved through the flow, allowing several rounds of
moderate to heavy rain to fall across southeast Texas and southern Louisiana...
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People get paid to blog on this site?
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Member Since: July 21, 2011 Posts: 83 Comments: 7167
Quoting aspectre:
Grothar, you might wanna look at my response in 507 to your comment506...
...the quibble could be a mismemory on my part.


Gee, aspectre, you're going to make me blush. :)
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Gotta go back out again:(
Member Since: March 16, 2012 Posts: 127 Comments: 7942
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN DIEGO CA
200 PM PDT FRI JUL 13 2012

.SYNOPSIS...
UPPER LEVEL LOW WILL REMAIN OVER THE REGION THROUGH TONIGHT...WITH
SCATTERED TO NUMEROUS SHOWERS AND THUNDERSTORMS. FLASH FLOODING IS
POSSIBLE WITH SOME OF THE STRONGER STORMS. AS THIS LOW SLOWLY
SHIFTS EAST...SHOWERS AND THUNDERSTORMS WILL LINGER OVER THE REGION
THROUGH SATURDAY...BUT MAINLY OVER THE MOUNTAINS AND DESERTS. A
TROUGH OF LOW PRESSURE WILL THEN DIG ALONG THE WEST COAST FOR THE
LATTER PART OF THE WEEKEND AND EARLY NEXT WEEK...WITH COOLER AND
DRIER CONDITIONS RETURNING.

FOR THURSDAY THROUGH NEXT FRIDAY...INCREASE CLOUDS AND RAISED
DEWPOINTS AND HUMIDITY TO REFLECT OUTFLOW/REMNANTS OF TROPICAL
CYCLONE FABIO BEING CAUGHT UP IN THE BOTTOM END OF THE TROUGH AND
ADVECTED UP AND OVER SSW CALIFORNIA/NRN BAJA CALIFORNIA. WILL HAVE
TO WATCH THIS AND REFINE MORE CLOSELY NEXT WEEK.
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533. yoboi
Quoting CosmicEvents:
Demeaning members one at a time. PensacolaDoug, I think we finally a point of agreement.
.
In any case, there's better posters, paid or not, by either side, that get "the message" across without the abrasive sidebars.



i wish both sides would pay me i can serve kool-aid in 2 lines.....
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Member Since: March 16, 2012 Posts: 127 Comments: 7942
Quoting PensacolaDoug:




Charming as ever Nea!
Demeaning members one at a time. PensacolaDoug, I think we finally found a point of agreement.
.
In any case, there's better posters, paid or not, by either side, that get "the message" across without the abrasive sidebars.
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Member Since: July 21, 2011 Posts: 83 Comments: 7167
529. yoboi
Quoting Grothar:
I nailed this days ago.




nail it gro nail it nail it like there is no tomm...
gro you are a great teacher keep up the great work...
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Quoting Neapolitan:
Oh, I believe you. What would some silly professional, educated, Canada-based natural hazards researcher know about Alaskan or Canadian natural hazards, anyway? ;-)
Well, thanks, Neo. I'm guessing it wasn't me that convinced you. Probably the map BobWallace posted at comment 498. Have a nice eve.
:)
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Grothar, you might wanna look at my response in 507 to your comment in 506...
...the quibble could be a mismemory on my part.
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526. yoboi
Quoting OrchidGrower:


Would really like to see that NWS article, Largo! I'd love to live purely tropical, but the bits of "climate-change forecast" I've been hearing for Florida is drier and drier weather in the decades to come (--No Thanks!!!!!).

...Not to mention it'd be a whole lot less traumatic if I just moved farther south, rather than the global tropical airmass expand poleward!! ;-)


ya thinkin cuba???
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Lots of flooding and flash flooding in the SWLink
Member Since: March 16, 2012 Posts: 127 Comments: 7942
Quoting LargoFl:
just a note to everyone..i wish i could find the chart again..i posted it a couple of days ago..BUT..there IS a sort of climate change coming soon...our florida and gulf coast semi-tropical climate is steadily moving northward..NC and iowa etc will soon be seeing as normal..OUR summer weather , i guess even the humidty and temps..that was from the NWS page...........so a climate shift IS going to happen..i just hope..this is not the beginning of something, and I am wondering if..this shift does occur as they say it will...what will MY climate be like here in florida?..not semi tropical anymore but pure tropical in nature?..oh boy, and if this change does happen...what I really want to know is..how will that change affect Their winters?..remember melting snows in spring..feed the rivers like the mississippi etc


Would really like to see that NWS article, Largo! I'd love to live purely tropical, but the bits of "climate-change forecast" I've been hearing for Florida is drier and drier weather in the decades to come (--No Thanks!!!!!).

...Not to mention it'd be a whole lot less traumatic if I just moved farther south, rather than the global tropical airmass expand poleward!! ;-)
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523. THL3
Quoting TropicalAnalystwx13:

Slow internet connection and....do you have LargoFL on ignore?


Probably my internet, I'm on sat with lots of weather in the area. Over 10" of rain for July so far, its great.
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18z Nogaps misses Central America with the tropical wave/Low and starts bringing it NW instead of straight into CA





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Just for entertainment, let's look at the Maya stuff that's floating around the blog.

The calendar (which also kept track of lunar/solar/planetary patterns) simply runs out on December 21, 2012, right? Tell me, please, would you keep track of lunar/solar/planetary patterns as far into the future as 2500 AD? Didn't think so...and if you wouldn't, why would they? Anyways, the Mayans decided that in 500 years, they could scrawl more dates into the wall of their cave and they left it at that. Now, this is further evidenced by some ancient planning freak who decided it would be a fantastic idea to make his calendar stretch even further into the future than the one that was discovered back in 1915. This calendar that was recently discovered this year (Link) goes 1500 years further than the one everyone has been terrified of for so long.

Plus this post if you plan on being alive and kicking on Saturday, December 22, 2012.

Fabio looks better (there, now I'm on topic).

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Quoting TropicalAnalystwx13:
This year too?

2011 PHS:



2012 PHS:



A majority of the storms are becoming hurricanes...and eventually major hurricanes.

This is crazy.
Member Since: July 21, 2011 Posts: 83 Comments: 7167
This year too?

2011 PHS:



2012 PHS:



A majority of the storms are becoming hurricanes...and eventually major hurricanes.
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518. yoboi
Quoting AtHomeInTX:
Ok, first af all, never thought I'd read these words together in a sentence. lol And secondly, it looks like El Nino is making his presence known.

NATIONAL WEATHER SERVICE LAKE CHARLES LA
324 PM CDT FRI JUL 13 2012

THE GOOD NEWS IS THAT RIDGING CONTINUES TO BUILD IN FROM THE EAST
NEXT WEEK.
SINCE THE ATMOSPHERE WILL STILL BE MORE MOIST THAN
NORMAL, THE COMPROMISE SOLUTION LOOKS TO BE FOR CLIMO 30 PERCENT DAYTIME
POPS NEXT WEEK. SOME LOCAL RESEARCH INTO THE LENGTH OF THIS
ONGOING PRECIP EVENT HERE REVEALS THAT OCT OF 2002 SAW A SIMILAR
SETUP WITH AN INCIPIENT EL NINO ACTING UPON A WEAKNESS IN THE
UPPER LEVEL RIDGE WHICH DEVELOPED INTO A QUASISTATIONARY LOW OR
UPPER TROF AND A TWO WEEK EVENT SIMILAR TO THE CURRENT ONE. THANKS
TO OUR MR RUA FOR THIS INFO.


yep and it will get strong like louisiana ice storm strong
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Quoting THL3:


The blog is kinda stuck on 507 and skips to 511 and 512. Unless everyone left for the evening.....

Slow internet connection and....do you have LargoFL on ignore?
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516. THL3
Quoting TropicalAnalystwx13:

Depends. What's wrong with it?


The blog is kinda stuck on 507 and skips to 511 and 512. Unless everyone left for the evening.....
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For those who are interested, I've made a blog update on Fabio and Emilia.
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Quoting Grothar:
I nailed this days ago.



You did indeed, I remember, lol. Congrats.
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Member Since: July 21, 2011 Posts: 83 Comments: 7167
Quoting THL3:
What happened to the blog?

Depends. What's wrong with it?
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511. THL3
What happened to the blog?
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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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