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 Levi32:


This is not cooling. This is noise.



was wondering about that.
but with all the articles abounding and blog despair i thought maybe it wasnt noise after all.
It still might not be, never know if its noise or a setback.
He's coming anyway, no way to stop El Nino now
Member Since: February 11, 2012 Posts: 0 Comments: 9721
1960. Levi32
Quoting floridaboy14:
levi what analouge year does 2012 resemble?


We followed 2006 pretty closely in the month of June.
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1959. Houdude
That blob in the Central Atlantic at 30 W, 10 N sure looks like its got a low level spin.
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Quoting Levi32:


This is not cooling. This is noise.



All credit to Stormchaser2007.
Member Since: July 6, 2010 Posts: 113 Comments: 31541
Quoting Grothar:



LOL. I don't think to many remember that!


Only the old farts....lol
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Quoting Gearsts:
Do you think this season we here in PR will be at less risk for any tropical storm? :)


If the high pressure to our north is relativly strong it will cause the tracks of any system that forms east of the islands to track South of PR.But if that high weakens then is another story.
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Gonna break off for today and do some things with the kids. Just noting that everyone is still here today in spite of the solar flare issues......... Have a Great Day Folks and see Yall Tomorrow.
Member Since: August 8, 2006 Posts: 0 Comments: 8831
1954. Levi32
Quoting Gearsts:
What do you think is causing the cooling in the El nino region and the positive SOI delaying the El nino?


This is not cooling. This is noise.

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1953. Levi32
So how about if I use the current motion of the plane to extrapolate its position forward from the latest data point such that it is out of the way of the data. The actual position of the plane 30 seconds later usually doesn't deviate much from the previous flight path anyway, so it would be reasonably accurate. Like this:

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1952. Gearsts
Quoting Tropicsweatherpr:


Thank you for the brief explanation. I lean towards the first 10 days of August for TC formation.
Do you think this season we here in PR will be at less risk for any tropical storm? :)
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Was watching a show on NatGeo last night (one of those weather "disaster" shows) and one of the Mets who was commenting on the 1992 big cane that hit Hawaii (that vid clip with the roof peeling off of a house) mentioned that fact of how topical storms love that hot water over 80 and that the El Nino warming effect that year, on the E-Pac side, contributed to the strength of that storm. Not surprising then that the E-Pac is so active this El Nino year (even under relatively mild conditions).

Ironic that Andrew developed into the monster that it did on the Atlantic side that year also even with El Nino conditions.
Member Since: August 8, 2006 Posts: 0 Comments: 8831
1950. Gearsts
Quoting Levi32:


Probably not this month. The only sparkle of potential action is the CFSv2 and JMA ensembles showing a burst of southeasterly winds moving into the southeast Caribbean during Weeks 3 and 4, something that could generate some activity if it comes to fruition, but the month-long forecasts often change a lot.

What do you think is causing the cooling in the El nino region and the positive SOI delaying the El nino?
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Polish Tornado Outbreak
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Quoting Levi32:


Probably not this month. The only sparkle of potential action is the CFSv2 and JMA ensembles showing a burst of southeasterly winds moving into the southeast Caribbean during Weeks 3 and 4, something that could generate some activity if it comes to fruition, but the month-long forecasts often change a lot.

levi what analouge year does 2012 resemble?
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Quoting Levi32:


Probably not this month. The only sparkle of potential action is the CFSv2 and JMA ensembles showing a burst of southeasterly winds moving into the southeast Caribbean during Weeks 3 and 4, something that could generate some activity if it comes to fruition, but the month-long forecasts often change a lot.



Thank you for the brief explanation. I lean towards the first 10 days of August for TC formation.
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Quoting Levi32:


Probably not this month. The only sparkle of potential action is the CFSv2 and JMA ensembles showing a burst of southeasterly winds moving into the southeast Caribbean during Weeks 3 and 4, something that could generate some activity if it comes to fruition, but the month-long forecasts often change a lot.

levi what analouge year does 2012 resemble as of now?
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Given the current low shear and high SST environment of the Gulf of Mexico its not surprising to see at least a few ensemble members try to get something going. In this case it is 4/20 CMC members that set something off in the short-term. Not likely given the lack of vorticity in the area, but you can't blame an ensemble member for trying :)
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1943. beell
No plane. Data only, please.
Felix the cat would be nice if you have to put something there.
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1942. Levi32
Quoting Tropicsweatherpr:
Levi,anything on the horizon for something to develop in the North Atlantic in the next three weeks?


Probably not this month. The only sparkle of potential action is the CFSv2 and JMA ensembles showing a burst of southeasterly winds moving into the southeast Caribbean during Weeks 3 and 4, something that could generate some activity if it comes to fruition, but the month-long forecasts often change a lot.

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1941. Grothar
Quoting weathermanwannabe:


That is a really nice analog comparison and explanation...........Thanks for that.

Another point to consider with SAL issues is the slight cooling effect a heavy layer can have on SST's just to the North of the ITCZ. When SAL clears out, the water temps can move up a notch.


Good point.
Member Since: July 17, 2009 Posts: 69 Comments: 25434
1940. Grothar
Quoting HurricaneHunterJoe:
B= De Plane De Plane......Boss.....it'sDePlane...I vote for the PLANE.



LOL. I don't think to many remember that!
Member Since: July 17, 2009 Posts: 69 Comments: 25434
Quoting Levi32:


No the latest data point is plotted normally, and then the tail of the plain is positioned near that point, fairly similar to the Google Earth feature that we all know and love.


if you are worried about the plane being in the way, make it the last data set and it might help a tad since you are most likely to look at the last recon data
Member Since: February 11, 2012 Posts: 0 Comments: 9721
1938. Grothar
Quoting Patrap:

1904. Grothar

A Lady friend in Boca perhaps?


She's in Miami, and who told???
Member Since: July 17, 2009 Posts: 69 Comments: 25434
Quoting Levi32:


No the latest data point is plotted normally, and then the tail of the plain is positioned near that point, fairly similar to the Google Earth feature that we all know and love.
hey levi when will you make a tropical tidbit? its been a while :)
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1936. Patrap
Member Since: July 3, 2005 Posts: 421 Comments: 127647
A couple minutes ago when I posted the 2 images of the GFS it took a couple minutes to appear on this site.
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Quoting TropicalAnalystwx13:

We said feedback issues for Debby too and look what happened.

I'm not discounting anything the GFS shows this season. It has performed very well this season, nailing the formation of Alberto, Beryl, Chris, and Debby, as well as the tracks.


i know what happened, there was no ernesto like we said
Member Since: February 11, 2012 Posts: 0 Comments: 9721
For those having problems with the sight. I rebooted and the problems have stopped. I was having big time problems just loading and refreshing before I did.
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Levi,anything on the horizon for something to develop in the North Atlantic in the next three weeks?
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Quoting TropicalAnalystwx13:

It'd be amazing if we got Ernesto, Florence, and Gordon off the East Coast as the GFS has been so adamantly been showing.

12Z:



06Z:



00Z:



Im not gonna go against the GFS after the job it did with Debby.........but 3 storms, like it projects?.....Ummmmmmmmm.....I don't know!
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1930. Levi32
Quoting GeorgiaStormz:


not recently has the gfs been accurate on time.
and 3TCs = something wrong on the GFS maybe feedback

i like the plane, does the plane = the last data set?


No the latest data point is plotted normally, and then the tail of the plain is positioned near that point, fairly similar to the Google Earth feature that we all know and love.
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1914. Levi32

I would go with the plane too, it looks cool on that graphics.
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Quoting GeorgiaStormz:


not recently has the gfs been accurate on time.
and 3TCs = something wrong on the GFS maybe feedback

i like the plane, does the plane = the last data set?

We said feedback issues for Debby too and look what happened.

I'm not discounting anything the GFS shows this season. It has performed very well this season, nailing the formation of Alberto, Beryl, Chris, and Debby, as well as the tracks.
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1927. Levi32
I can also make the data appear in the foreground above the plane if it helps to see it better, but it's not much more obstructive than the Google Earth recon plane icon.

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B= De Plane De Plane......Boss.....it'sDePlane...I vote for the PLANE.
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A 15 second time lapse picture my friend took and posted on Facebook last night:

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Quoting Levi32:
Good afternoon all. If I could get a quick opinion poll from you guys:

For live plotted recon data, would you rather that the latest observation in the set be highlighted and "bolded" (top image), or would you rather have an image of an airplane located at the latest data point and rotated in the aircraft's direction of travel (bottom image). I need to decide which to use. Personally I like the plane, but I'm curious which you guys prefer. Sometimes the plane can get in the way of the data.

Highlighted:



Aircraft Icon:



I prefer the airplane.
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Quoting Grothar:
Sometimes there is a confusion about the SAL or Saharan Air Layer. It is actually composed of actually 3 layers. A top layer,which is hot and dry; the mid layer, which is cooler air from the Atlantic; and a third layer which is cooler dense air from the Atlantic.

Sometimes dust storms mix with this layer. Actually, Most scientists agree that the SAL actually aid in the formation of some hurricanes by using these components to cause a spin. Heavy amounts of dust are not always in the SAL.

The SAL can inhibit the development of hurricanes,because of the level of moisture in the mid-level. If it is too dry, development becomes less likely.


Here is an example of Hurricane Erin forming within a strong SAL environment.


That is a really nice analog comparison and explanation...........Thanks for that.

Another point to consider with SAL issues is the slight cooling effect a heavy layer can have on SST's just to the North of the ITCZ. When SAL clears out, the water temps can move up a notch.
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1922. Dakster
Quoting Grothar:
Exactly as I predicted in my blog 5 days ago. How do I know these things??



I give up...

HOW?
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Quoting TropicalAnalystwx13:

"too weak"= High pressure environment
"subtropical"= could easily transition or start tropical to begin with
"took us a month to get 1"= I honestly don't understand why you keep saying this. When the GFS shows a tropical cyclone and it verifies, it's usually within 2 days time of the day it showed the TC forming on to begin with.

No NODATA message here.


not recently has the gfs been accurate on time.
and 3TCs = something wrong on the GFS maybe feedback
Quoting Levi32:
Good afternoon all. If I could get a quick opinion poll from you guys:

For live plotted recon data, would you rather that the latest observation in the set be highlighted and "bolded" (top image), or would you rather have an image of an airplane located at the latest data point and rotated in the aircraft's direction of travel (bottom image). I need to decide which to use. Personally I like the plane, but I'm curious which you guys prefer. Sometimes the plane can get in the way of the data.

Highlighted:



Aircraft Icon:




i like the plane, does the plane = the last data set?
Member Since: February 11, 2012 Posts: 0 Comments: 9721
Quoting Levi32:
Good afternoon all. If I could get a quick opinion poll from you guys:

For live plotted recon data, would you rather that the latest observation in the set be highlighted and "bolded" (top image), or would you rather have an image of an airplane located at the latest data point and rotated in the aircraft's direction of travel (bottom image). I need to decide which to use. Personally I like the plane, but I'm curious which you guys prefer. Sometimes the plane can get in the way of the data.

Highlighted:



Aircraft Icon:




I also like the plane.
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Quoting Levi32:
Good afternoon all. If I could get a quick opinion poll from you guys:

For live plotted recon data, would you rather that the latest observation in the set be highlighted and "bolded" (top image), or would you rather have an image of an airplane located at the latest data point and rotated in the aircraft's direction of travel (bottom image). I need to decide which to use. Personally I like the plane, but I'm curious which you guys prefer. Sometimes the plane can get in the way of the data.

Highlighted:



Aircraft Icon:




I vote B
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1918. Patrap
#1914

"latest observation in the set"

Dat's my view and opine.

Sometimes the plane can get in the way of the data.

..and I concur, the plane is WAY too large a icon.
Member Since: July 3, 2005 Posts: 421 Comments: 127647
I am not encountering any problems on the blog for the person who asked earlier.
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Quoting Levi32:
Good afternoon all. If I could get a quick opinion poll from you guys:

For live plotted recon data, would you rather that the latest observation in the set be highlighted and "bolded" (top image), or would you rather have an image of an airplane located at the latest data point and rotated in the aircraft's direction of travel (bottom image). I need to decide which to use. Personally I like the plane, but I'm curious which you guys prefer. Sometimes the plane can get in the way of the data.

Highlighted:



Aircraft Icon:



I like the plane as well.
Member Since: July 6, 2010 Posts: 113 Comments: 31541
Quoting GTcooliebai:
Along trough splits yeah, but if the trough makes it down all the way into the gulf and sits stationary for days you can get development in the gulf, like Hurricane Gabrielle in 2001. We'll have to keep looking for trends to see if the GFS pushes the trough further south and something develops on the tail of it.


Thanks
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1914. Levi32
Good afternoon all. If I could get a quick opinion poll from you guys:

For live plotted recon data, would you rather that the latest observation in the set be highlighted and "bolded" (top image), or would you rather have an image of an airplane located at the latest data point and rotated in the aircraft's direction of travel (bottom image). I need to decide which to use. Personally I like the plane, but I'm curious which you guys prefer. Sometimes the plane can get in the way of the data.

Highlighted:



Aircraft Icon:


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Quoting Grothar:
Exactly as I predicted in my blog 5 days ago. How do I know these things??



Because you are the Guru! This is what Guru's do!!
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Quoting GeorgiaStormz:


too weak and subtropical and fedback.
Last time the GFS had 3 storms, took us a month to get 1.

BTW, does anyone keep getting a NODATA message when they try to get on the blog?

"too weak"= High pressure environment
"subtropical"= could easily transition or start tropical to begin with
"took us a month to get 1"= I honestly don't understand why you keep saying this. When the GFS shows a tropical cyclone and it verifies, it's usually within 2 days time of the day it showed the TC forming on to begin with.

No NODATA message here.
Member Since: July 6, 2010 Posts: 113 Comments: 31541
Quoting Ameister12:
Anybody else having problems with Dr. Masters blog?


a NODATA thing?
thats what i have
Member Since: February 11, 2012 Posts: 0 Comments: 9721

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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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