Major severe thunderstorm outbreak expected; U.S. drought intensifies

By: Dr. Jeff Masters , 2:16 PM GMT on July 26, 2012

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A dangerous outbreak of organized severe thunderstorms with strong, damaging winds is expected this afternoon from Ohio eastwards through Pennsylvania and into New England, says NOAA's Storm Prediction Center (SPC). They have put the region, which includes Columbus, Pittsburgh, Philadelphia, and New York City, in their "Moderate Risk" area for severe weather, just one notch below the highest level of alert. Much of the region is also under advisories for extreme heat, with temperatures in the upper 90s expected. This extreme heat will help energize the thunderstorms by making the atmosphere very unstable. A cold front passing through the region will trigger the severe weather episode beginning around 2 pm EDT this afternoon, near the Indiana/Ohio border. This front already triggered a round of severe thunderstorms early this morning across Michigan, which knocked out power to 16,000 customers. This afternoon, severe thunderstorms may organize into a complex that features a bow-shaped echo. If such a complex brings violent straight-line winds in excess of 58 mph (93 km/hr) over a swath of at least 240 miles (about 400 km), it will be called a derecho (from the Spanish phrase for "straight ahead".) The atmosphere is not as unstable as was the case for the June 29 - 30 Mid-Atlantic and Midwest derecho, however. That storm was one of the most destructive and deadly fast-moving severe thunderstorm complexes in North American history. It killed 22 people, knocked out power to at least 3.7 million customers, and did hundreds of millions in damage.


Figure 1. Severe weather risk for Thursday, July 26, 2012, from NOAA's Storm Prediction Center (SPC).

U.S. drought intensifies
The great U.S. drought of 2012 held constant in size but grew more intense over the past week, said NOAA in their weekly U.S. Drought Monitor report issued Thursday, July 26. The area of the contiguous U.S. covered by drought stayed constant at 64% , but the area covered by severe or greater drought jumped from 42% to 46%. These are truly historic levels of drought, exceeded only during the great Dust Bowl drought of the 1930s and a severe drought in the mid-1950s. The July 2012 drought is second only to the great Dust Bowl drought of July 1934 in terms of the area of the contiguous U.S. covered by moderate or greater drought (if we assume the drought conditions measured in mid-July are representative of the entire month of July, which is a reasonable approximation given the lastest drought forecast.) The five months with the greatest percent area in moderate or greater drought, since 1895, now look like this:

1) Jul 1934, 80%
2) Jul 2012, 64%
3) Dec 1939, 60%
4) Jul 1954, 60%
5) Dec 1956, 58%

If we consider the area of the contiguous U.S. covered by severe or greater drought, drought conditions as of July 24, 2012 now rank in 3rd place:

1) Jul 1934, 63%
2) Sep 1954, 50%
3) Jul 2012, 46%
4) Dec 1956, 43%
5) Aug 1936, 43%


Figure 2. July 24, 2012 drought conditions showed historic levels of drought across the U.S., with 64% of the contiguous U.S. experiencing moderate or greater drought, and 46% of the county experiencing severe or greater drought. Image credit: U.S. Drought Monitor.

Extreme heat continues in the Heartland
St. Louis, Missouri's summer of extreme heat reached record levels on Wednesday, when the city hit 108°F. This marked the 11th day this summer in St. Louis with temperatures of at least 105°F, beating the old record of ten such days in 1934. The minimum temperature in the city fell to just 86°F, tying with July 24, 1901, as the warmest minimum temperature ever recorded in the city. St. Louis has seen just 0.53" inches of rain this month, far below the normal 3.35" it usually records by this point in July.

Jeff Masters

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1499. LargoFl
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1498. LargoFl
Quoting OrchidGrower:
What do we think the trough is going to bring for Florida? I watched TWC this morning, was appalled to see a week's worth of near-cloudless suns on their graphic for our 7-day forecast -- i.e., no rain in what is supposed to be the heart of our rainy season here in SW FL. (Of course, they could end up being wrong, but just the thought of a week at hot, dry and rainless is appalling!)
..slight showers are developing here near Pinellas,we may get the usual summertime sea breeze showers in the afternoon, nothing organized
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Each state in the US currently has some portion of it in at least the abnormally dry category:

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1496. LargoFl
Quoting reedzone:
Similar pattern setups from Frances (2004), Isabel (2003), Floyd (1999), Irene (2011), and Earl (2010)... either the trough is strong enough to bring a storm up the East Coast or the trough is weaker and allows the storm to move WNW to NW and hit the Southeast.
..Georgia sure could use its rains
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Quoting osuwxguynew:
The three climate model outputs that I've looked at, (JMA, Eurosip, and CFSv2) suggest enhanced subsidence and associated reduced TC development across the central and eastern Atlantic on average throught the remainder of the season.

Given the cooler SSTs/lower oceanic heat content and the likely continuation of the dry/stable pattern ongoing since last winter, I'm thinking the models will probably pan out. Most development will be in the western half of the basin, and will be reduced for the season overall.



Yup!
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Similar pattern setups from Frances (2004), Isabel (2003), Floyd (1999), Irene (2011), and Earl (2010)... either the trough is strong enough to bring a storm up the East Coast or the trough is weaker and allows the storm to move WNW to NW and hit the Southeast.
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Quoting islander101010:
hopefully.by.then.el.nino


Well have El-nino of +7C or +8C come next Monday on CPC's update as there has been a huge increase in sea surface anomalies over the last few days across Nino 1&2 and Nino 3.4.
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Quoting reedzone:


Wrong, this is the type of pattern similar to Frances in 2004. Strong ridge in the Atlantic, weak trough off the East Coast, not strong enough for a recurvature out to sea. This would bring a storm into the Southeast.


I never said the US is safe as that pattern being detected by the GFS is worrisome as it is showing a weak trough across the SE US and extending into FL. Just have to wait and see.
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1490. Grothar
Quoting weathermanwannabe:


The models are going to start picking up on "lots" of waves coming off Africa over the next 4 weeks and we will start seeing consensus runs for development; this is just the beginning.............If you consider the average number (cited in a recent NCEP discussion) of waves at around one viable one every 5.5 days emerging off the coast, the next 10 waves (from now through early September) will be contenders for the first long-track Cape Verde storm. We need to watch them all at this point but not all will become tropical depressions or storms.


I seem to remember reading something about that in 1954 when I first started tracking hurricanes. We used to have short wave radios and ham radios back then and we used to have a good time talking to each other. It was the pre-blog days. We would talk to people all over the world and we never met each other. I was thinking of doing a blog on how we did things back then. There were ships stationed over the Atlantic that would give reports. We would all share the information.

The only difference back then, was there was very little fighting. We would have little green ledger sheets and draw our own maps. We would have our rulers and triangles and we would triangulate different positions. We would sometimes pass the information on to different weather services. So I guess we were the pre-Internet bloggers.

I've been thinking of doing a blog called, 100 Years Ago Today, taken from my own journals.:)

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Quoting OrchidGrower:
What do we think the trough is going to bring for Florida? I watched TWC this morning, was appalled to see a week's worth of near-cloudless suns on their graphic for our 7-day forecast -- i.e., no rain in what is supposed to be the heart of our rainy season here in SW FL. (Of course, they could end up being wrong, but just the thought of a week at hot, dry and rainless is appalling!)
bad.sign.for.a.hurricane.strike
Member Since: Posts: Comments:
The three climate model outputs that I've looked at, (JMA, Eurosip, and CFSv2) suggest enhanced subsidence and associated reduced TC development across the central and eastern Atlantic on average throught the remainder of the season.

Given the cooler SSTs/lower oceanic heat content and the likely continuation of the dry/stable pattern ongoing since last winter, I'm thinking the models will probably pan out. Most development will be in the western half of the basin, and will be reduced for the season overall.

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Quoting Skyepony:
Here's a MJO forecast..has things getting active mid Aug.
hopefully.by.then.el.nino
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1486. ncstorm
from Allan Huffman about the trough

The pattern will change next week, with a weakness developing between the heat ridge over the south-central US and the Bermuda High in the western Atlantic. This will lead to a mean trough over the Eastern US and cooler temps, but high humidity, and an increased chance for showers and storms in the afternoon and evening. Temps will likely fall back into the 85-90 range for much of next week for highs.

For late next week into the weekend, the GFS remains near to slightly below normal temperature wise with continued good chances for rain, while the ECMWF warms up a bit (low to mid 90s) with a decreased chance for rain. The ECMWF has been the better model this summer, and thus I wouldn’t be surprised to see temperatures back into the 90-95 range by late next week and for the following weekend.
Member Since: August 19, 2006 Posts: 13 Comments: 17391
1485. Skyepony (Mod)
Here's a MJO forecast..has things getting active mid Aug.
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1484. icmoore
Testing, testing is this Dr M's blog or am I lost? Such a friendly place this morning I hardly recognize it LOL! Shhh I hope I didn't just jinx it :)

Quoting StormTracker2K:


There some cooling showers just north of Largo this morning. Could mean thunderstorms today for the interior.



Yes, I have been seeing a lot of spotty showers coming in from about Palm Harbor to down south of St. Pete this morning.
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Quoting StormTracker2K:



Yeah that trough sets up and just sits there for 7 to 10 days. I wonder if this is a semi permanent pattern setting.

By the way the GFS continues to show lots of moisture gatherning in the NW Caribbean late next week.


Wrong, this is the type of pattern similar to Frances in 2004. Strong ridge in the Atlantic, weak trough off the East Coast, not strong enough for a recurvature out to sea. This would bring a storm into the Southeast.
Member Since: Posts: Comments:
What do we think the trough is going to bring for Florida? I watched TWC this morning, was appalled to see a week's worth of near-cloudless suns on their graphic for our 7-day forecast -- i.e., no rain in what is supposed to be the heart of our rainy season here in SW FL. (Of course, they could end up being wrong, but just the thought of a week at hot, dry and rainless is appalling!)
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Quoting BmtJedi:


I usually depend on Levi to keep us up-to-date on the status of the MJO. He hasn't posted on his blog since the post-Debbie quiet in the Atlantic.



There is a trememdous amount of information about the MJO publicly available here:
CPC MJO Site

The expert discussion from that page is particularly valuable: CPC Expert Discussion


In summary though, the MJO signal is quite weak at the moment with normal, seasonal patterns of convection being the more dominant/evident modes.

The weak signal also makes the future progression of the MJO more uncertain than normal (and normally it's already tough to predict).

It's almost certainly going to continue to be in a phase that causes large scale sinking motion across the Atlantic the next two weeks. I'd say looking at the progression on the 200mb velocity potential chart + the variety of different forecasts, we may have a brief time that is more favorable in the second half of August.
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I have a blog about Ernesto. Visit it and answer the simple question posted there.

Link
Member Since: April 29, 2009 Posts: 75 Comments: 15724
thanks
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Quoting hydrus:
That gathering of moisture is typical when there is a trough near by. Definitely have to watch that, Water temps are very warm.



Moisture pooling up into the East Gulf, FL, and NW Caribbean will be interesting to watch later next week.
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Quoting hydrus:
Well, excuuuuuuse meee...As Steve Martin would say..:)


it's a fetus of a blob.
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1476. hydrus
Quoting StormTracker2K:



Yeah that trough sets up and just sits there for 7 to 10 days. I wonder if this is a semi permanent pattern setting.

By the way the GFS continues to show lots of moisture gatherning in the NW Caribbean late next week.
That gathering of moisture is typical when there is a trough near by. Definitely have to watch that, Water temps are very warm.
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Quoting hydrus:
There is quite a a lot of dust to choke things off a bit, but it is my belief we will have a named storm by August tenth. If some thing forms in the Atlantic, there is a fair chance at recurvature due to a trough and a break in the ridge..Link



Yeah that trough sets up and just sits there for 7 to 10 days. I wonder if this is a semi permanent pattern setting.

By the way the GFS continues to show lots of moisture gatherning in the NW Caribbean late next week.
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1474. Grothar
Quoting hydrus:
Well, excuuuuuuse meee...As Steve Martin would say..:)



LOL. Just a wild and crazy guy!!
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1473. hydrus
Quoting StormTracker2K:


Gro is the Blobologist.
Thats it...BLOB.!BLOB....BLOB!!!
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1472. Grothar
Quoting hydrus:
There is quite a a lot of dust to choke things off a bit, but it is my belief we will have a named storm by August tenth. If some thing forms in the Atlantic, there is a fair chance at recurvature due to a trough and a break in the ridge..Link


I agree.
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1471. BmtJedi
Quoting kshipre1:
does anyone know when the next uptick in the MJO is supposed to be for the atlantic basin? too much dry air out there


I usually depend on Levi to keep us up-to-date on the status of the MJO. He hasn't posted on his blog since the post-Debbie quiet in the Atlantic.
Member Since: Posts: Comments:
Quoting icmoore:
I think it's safe to say it's going to be hot today!

Fair

84°F

Humidity82%
Wind SpeedW 5 mph
Barometer30.08 in (1018.5 mb)
Dewpoint78°F (26°C)
Visibility10.00 mi
Heat Index95°F (35°C)

Last Update on 27 Jul 8:53 am EDT


There some cooling showers just north of Largo this morning. Could mean thunderstorms today for the interior.

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1469. icmoore
I think it's safe to say it's going to be hot today!

Fair

84°F

Humidity82%
Wind SpeedW 5 mph
Barometer30.08 in (1018.5 mb)
Dewpoint78°F (26°C)
Visibility10.00 mi
Heat Index95°F (35°C)

Last Update on 27 Jul 8:53 am EDT
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Quoting hydrus:
Well, excuuuuuuse meee...As Steve Martin would say..:)


Gro is the Blobologist.
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Quoting kshipre1:
does anyone know when the next uptick in the MJO is supposed to be for the atlantic basin? too much dry air out there


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1466. hydrus
Quoting Grothar:


Please, I determine when it is a blob! :) It is currently pre-blobulating.
Well, excuuuuuuse meee...As Steve Martin would say..:)
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Quoting Grothar:
It looks like the 2nd wave coming off of Africa looks pretty good. Maybe this is the one the models keep looking at?




The models are going to start picking up on "lots" of waves coming off Africa over the next 4 weeks and we will start seeing consensus runs for development; this is just the beginning.............If you consider the average number (cited in a recent NCEP discussion) of waves at around one viable one every 5.5 days emerging off the coast, the next 10 waves (from now through early September) will be contenders for the first long-track Cape Verde storm. We need to watch them all at this point but not all will become tropical depressions or storms.
Member Since: Posts: Comments:
does anyone know when the next uptick in the MJO is supposed to be for the atlantic basin? too much dry air out there
Member Since: Posts: Comments:
1463. hydrus
Quoting Grothar:
It looks like the 2nd wave coming off of Africa looks pretty good. Maybe this is the one the models keep looking at?


There is quite a a lot of dust to choke things off a bit, but it is my belief we will have a named storm by August tenth. If some thing forms in the Atlantic, there is a fair chance at recurvature due to a trough and a break in the ridge..Link
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Quoting Neapolitan:
BEGIN
NHC_ATCF
invest_ep912012.invest
FSTDA
R
U
040
010
0000
201207271322
NONE
NOTIFY=ATRP
END
INVEST, EP, E, , , , , 91, 2012, DB, O, 2012072712, 9999999999, , , , , , METWATCH, , EP912012
EP, 91, 2012072700, , BEST, 0, 150N, 1150W, 25, 1009, DB, 0, , 0, 0, 0, 0,
EP, 91, 2012072706, , BEST, 0, 150N, 1150W, 25, 1009, DB, 0, , 0, 0, 0, 0,
EP, 91, 2012072712, , BEST, 0, 150N, 1150W, 50, 996, DB, 34, NEQ, 75, 0, 0, 0, 1008, 150, 0, 0, 0, E, 0, , 0, 0, INVEST, S,
EP, 91, 2012072712, , BEST, 0, 150N, 1150W, 50, 996, DB, 50, NEQ, 50, 0, 0, 0, 1008, 150, 0, 0, 0, E, 0, , 0, 0, INVEST, S,


where's this at?
Member Since: Posts: Comments:
1461. Grothar
Quoting icmoore:
Link

This is a link to a story about some of last night's storm damage.


The little town where our other home is in NE PA got terrible damage. Very large trees down and damage to a lot of homes. Nice article.
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New in the EPAC:

BEGIN
NHC_ATCF
invest_ep912012.invest
FSTDA
R
U
040
010
0000
201207271322
NONE
NOTIFY=ATRP
END
INVEST, EP, E, , , , , 91, 2012, DB, O, 2012072712, 9999999999, , , , , , METWATCH, , EP912012
EP, 91, 2012072700, , BEST, 0, 150N, 1150W, 25, 1009, DB, 0, , 0, 0, 0, 0,
EP, 91, 2012072706, , BEST, 0, 150N, 1150W, 25, 1009, DB, 0, , 0, 0, 0, 0,
EP, 91, 2012072712, , BEST, 0, 150N, 1150W, 50, 996, DB, 34, NEQ, 75, 0, 0, 0, 1008, 150, 0, 0, 0, E, 0, , 0, 0, INVEST, S,
EP, 91, 2012072712, , BEST, 0, 150N, 1150W, 50, 996, DB, 50, NEQ, 50, 0, 0, 0, 1008, 150, 0, 0, 0, E, 0, , 0, 0, INVEST, S,
Member Since: November 8, 2009 Posts: 4 Comments: 14505
1459. Grothar
Quoting hydrus:
yep..Thats healthy lil blob.


Please, I determine when it is a blob! :) It is currently pre-blobulating.
Member Since: Posts: Comments:
1458. Grothar
It looks like the 2nd wave coming off of Africa looks pretty good. Maybe this is the one the models keep looking at?


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1457. hydrus
Quoting Grothar:
The EPAC looks like something wants to start up something


yep..Thats healthy lil blob.
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1456. icmoore
Link

This is a link to a story about some of last night's storm damage.
Member Since: Posts: Comments:
1455. ncstorm
NWS, Wilmington, NC..we shall see..

THIS FRONT ENTERS INTO A REGION
CHARACTERIZED BY 2000-3000 J/KG OF SBCAPE...STRONG MID-LEVEL THETA-E
ADVECTION...AND PWATS IN EXCESS OF 2 INCHES. WHILE THE FRONT WILL
SERVE AS THE PRIMARY FOCUS FOR SURFACE CONVERGENCE...A RATHER ROBUST
VORT MAX WILL ROTATE DOWN JUST SLIGHTLY DELAYED FROM THE FRONT IN
CONJUNCTION WITH THE ADVANCE OF THE RIGHT DIFFLUENT REGION OF A 70KT
300MB JET. MID LEVEL FLOW OF 30-35 KTS HELPS PUSH 0-6KM BULK SHEAR
VALUES TO 20-25 KTS WHILE MID LEVEL LAPSE RATES APPROACH 7 C/KM. SO
WHAT DOES ALL THIS MEAN FOR THE SENSIBLE WEATHER?

EXPECT TO SEE SCATTERED...TO POTENTIALLY WIDESPREAD...CONVECTION
ALONG THE FRONT...WHILE THE BULK SHEAR VALUES SUGGEST MULTI-CELL
COMPLEXES WILL BE THE COMMON MODE. ALTHOUGH THE OVERALL SEVERE WIND
THREAT IS NOT TOO SIGNIFICANT...AND SPC HAS ONLY A SEE TEXT IN THEIR
SWODY2...THE HIGH PWAT AIR WILL SUPPORT ISOLATED WET DOWNBURSTS.
VERY HEAVY RAINFALL IS ALSO LIKELY WITHIN THE STORMS...ESPECIALLY IF
TRAINING CAN OCCUR WITH STORM MOTIONS BEING POTENTIALLY PARALLEL TO
THE BOUNDARY AS IT SAGS SOUTHWARD. ADDITIONALLY...THICK CAPE
PROFILES EVIDENT IN FORECAST SOUNDINGS BETWEEN 0C AND -20C SUGGEST
SOME HAIL IS POSSIBLE (ALTHOUGH CONSIDERABLE MELTING ON THE WAY DOWN
WILL OCCUR MAKING THE OCCURRENCE OF SEVERE HAIL DIFFICULT)...BUT
VIVID LIGHTNING WILL DEFINITELY BE A CONCERN. BELIEVE THE MOS POP
NUMBERS ARE A BIT LOW SO WILL BUMP TO HIGH CHC ACROSS THE
NORTH...LOW CHC ACROSS THE SOUTH.
Member Since: August 19, 2006 Posts: 13 Comments: 17391
1453. Grothar
The EPAC looks like something wants to start up something


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Quoting Neapolitan:
That may very well be--but a multi-state area considerably larger than NYC itself was affected by yesterday's storms, and in your OP, you referred to the "NE US", not just the city.


My bad I meant NYC sorry man. Have a great Friday!
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Quoting StormTracker2K:


Lightning was the biggest issue in NYC according to the news I saw.

That may very well be--but a multi-state area considerably larger than NYC itself was affected by yesterday's storms, and in your OP, you referred to the "NE US", not just the city.
Member Since: November 8, 2009 Posts: 4 Comments: 14505
Quoting Neapolitan:
Come again? Two people were killed, hundreds of thousands lost power, countless trees and buildings were damaged or destroyed, states of emergency have been declared, more than 400 storm reports (mostly for win) have come in, and suspected tornadoes touched down in several areas.

Overrated? I suppose that's a subjective opinion. But it was quite a bit more than just "five minutes of hard rain"...


Lightning was the biggest issue in NYC according to the news I saw.

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Dr. Masters co-founded wunderground in 1995. He flew with the NOAA Hurricane Hunters from 1986-1990. Co-blogging with him: Bob Henson, @bhensonweather

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