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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From the SPC:

"SUMMARY...SEVERE TSTM WATCH 527 CONTINUES UNTIL 03Z...WITH
APPRECIABLE SHORT-TERM CONCERN FOR WIDESPREAD DAMAGING WINDS INTO
THE GREATER NYC METRO AREA/SOUTHERN NEW ENGLAND AND MUCH OF NJ WITH
AN ONGOING SEVERE MCS/DERECHO. AN ADDITIONAL SEVERE TSTM WATCH MAY
BE NEEDED FOR A PART OF SOUTHEAST NEW ENGLAND INCLUDING RHODE
ISLAND/SOUTHEAST MA."

It was a derecho. Need anymore proof?
Member Since: July 6, 2010 Posts: 113 Comments: 31532
Quoting MAweatherboy1:
So, let's vote...
Was this a derecho?

A. Yes.
B. No.


Negative.
Member Since: Posts: Comments:
Quoting Patrap:
Sorry, I never poll on a Thursday.


I never poll on days ending in "Y"
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1146. ncstorm
I actually posted a statement from NWS in State College, PA that said it was a derecho..
Member Since: August 19, 2006 Posts: 13 Comments: 14599
Quoting Doppler22:

The National Weather Service in State College PA has issued an

* Urban and Small Stream Flood Advisory for...
Adams County...
eastern Cumberland County...
Dauphin County...
Lancaster County...
Lebanon County...
eastern Perry County...
southern Schuylkill County...
York County...

* until 1000 PM EDT...

* at 654 PM EDT Doppler radar showed heavy rain moving into the
area. A quick 1 to 2 inches of rain is possible and could cause some
localized minor flooding in normal poor drainage areas... as well as
ponding on some roads.

* Locations that may experience minor flooding include but are not
limited to... Lebanon... Lancaster... Harrisburg... York and Gettysburg.

Precautionary/preparedness actions...

A Flood Advisory means that although streams and creeks may be
elevated or even rise out of their banks... property damage will be
minimal. Inconveniences can be expected but the flooding will not be
immediately life threatening.


State College or Paternoville?
Member Since: Posts: Comments:
Quoting Patrap:
Sorry, I never poll on a Thursday.

Sorry, forgot about that. You're excused from this one.
Member Since: February 11, 2012 Posts: 82 Comments: 7635
Quoting MAweatherboy1:
So, let's vote...
Was this a derecho?

A. Yes.
B. No.

B
Member Since: Posts: Comments:
The storm just ran through my area on Long Island. A gust or two around 40 mph, some moderate rain, some lightning. Nothing special at all. Can't speak for other areas but it was a dud at my location.
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1141. Patrap
Sorry, I never poll on a Thursday.
Member Since: July 3, 2005 Posts: 421 Comments: 127636
Quoting MAweatherboy1:
So, let's vote...
Was this a derecho?

A. Yes.
B. No.


No.
Member Since: Posts: Comments:
Quoting MAweatherboy1:
So, let's vote...
Was this a derecho?

A. Yes.
B. No.


B.
Member Since: Posts: Comments:
So, let's vote...
Was this a derecho?

A. Yes.
B. No.
Member Since: February 11, 2012 Posts: 82 Comments: 7635
Atleast there is drought relief over some areas that are in Exceptional Drought.
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June 29th storms... Amazing.

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Quoting TropicalAnalystwx13:

The only difference between the two is that, in a derecho, the damaging winds are produced by downbursts produced by severe thunderstorms. Squall line is just straight-line winds.


umm last thing:

Straight-line winds are common with the gust front of a thunderstorm or originate with a downburst from a thunderstorm.

i dont think your analysis is right.
a derecho is just a more extreme squall line
Member Since: February 11, 2012 Posts: 0 Comments: 9721
1134. KEEPEROFTHEGATE (Mod)
it was a line of severe storms thats it nothing more

and its up too the NWS to call it what ever it was and still is

iam out for a bit

back in an hour or so
Member Since: Posts: Comments:
Quoting TropicalAnalystwx13:

The only difference between the two is that, in a derecho, the damaging winds are produced by downbursts produced by severe thunderstorms. Squall line is just straight-line winds.

I think to visualize a Derecho, visualize a Haboob but with rain.
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TROPICAL WEATHER OUTLOOK
NWS NATIONAL HURRICANE CENTER MIAMI FL
500 PM PDT THU JUL 26 2012

FOR THE EASTERN NORTH PACIFIC...EAST OF 140 DEGREES WEST LONGITUDE..

A BROAD LOW PRESSURE AREA IS LOCATED ABOUT 1650 MILES WEST-SOUTHWEST
OF THE SOUTHERN TIP OF BAJA CALIFORNIA. THE ASSOCIATED SHOWER
ACTIVITY IS DISORGANIZED...AND UPPER-LEVEL WINDS ARE BECOMING LESS
CONDUCIVE FOR DEVELOPMENT. THIS SYSTEM HAS A LOW CHANCE...NEAR
0 PERCENT...OF BECOMING A TROPICAL CYCLONE DURING THE NEXT 48 HOURS.

ELSEWHERE...TROPICAL CYCLONE FORMATION IS NOT EXPECTED DURING THE
NEXT 48 HOURS.

$$
FORECASTER BEVEN
Member Since: February 11, 2012 Posts: 82 Comments: 7635

The National Weather Service in State College PA has issued an

* Urban and Small Stream Flood Advisory for...
Adams County...
eastern Cumberland County...
Dauphin County...
Lancaster County...
Lebanon County...
eastern Perry County...
southern Schuylkill County...
York County...

* until 1000 PM EDT...

* at 654 PM EDT Doppler radar showed heavy rain moving into the
area. A quick 1 to 2 inches of rain is possible and could cause some
localized minor flooding in normal poor drainage areas... as well as
ponding on some roads.

* Locations that may experience minor flooding include but are not
limited to... Lebanon... Lancaster... Harrisburg... York and Gettysburg.

Precautionary/preparedness actions...

A Flood Advisory means that although streams and creeks may be
elevated or even rise out of their banks... property damage will be
minimal. Inconveniences can be expected but the flooding will not be
immediately life threatening.
Member Since: Posts: Comments:
When all else fails, do the research. Its not totally cut and dry, and involves quite a bit more than just 58+ mph winds and a straight line- or else they would be far more common-- most every cold front would have one. The SPC page is a great resource about everything that goes into them..

Definition of a derechoA derecho (pronounced similar to "deh-REY-cho" in English, or pronounced phonetically as "") is a widespread, long-lived wind storm that is associated with a band of rapidly moving showers or thunderstorms. Although a derecho can produce destruction similar to that of tornadoes, the damage typically is directed in one direction along a relatively straight swath. As a result, the term "straight-line wind damage" sometimes is used to describe derecho damage. By definition, if the wind damage swath extends more than 240 miles (about 400 kilometers) and includes wind gusts of at least 58 mph (93 km/h) or greater along most of its length, then the event may be classified as a derecho.


Link
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Quoting TropicalAnalystwx13:

The only difference between the two is that, in a derecho, the damaging winds are produced by downbursts produced by severe thunderstorms. Squall line is just straight-line winds.
So the question is this storm line have downbursts? Not challenging, just wondering.
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1127. beell
.
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Day is lonnnnng from over for Ohio Vally.

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Quoting MAweatherboy1:

But then doesn't that make every average severe squall line a derecho?

The only difference between the two is that, in a derecho, the damaging winds are produced by downbursts produced by severe thunderstorms. Squall line is just straight-line winds.
Member Since: July 6, 2010 Posts: 113 Comments: 31532
Produced severe storms along a thousand mile axis which was very impressive. First line never had the sustained winds and duration with said winds to be a derecho in my opinion. Warnings were consistent in the first line for the distance needed, so an argument could be made. Would be way more wind reports in those warned areas though if they were consistent 58 plus.
Member Since: April 18, 2012 Posts: 0 Comments: 2437
ok so here in Stewartstown,PA (SE PA)
wind gusts up to 50mph
Very Very Heavy Rain
Lots of Lightning
Lots of Thunder
Very freaky looking clouds
NOW- waiting for line two in western PA to come over my house later and hoping i still have power
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1122. bappit
Quoting Pocamocca:

So, like the ones who are ostracized by the AGW crowd for voicing an opinion different from there's, it's my turn to feel the heat from everyone for disagreeing in regards to the intensity of our squall line over NYC.

I see how it is...

Just a possibility that people are reacting to the over bearing nature of your posts.
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1121. Patrap
Ring of Fire Derecho


Published on Jun 30, 2012 by akrherz

Timelapse of closest NEXRAD base reflectivity of the 29 June 2012 derecho. The timelapse moves from Davenport, Iowa to Richmond, Virginia over 14 hours.


Member Since: July 3, 2005 Posts: 421 Comments: 127636
Quoting Bluestorm5:
I think we all can agree this is not like June 29th storms.

I can agree to that. June 29 was referred to as a "Super derecho".
Member Since: July 6, 2010 Posts: 113 Comments: 31532
Quoting TropicalAnalystwx13:

If the line has winds over 58 mph, is long-lived, and covers a large area...it's a derecho. There's no debating over that.

But then doesn't that make every average severe squall line a derecho?
Member Since: February 11, 2012 Posts: 82 Comments: 7635
From now on can people not scream Derecho unless the SPC says so officialy? (don't care if it's spelled wrong).
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I think we all can agree this is not like June 29th storms.
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Quoting Bluestorm5:
I'm just not sure this is derecho...

A Derecho is measured by its downdraft winds (which can only/mostly go down, IIRC, by definition)...the rain and normal wind not counted.

I saw my first mega-downburst 2 months ago, and they're something else.
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Quoting MAweatherboy1:

I think this is just a stronger than normal squall line... A typical derecho will feature widespread 80mph winds... This event didn't have much above 70mph.

If the line has winds over 58 mph, is long-lived, and covers a large area...it's a derecho. There's no debating over that.
Member Since: July 6, 2010 Posts: 113 Comments: 31532
1113. Patrap
The Blog needs a massage me tinks,..too wound up over nothing we have control over.

Chablis?
Member Since: July 3, 2005 Posts: 421 Comments: 127636
Quoting TropicalAnalystwx13:

"A derecho is a widespread, long-lived, straight-line windstorm that is associated with a fast-moving band of severe thunderstorms."



What are you not understanding about that?
Sorry, man... I kept changing my opinion of derecho or not.
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Quoting ncstorm:


I keep saying people should not be coming here for life threatening situations..if you want to know if its going to rain..yeah, come on and inquire but when the SPC puts out warnings for a potential derecho, please refer to your local NWS..no on this blog is an expert..NO ONE!

idk...I'd consider Levi an expert.
Member Since: July 6, 2010 Posts: 113 Comments: 31532
Quoting TropicalAnalystwx13:

"A derecho is a widespread, long-lived, straight-line windstorm that is associated with a fast-moving band of severe thunderstorms."



What are you not understanding about that?

I think this is just a stronger than normal squall line... A typical derecho will feature widespread 80mph winds... This event didn't have much above 70mph.
Member Since: February 11, 2012 Posts: 82 Comments: 7635
Quoting beell:


Who's measuring the wind speeds?

Storm chasers, winds reported at the international airports, and doppler radar.
Member Since: July 6, 2010 Posts: 113 Comments: 31532
1108. Patrap
Quoting beell:


Who's measuring the wind speeds?


I believe these folks are usually in a warning.

BULLETIN - EAS ACTIVATION REQUESTED
SEVERE THUNDERSTORM WARNING
NATIONAL WEATHER SERVICE NEW YORK NY
801 PM EDT THU JUL 26 2012

THE NATIONAL WEATHER SERVICE IN UPTON NY HAS ISSUED A

* SEVERE THUNDERSTORM WARNING FOR...
NEW LONDON COUNTY IN SOUTHERN CONNECTICUT...

* UNTIL 930 PM EDT...

* AT 759 PM EDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED A
LINE OF SEVERE THUNDERSTORMS CAPABLE OF PRODUCING DAMAGING WINDS IN
EXCESS OF 60 MPH.
THESE STORMS WERE LOCATED ALONG A LINE EXTENDING
FROM NEW BRITAIN TO DURHAM TO 6 MILES SOUTHWEST OF GUILFORD...AND
MOVING EAST AT 50 MPH.
Member Since: July 3, 2005 Posts: 421 Comments: 127636
Quoting MAweatherboy1:

Definitely overhyped, but not a total bust:



I think this is just a strong thunderstorms today. However, Central PA line still got a chance. Still many reports from that area.
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Quoting Bluestorm5:
What an another hyped "derecho" event... you can't just predicts them.
Please..stop using that word :).Their was only ONE confirmed one that moved over my area and over the mid-west on June 29 unfortunately.So please..
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1105. ncstorm
Quoting Pocamocca:

It's a blog. I'm a blogger. They shouldn't be listening to me. Head the official warnings from the authorities regarding life choices with storms.


I keep saying people should not be coming here for life threatening situations..if you want to know if its going to rain..yeah, come on and inquire but when the SPC puts out warnings for a potential derecho, please refer to your local NWS..no on this blog is an expert..NO ONE!
Member Since: August 19, 2006 Posts: 13 Comments: 14599
Quoting Bluestorm5:
I'm just not sure this is derecho...

"A derecho is a widespread, long-lived, straight-line windstorm that is associated with a fast-moving band of severe thunderstorms."



What are you not understanding about that?
Member Since: July 6, 2010 Posts: 113 Comments: 31532
1103. barbamz
Regardless whether derecho or not: it has been quite impressive watching the liberty cam. I saved some screenshots.





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Nick Wiltgen, weather.com Meteorologist:
Severe weather parameters are still fairly high around Baltimore and DC so storms could yet intensify there.



idk about this, but that what he says.

anyway guys, im out got a big swim meet tomorrow so i probably wont be back till tomorrow afternoon/evening.

have a good night
Member Since: February 11, 2012 Posts: 0 Comments: 9721
Hey guys, is this a derecho or not? I don't think this is derecho IMO.

June 29th


Today
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1100. beell
.
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From the heart of Brooklyn.. (and a nearly 20 year emergency services professional) we have had much of the storm go through at this point. Although it probably meets severe critera, it doesnt really appear to be much more than a B grade summer thunderstorm. Decent amount of wind, pretty significant rain, but a quick mover that appears more bark than bite. I think the June 26/27 event featured storm stops around 60,000 feet in a large mass of cells, the ones that made it here only had a single member over fifty. Perhaps I am off base, but storm tops seem to be the best indicator of intensity here in NYC and these didnt match many of the more significant ones I have experienced.

For some of those posting here, we get severe weather pretty often, including an EF2 in 2007 that literally dropped across from my apartment. The Central Park Microburst a couple of years ago was also very intense, as were the after effects of T/S Irene. I think it might be a false assumption that we dont often see decent severe weather here-- I can assure you we get our five-ten days of decent t-storms each year. Again, I think sometimes the media gets a little excited when circles and cones of doom have NYC in them.
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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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