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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1199. Patrap
Quoting redwagon:

If you google or wiki Straight-line Winds, you get directed to Derecho or Microburst.

That's what I'm saying about losing the definition of SLWs. Winds that blow parallel to the earth's surface are generally... straight. Most if not all winds blow straight. What I'm asking is why do weather reports include chances of 'straight line winds' when the damage from wind dropping straight down is far different than wind blowing down the street?




I've flown a few Micro burst sims in a 737 Sim and itsa not phun to fly against ones Experience, but in a micro during climb out and wheels up ,you get a Updraft wind that makes one want to nose down, then when into the downdraft column, your hit in a nose down config with a lets say, 70 Knot downwind and if you dont go Full Power to the Firewall...and full UP on the Joystick/yoke,

Your going down.

That happened here 30 years ago this month.

Pan_Am_Flight_759

The National Transportation Safety Board determined that the probable cause of the accident was the aircraft's encounter with a microburst-induced wind shear during the liftoff, which imposed a downdraft and a decreasing headwind, the effects of which the pilot would have had difficulty recognizing and reacting to in time for the aircraft's descent to be stopped before its impact with trees. Contributing to the accident was the limited capability of then-current wind shear detection technology; this, along with the similar crash of Delta Air Lines Flight 191 three years later led to the development of the airborne wind shear detection and alert system and the mandate by the U.S. Federal Aviation Administration have on-board windshear detection systems installed by 1993.
Member Since: July 3, 2005 Posts: 421 Comments: 127664
Quoting washingtonian115:
Wonderful...now watch it be upgraded to red..Highs are suppose to be in the mid 90's and humidity is suppose to be there as well.Only going to help fuel these storms.

That's for tonight... They took the Mod. risk away... This is tomorrow:

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Quoting MAweatherboy1:
New SPC outlook:

Wonderful...now watch it be upgraded to red..Highs are suppose to be in the mid 90's and humidity is suppose to be there as well.Only going to help fuel these storms.
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Quoting TropicalAnalystwx13:
Kori, you wanted an active West Pacific. Here it is...

93W:



94W:



95W:



I was noticing that too. It's about time!
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Quoting washingtonian115:
I know people will call me nutty..But for some odd reason I feel as though what we're not paying for in the tropics we're paying for on land o_0?.Is their some strange correlation with that?.


I don't know, but that's definitely been the norm the last couple years.
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Quoting Patrap:


A Microburst is anything but a straight Line wind.

..and I've sadly seen what they can do to a 727 fully Loaded.




If you google or wiki Straight-line Winds, you get directed to Derecho or Microburst.

That's what I'm saying about losing the definition of SLWs. Winds that blow parallel to the earth's surface are generally... straight. Most if not all winds blow straight. What I'm asking is why do weather reports include chances of 'straight line winds' when the damage from wind dropping straight down is far different than wind blowing down the street?
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SPC just confirmed this is an ongoing derecho.
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New SPC outlook:

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Quoting TropicalAnalystwx13:
Kori, you wanted an active West Pacific. Here it is...

93W:



94W:



95W:



95W looks the most likely to develop. Models are hinting of a possible super typhoon this time next week
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GFS shows a 972 millibar storm in 192 hours. West Pacific, of course.

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1189. barbamz
State of Emergency declared for all of Chemung County
By: Web Staff
It moved fast, but left some serious damage in its wake. A line of severe storms swept through the Southern Tier Thursday afternoon. Our Bill Mich joined us from Elmira, where much of the worst damage was reported.

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More for Kori.



(1) THE AREA OF CONVECTION PREVIOUSLY LOCATED NEAR 7.3N 131.6E
IS NOW LOCATED NEAR 11.1N 130.9E, APPROXIMATELY 315 NM NORTHWEST OF
PALAU. ANIMATED MULTISPECTRAL SATELLITE IMAGERY SHOWS CONVECTION HAS
BEEN SLOWLY COALESCING AROUND A BROAD UNORGANIZED LOW LEVEL
CIRCULATION CENTER (LLCC). A 260022Z ASCAT PASS INDICATED THE LLCC
HAS MOVED NORTHWARD OVER THE PAST 12 HOURS WITH WINDS ALONG THE
SOUTHEASTERN QUADRANT BETWEEN 10 AND 15 KNOTS. THE LLCC REMAINS
LOCATED WITHIN THE MONSOON TROUGH, WITH THE TROUGH EXTENDING TO THE
SOUTHWEST OF PALAU. UPPER LEVEL ANALYSIS INDICATES THE LLCC IS
MOVING TOWARDS AN AXIS OF MODERATE VERTICAL WIND SHEAR (15-20 KNOTS)
WITH A TROPICAL UPPER TROPOSPHERIC TROUGH LOCATED TO THE NORTHEAST
OF GUAM IS BEGINNING TO INCREASE EASTERLY OUTFLOW. NUMERICAL MODEL
GUIDANCE SUGGESTS A GRADUAL CONSOLIDATION OF THIS LLCC AS IT TRACKS
IN A GENERALLY POLEWARD DIRECTION OVER THE NEXT FEW DAYS. SEA
SURFACE TEMPERATURES (SSTS) IN THE AREA ARE FAVORABLE FOR TROPICAL
CYCLOGENESIS RANGING FROM 28-30 DEGREES CELSIUS. MAXIMUM SUSTAINED
SURFACE WINDS ARE ESTIMATED AT 10 TO 15 KNOTS. MINIMUM SEA LEVEL
PRESSURE IS ESTIMATED TO BE NEAR 1008 MB. BASED ON THE PERSISTENT
CONVECTION, WARM SSTS, AND INCREASING OUTFLOW CHANNELS, THE
POTENTIAL FOR THE DEVELOPMENT OF A SIGNIFICANT TROPICAL CYCLONE
WITHIN THE NEXT 24 HOURS IS UPGRADED TO MEDIUM.

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So, how about that storm in the atlantic...

Or did you hear Al Gores latestest comment?

JK, JK !!
Member Since: August 30, 2008 Posts: 0 Comments: 173
Kori, you wanted an active West Pacific. Here it is...

93W:



94W:



95W:

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Quoting TropicalAnalystwx13:

Yeah...I tried changing the subject to tropical weather a second ago lol.
LOL, I know. I think it's in everybody to try to corrects people's mistakes. Anyway, SAL still taking control of Atlantic?
Member Since: August 1, 2011 Posts: 28 Comments: 7912
1184. beell
.
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Quoting barbamz:
Stunning photos from todays, ehrrm, weather event:
http://gothamist.com/2012/07/26/storm_photos.php# photo-1


Great pics...
Member Since: August 30, 2008 Posts: 0 Comments: 173
Quoting Bluestorm5:

Whoops. Thought you said the most. My bad. I'm done discussing it before it get ugly, lol.

Yeah...I tried changing the subject to tropical weather a second ago lol.
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1181. Patrap
Quoting washingtonian115:
I know people will call me nutty..But for some odd reason I feel as though what we're not paying for in the tropics we're paying for on land o_0?.Is their some strange correlation with that?.


Indeed, a Warmer, Moister overall environment that is producing Stronger T-storms as more heat in the System drives more severe weather.
Member Since: July 3, 2005 Posts: 421 Comments: 127664
Quoting TropicalAnalystwx13:

Read my comment again. "One of the most...".

Whoops. Thought you said the most. My bad. I'm done discussing it before it get ugly, lol.
Member Since: August 1, 2011 Posts: 28 Comments: 7912
Quoting Bluestorm5:


"While not the most intense or long-lived event ever observed, the June 29, 2012 Ohio Valley / Mid Atlantic derecho was noteworthy in producing the all-time highest recorded June or July wind gusts at several official observing sites along its path (Fort Wayne, Indiana, Zanesville, Ohio, and Huntington, West Virgina), in addition to widespread, significant wind damage." It's just known for many people in path.

From SPC: Link

Read my comment again. "One of the most...".
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Totals of reports will pushing the five hundreds by ten. Active day. Wonder if the huge line will break down quickly after sundown. Very top line of severe wind reports in NY goes, in a consistent line, for a very long way with no breaks. That was a very strong area today, any one know of injuries in the confirmed tornadoes? SPC said there would be a couple tornadoes and there were two. Looked like that wouldn't be the case in the beginning of this event. SPC did a really great job.
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Link

This article talks about damage in Elmira, NY.
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1176. beell
.
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I know people will call me nutty..But for some odd reason I feel as though what we're not paying for in the tropics we're paying for on land o_0?.Is their some strange correlation with that?.
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Quoting TropicalAnalystwx13:
June 29, 2012's derecho was not a typical one. It was one of the most destructive and intense in North American history. We cannot use that as a bar.


"While not the most intense or long-lived event ever observed, the June 29, 2012 Ohio Valley / Mid Atlantic derecho was noteworthy in producing the all-time highest recorded June or July wind gusts at several official observing sites along its path (Fort Wayne, Indiana, Zanesville, Ohio, and Huntington, West Virgina), in addition to widespread, significant wind damage." It's just known for many people in path.

From SPC: Link
Member Since: August 1, 2011 Posts: 28 Comments: 7912
1173. Patrap
Quoting redwagon:

I think we're also losing the definition of 'straight-line winds'.

Straight-line Winds, maybe because of how they were depicted on aviation sfc analysis charts, meant 'Air dropping straight down real fast (>60mph)' and became known as aviation became common. SLWs were a major cause of planes crashing on takeoff for (until then) no apparent cause.

Microbursts and downdrafts are other terms used for this phenomenon.


A Microburst is anything but a straight Line wind.

..and I've sadly seen what they can do to a 727 fully Loaded.



Member Since: July 3, 2005 Posts: 421 Comments: 127664
Quoting KoritheMan:


*sigh*

Lol Kori.

----------------

The average date for the 5th named storm is August 31st, and the average date for the 2nd hurricane is August 28th; the average date for the 1st major hurricane is September 4th.

I think we'll eclipse all of those.
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1171. barbamz
Stunning photos from todays, ehrrm, weather event:
http://gothamist.com/2012/07/26/storm_photos.php# photo-1
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Quoting washingtonian115:
First of all when that Derecho was blowing across my area we constantly had winds of 70+mph.It reached 74mph officially at Reagan National airport.In some places people got sustained 80-90mph winds.Some people reported gust of 45mph for only a few seconds..
Member Since: August 1, 2011 Posts: 28 Comments: 7912
June 29, 2012's derecho was not a typical one. It was one of the most destructive and intense in North American history. We cannot use that as a bar.
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Quoting TropicalAnalystwx13:

Derecho (Pronounced day-RAY-cho), a widespread and usually fast-moving windstorm associated with convection. Derechos include any family of downburst clusters produced by an extratropical MCS, and can produce damaging straight-line winds over areas hundreds of miles long and more than 100 miles across.


*sigh*
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First of all when that Derecho was blowing across my area we constantly had winds of 70 mph.It reached 74mph officially at Reagan National airport.In some places people got sustained 80-90mph winds.Some people reported gust of 45mph for only a few seconds in this event..
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Quoting AussieStorm:

I don't give a rats. It's a storm line as part of a cold front.

I think we're also losing the definition of 'straight-line winds'.

Straight-line Winds, maybe because of how they were depicted on aviation sfc analysis charts, meant 'Air dropping straight down real fast (>60mph)' and became known as aviation became common. SLWs were a major cause of planes crashing on takeoff for (until then) no apparent cause.

Microbursts and downdrafts are other terms used for this phenomenon.
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Quoting KoritheMan:


There is nothing in the official terminology of a derecho that cites downbursts as a deciding factor.

Derecho (Pronounced day-RAY-cho), a widespread and usually fast-moving windstorm associated with convection. Derechos include any family of downburst clusters produced by an extratropical MCS, and can produce damaging straight-line winds over areas hundreds of miles long and more than 100 miles across.
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One more radar picture of derecho and I'm done using the word. Promise ;) Only 36 hours after July 19th derecho, ANOTHER derecho slammed into St. Louis in morning of July 21st, although it was still developing. I was sleeping that time, but I remember the wet ground that morning. This derecho went on to wreck rest of Ohio Valley.

Member Since: August 1, 2011 Posts: 28 Comments: 7912
1162. beell
.
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Quoting TropicalAnalystwx13:

Squall lines can persist for several hours. That doesn't make them a derecho.


Squall lines typically are not bow-shaped.
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The SPC will post a new convective outlook in 20 minutes... We'll see what wording they use.
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1159. Patrap
.." They tried to make me call it a Derecho,
but I said, No, No, No..
Member Since: July 3, 2005 Posts: 421 Comments: 127664
Quoting TropicalAnalystwx13:

Squall lines can persist for several hours. That doesn't make them a derecho.


There is nothing in the official terminology of a derecho that cites downbursts as a deciding factor.
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1157. beell
.
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Quoting KoritheMan:


Exactly. Longevity is the determining factor, not downbursts.

Squall lines can persist for several hours. That doesn't make them a derecho.
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"Was it a Derecho"..no..no..and more NO!.

You all take that definition that someone posted on the last page and save it for future events.
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1154. Patrap
Member Since: July 3, 2005 Posts: 421 Comments: 127664
Quoting MAweatherboy1:
So, let's vote...
Was this a derecho?

A. Yes.
B. No.

Probably not
Member Since: February 13, 2012 Posts: 11 Comments: 3659
The derecho that I went through on July 19th 2006 in Saint Louis... the one with 90-100 mph winds.

Member Since: August 1, 2011 Posts: 28 Comments: 7912
Quoting GeorgiaStormz:


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


Exactly. Longevity is the determining factor, not downbursts.
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Quoting MAweatherboy1:
So, let's vote...
Was this a derecho?

A. Yes.
B. No.

I don't give a rats. It's a storm line as part of a cold front.
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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?
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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.