Extreme storms and extreme heat hit the U.S.

By: Dr. Jeff Masters , 5:50 PM GMT on June 30, 2012

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A violent line of organized severe thunderstorms called a derecho swept across the U.S. from Illinois to Virginia on Friday, damaging houses, toppling trees, bringing down power lines. The storms killed six people in Virginia, two in New Jersey, and one in Maryland, and left at least 3.4 million people without power. The thunderstorms in a derecho (from the Spanish phrase for "straight ahead") create violent winds that blow in a straight line. The traditional definition of a derecho is a thunderstorm complex that produces a damaging wind swath of at least 240 miles (about 400 km), featuring a concentrated area of thunderstorm wind gusts exceeding 58 mph (93 km/hr.) A warm weather phenomenon, derechos occur mostly in summer, especially June and July in the Northern Hemisphere. They can occur at any time of the year and occur as frequently at night as in the daylight hours. As seen on our wundermap with the "go back in time" feature turned on, Friday's derecho began near Chicago in the early afternoon, then marched east-southeast, peaking in intensity over Virginia and Washington D.C. on Friday evening. The derecho was unusually intense due to the extreme heat, which helped create an unstable atmosphere with plenty of energy to fuel severe thunderstorms.


Figure 1. Radar image from our wundermap with the "go back in time" feature turned on for 11 pm EDT Friday June 29, 2012, showing the derecho over Washington D.C. and Baltimore. Click on the "hour" button above the wundermap to advance the time by one hour to watch the progress of the derecho across the country.


Figure 2. NOAA's Storm Prediction Center (SPC) logged 871 reports of damaging winds on Friday. Twenty one of these reports were for winds over 80 mph. The highest wind gust was in Oswego, Illinois: 92 mph.



Figure 3. A dramatic change in the weather in Buckeye land: the temperature at Ohio State University in Columbus, Ohio dropped from 97°F to 68° after passage of Friday's derecho. The storm brought a wind gust of 82 mph to campus, and 0.86" of rain.

Historic heat wave topples Dust Bowl-era extreme heat records
A historic heat wave on a scale and intensity not seen in the U.S. since the great heat waves of the 1930s Dust Bowl era set new all-time heat records for at least ten major cities Friday. According to wunderground's weather historian Christopher C. Burt, fifteen of the 303 major cities he maintains records for on the wunderground extremes page have set all-time heat records in the past four days. The only year with more all-time heat records is 1936, when 61 cities set all-time heat records. In 2011, which had the 2nd warmest summer in U.S. history, only ten of the 303 cities set all-time heat records during the entire summer. With the the hottest month of the year (July) still to come, 2012 threatens to rival the great Dust Bowl summer of 1936 for extreme heat.

All-time records for any date tied or broken on Friday:

109° Nashville, TN (old record 107° 7/28/1952
109° Columbia, SC (old record 107° on two previous occasions)
109° Cairo, IL (old record 106° on 8/9/1930)
108° Paducah, KY (ties same on 7/17/1942
106° Chattanooga, TN (ties same on 7/28/1952)
105° Raleigh, NC (ties same on 8/21/2007 and 8/18/1988)
105° Greenville, SC (old record 104° 8/10/2007 although 106° was recorded by the Signal Service in July 1887)
104° Charlotte, NC (ties same on 8/9 and 10/2007 and 9/6/1954)
102° Bristol, TN (ties same on 7/28/1952-this site now known as `Tri-State Airport')
109° Athens, GA. This is just 1° shy of the Georgia state record for June of 110° set at Warrenton in 1959.

All-time state June heat records set Friday:

113° Smyrna, TN (old record 110° in Etowah in June 1936)
109° Cairo, IL (old record 108° in Palestine in June 1954)

Also of note: Atlanta, GA hit 104° (its all-time June record), and just 1° shy of its all-time record of 105° set on 7/17/1980. The forecast for Atlanta on Saturday calls for a high of 105°F, which would tie for the hottest day in the city's history.

Wunderground's weather historian Christopher C. Burt has a new post called The Amazing June Heat Wave of 2012 Part 1: The West and Plains June 23 - 27 summarizing the early portion of this week's historic heat wave. He plans to make a follow-up post on Sunday summarizing the records set on Friday and Saturday.

Relatively quiet in the Atlantic
An area of heavy thunderstorms, associated with an upper level low pressure system, has developed in the Gulf of Mexico along the Texas coast. This disturbance will probably move ashore over Texas before development into a tropical depression can occur, and NHC is giving it a 0% chance of development. The tropical wave approaching the Lesser Antilles (Invest 97L) has dissipated due to dry air, and is no longer a threat. None of the reliable computer models are developing anything during the next seven days.

Jeff Masters

Chicago Shelf (LarrySmit)
Chicago Shelf
Summer Heat (gardner48197)
Summer Heat
Smokey Clouds (LarrySmit)
Asperatus Clouds
Smokey Clouds
And the Sky Opened Up! (webgal)
Much needed thunderstorms came through west-central Illinois late this evening. The lightning was absolutely incredible!
And the Sky Opened Up!

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Quoting ncstorm:
try a heat index of 127..


I walked outside to go get the mail and by the time I got back in, I was soaked from sweat.
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Quoting weatherdogg:


Goldsboro has a temp of 103F, with a 83F dewpoint, yielding a heat index of 131F! 50% humidity above 100F is insane. Link


INSANE!
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802. MZT
Those CAPE values in S.C. are something else. 5000 j/kg could easily produce 100 MPH updrafts. That's the kind of hail you normally associate with midwestern "storm chaser" events.
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Quoting Grothar:


Hey, TA, Doesn't Canada have a 4th of July like we do?

Today is their independence day like July 4 is ours.
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Quoting ncstorm:
try a heat index of 127..



Goldsboro has a temp of 103F, with a 83F dewpoint, yielding a heat index of 131F! 50% humidity above 100F is insane. Link
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Wow such heat ncstorm. 127 is no joke and the humidity, ouch. Could cook an egg outside easily right now. That's some life threatening stuff. And now monster cells are building of the vast instability of the crazy heat. Just lovely, good luck with it looks like you've got awhile before the storms visit you. Hope they don't get much stronger.
Member Since: April 18, 2012 Posts: 0 Comments: 2437
Quoting TropicalAnalystwx13:

Yes it was. July 1, 1867.


Hey, TA, Doesn't Canada have a 4th of July like we do?
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Link

seems to be about 200k without power in chicago
Member Since: February 11, 2012 Posts: 0 Comments: 9724
Quoting GeorgiaStormz:


wait, when did you become fully independent of britain, it wasnt on a july 1st?

Yes it was. July 1, 1867.
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Quoting presslord:
KotG...Happy Canada Day!!


Oh, Canada!
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try a heat index of 127..

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Quoting KEEPEROFTHEGATE:
thanks press
happy independence day to you


wait, when did you become fully independent of britain, it wasnt on a july 1st?
Member Since: February 11, 2012 Posts: 0 Comments: 9724
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Quoting presslord:
KotG...Happy Canada Day!!
thanks press
happy independence day to you
Member Since: July 15, 2006 Posts: 170 Comments: 53487
Quoting WxGeekVA:
Wow... Went to a friends house to help him clean up and I saw at least 9 houses with trees on them, roads blocked by all sorts of stuff, and most intersections had lights out. If you live in an area that has been hard hit by the derecho, please check on neghbors, friends, the elderly, and help them out with cleanup and invite them over if you have power.


wow, we never have anything like that, even in our last serial derecho with 80mph winds that was oriented W-E and moved SE taking forever to leave the area.
Not even in the April 4th derecho last year.

I hope everyone gets power back soon, it is brutal out there.


Our AC stopped working this morning and it is now 89F with 57% humidity inside, and 106F feels lie 1ike 108F outside.
I cant imagine not having power for days
Member Since: February 11, 2012 Posts: 0 Comments: 9724
Wow... Went to a friends house to help him clean up and I saw at least 9 houses with trees on them, roads blocked by all sorts of stuff, and most intersections had lights out. If you live in an area that has been hard hit by the derecho, please check on neghbors, friends, the elderly, and help them out with cleanup and invite them over if you have power.
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Lol at the Cape hole over N GA
Typical GA weather.

Did anything bad happen in chicago?
or did the storm just blow through uneventfully
Member Since: February 11, 2012 Posts: 0 Comments: 9724
Quoting DDR:
Good afternoon
Heavy rain showers in parts of Trinidad this afternoon,typical July weather so far,no hint of el nino as yet.


Good for you there. Let's see if other islands get rain from this wave. If not this one,there are more waves downstream that could bring needed rain. Some heavy thunderstorms have been falling in West interior PR with flood advisories being issued.

Member Since: April 29, 2009 Posts: 75 Comments: 14209
785. DDR
Good afternoon
Heavy rain showers in parts of Trinidad this afternoon,typical July weather so far,no hint of el nino as yet.
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Quoting MZT:
ncstorm, yeah even though the initial advisories this morning were for 20% chance, the met discussion sounded ominous if things begin tipping farther with the instability.

BAM! That line just popped up in minutes


Didnt it though..Our NWS used the word "battlefield" this morning..SPC may have to increase the supercell area to SC..
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783. MZT
ncstorm, yeah even though the initial advisories this morning were for 20% chance, the met discussion sounded ominous if things begin tipping farther with the instability.

BAM! That line just popped up in minutes
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KotG...Happy Canada Day!!
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This one's knocking on my doorstep...

BULLETIN - EAS ACTIVATION REQUESTED
SEVERE THUNDERSTORM WARNING
NATIONAL WEATHER SERVICE TAUNTON MA
ISSUED BY NATIONAL WEATHER SERVICE NEW YORK NY
304 PM EDT SUN JUL 1 2012

THE NATIONAL WEATHER SERVICE IN TAUNTON HAS ISSUED A

* SEVERE THUNDERSTORM WARNING FOR...
SOUTHEASTERN WORCESTER COUNTY IN CENTRAL MASSACHUSETTS...
PROVIDENCE COUNTY IN RHODE ISLAND...
SOUTHWESTERN NORFOLK COUNTY IN EASTERN MASSACHUSETTS...
NORTHEASTERN WINDHAM COUNTY IN NORTHERN CONNECTICUT...

* UNTIL 345 PM EDT...

* AT 301 PM EDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED A
SEVERE THUNDERSTORM CAPABLE OF PRODUCING QUARTER SIZE HAIL...AND
DAMAGING WINDS IN EXCESS OF 60 MPH. THIS STORM WAS LOCATED NEAR
THOMPSON...OR NEAR PUTNAM...AND MOVING EAST AT 30 MPH.

* OTHER LOCATIONS IN THE WARNING INCLUDE BUT ARE NOT LIMITED TO
FOSTER...MILLBURY...BURRILLVILLE...GLOCESTER...SCI TUATE...NORTH
SMITHFIELD...SMITHFIELD...BLACKSTONE...WOONSOCKET. ..CRANSTON...
LINCOLN...JOHNSTON...CUMBERLAND AND NORTH PROVIDENCE

PRECAUTIONARY/PREPAREDNESS ACTIONS...

IN ADDITION TO LARGE HAIL AND DAMAGING WINDS...CONTINUOUS CLOUD TO
GROUND LIGHTNING IS OCCURRING WITH THIS STORM. MOVE INDOORS
IMMEDIATELY! LIGHTNING IS ONE OF NATURES NUMBER ONE KILLERS.
REMEMBER...IF YOU CAN HEAR THUNDER...YOU ARE CLOSE ENOUGH TO BE
STRUCK BY LIGHTNING.

&&

LAT...LON 4203 7145 4175 7144 4188 7197 4204 7200
TIME...MOT...LOC 1904Z 271DEG 27KT 4196 7181

$$

JM
Member Since: February 11, 2012 Posts: 83 Comments: 7725
crazy how this has gone from 0 to 60 just like that..

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778. MZT
Reavencrest station in Charlotte (a few miles east of me) got to a 108 degree max today.

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Member Since: July 15, 2006 Posts: 170 Comments: 53487
Quoting MAweatherboy1:
I feel pretty lucky... Only 84 degrees here :)


As do I, weirdly enough. :)

Orange County Airport
Lat: 30.07 Lon: -93.8 Elev: 13
Last Update on Jul 1, 1:35 pm CDT

Partly Cloudy

86 °F
(30 °C)
Humidity: 70 %
Wind Speed: S 10 MPH
Barometer: 30.07"
Dewpoint: 75 °F (24 °C)
Heat Index: 95 °F (35 °C)
Visibility: 7.00 mi.
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775. MZT
Egads. Is that a bow of storms forming from Columbia to Durham? Looks like that convection on the NC/VA border is forming a tail off to the SW down into SC
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Member Since: July 15, 2006 Posts: 170 Comments: 53487
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Quoting PackManWx:

What do the red hashmarks mean over areas of NC? That's where I live


hatched region
likly super cell development
Member Since: July 15, 2006 Posts: 170 Comments: 53487
Quoting Tribucanes:
Is this going to turn into a tornado risk for SC/NC? Way more discreet cells here and they are firing fast when they do. Wide swath of mean weather coming today. I'm really hoping that doesn't develop to a full derecho, but if the winds in Chicago are any indication then it's going to be a long day for a lot of people. Couple hundred reports possible in the Carolina's today alone. Is this just an exception these past few days or are these unrelenting heat waves going to supercharge storms for the coming weeks or even months?


I've always grown up with the thinking that the hotter it is in summer, the more severe the afternoon storms would be..I just hope people that are out this sunday afternoon are aware of whats transpiring..
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July starts and the MDR looks dull.
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Is this going to turn into a tornado risk for SC/NC? Way more discreet cells here and they are firing fast when they do. Wide swath of mean weather coming today. I'm really hoping that doesn't develop to a full derecho, but if the winds in Chicago are any indication then it's going to be a long day for a lot of people. Couple hundred reports possible in the Carolina's today alone. Is this just an exception these past few days or are these unrelenting heat waves going to supercharge storms for the coming weeks or even months?
Member Since: April 18, 2012 Posts: 0 Comments: 2437
763. MZT
106 degress in Sumter, S.C. right now. Whew!

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762. Skyepony (Mod)
1250 PM TSTM WND DMG NORTHLAKE 41.91N 87.90W
07/01/2012 COOK IL TRAINED SPOTTER

FLIPPED SHED IN HOME DEPOT PARKING LOT

Chicago storm reports.
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Quoting PackManWx:

What do the red hashmarks mean over areas of NC? That's where I live

It means storms in the area could produce significant winds in excess of 65 knots (75 mph).
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Quoting KEEPEROFTHEGATE:

What do the red hashmarks mean over areas of NC? That's where I live
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Here we go again, can you say five hundred plus SW reports possible today. Hope people aren't tuned out for this one. Look for moderate warning to be upgraded to for areas in the way of these ugly storms today. Derecho must make it 240 miles to qualify as one, lets hope this line weakens before this. No classical bow to it yet either. Storms firing behind this line today could produce some ugliness too.
Member Since: April 18, 2012 Posts: 0 Comments: 2437
Member Since: July 15, 2006 Posts: 170 Comments: 53487
Another Derecho in the making.
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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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