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Posted at 11:30 AM ET, 08/13/2010

D.C.'s scorching summer inciting storms

By Jason Samenow

* A welcome break from the heat and storms: Full Forecast | NatCast *

Thunderstorms tear through the D.C. metro region the morning of August 12, 2010. Radar loop courtesy IMAP.

Everyone knows this summer has been really, really hot (the hottest on record to date) and we've talked about heat records (here, here, here and here) incessantly. But the emergent weather story of summer 2010 is the multiple episodes of fierce thunderstorms (previous recaps here and here) that have ripped through the region taking down untold numbers of trees and generating power outage misery, particularly in Montgomery county.

Are the heat and the storms related?

You bet.

Although the jet stream has been positioned well to our north for much of the summer - enabling a persistent flow of hot and humid air from the south and west, as we've transitioned towards the second half of the summer, said jet stream has taken more excursions southward (see the jet stream position yesterday in the graphic below).

Image of winds about 20,000 feet high midday yesterday (August 12, 2010). The area coinciding with the two black lines of equal pressure (588, 582) approximate the position of the jet stream (where the winds are strongest). Note the dip over the eastern third of the U.S. Also see the wiggle right over central Maryland -- which was a small energetic disturbance that helped to intensify thunderstorm activity. Image courtesy NOAA.

These recent dips in the jet stream have placed the metro region in the battle ground between sometimes record breaking heat and drier, cooler air to the north. Severe thunderstorms have thus developed here and what they've left behind has in some places resembled a war zone.

Instances of wind damage from the three thunderstorm outbreaks this summer. Maps courtesy NOAA's Storm Prediction Center.

Also, note the high temperatures on the afternoons before all three of these thunderstorm events: 99 on July 25, 95 on Aug. 5, and 97 on Aug 11 (prior to the morning of Aug 12). That the thunderstorms packed a punch in this hot air is simply not a mere coincidence...

By Jason Samenow  | August 13, 2010; 11:30 AM ET
Categories:  Thunderstorms  
Save & Share:  Send E-mail   Facebook   Twitter   Digg   Yahoo Buzz   StumbleUpon   Technorati   Google Buzz   Previous: Forecast: Weather less scary for Friday the 13th
Next: How to cope with the heat: Tell a joke


This is interesting. I suspected a correlation between the heat and storms. My question is directed at what lies ahead for the rest of the summer. Are we due for more extreme heat and therefore more extreme storms? Never have I thought I would enjoy such a marine layer on an August friday, but it is delightful outside today...

Posted by: authorofpoetry | August 13, 2010 12:09 PM | Report abuse


Good news is that I'm not seeing indications of record heat for the next week or so. However, temperatures will still look to be above normal and we may have a cold frontal passage or two that could ignite storms. Will they be severe? It's hard to say at this point.

Posted by: Jason-CapitalWeatherGang | August 13, 2010 12:25 PM | Report abuse


Posted by: platinumforests | August 13, 2010 12:37 PM | Report abuse

I don't suppose there are any below-60 dewpoints in the foreseeable future, eh?

Thought not.

Posted by: HenryFPotter | August 13, 2010 1:07 PM | Report abuse

CWG, got two things for you, apologize if you already covered them. But why did we get hammered in Moco Thursday before 7 a.m. by a severe storm of Biblical proporations? Isn't that extremely unusual?
And why do we seem to have so many "Dopplar indicated" tornadoe warnings, that later are not confirmed by ground obersvations? Is Dopplar overly sensitive or is the NWS overly cautious in issuing warnings these days?

Posted by: VikingRider | August 13, 2010 1:25 PM | Report abuse

VikingRider, there was a post yesterday covering the morning storms. Re: dopper... I'd say it is both sensitive (which is a good thin) and maybe the NWS is a little extra cautious in a region like this that is so heavily populated. You do have to keep in mind the radar scans are above the surface so you can get a tornadic signature at that level without actually getting a tornado. Still an inexact science I guess, but it has come a long way and saved a lot of lives.

Posted by: Ian-CapitalWeatherGang | August 13, 2010 1:32 PM | Report abuse

Perhaps power outage misery can be a thing of the past - if they only bury the wires..

Posted by: ZmanVA | August 13, 2010 1:35 PM | Report abuse

Harkening back to yesterday's WJLA discussion between Gordon Peterson and Doug Hill, Gordon asked Doug if this summer's storms are the flip, or reverse, side of last winter's snowstorms.

Doug said something along the lines of "yeah, you could look at it that way".

Is there scientific evidence and data that indicate climatological extremes begat more extremes over a finite period (e.g. year)?

Or is this year's extreme weather merely a series of coincidental, unrelated events, seasoned with a tablespoonfuls of Ninos/Ninas?

Posted by: JerryFloyd1 | August 13, 2010 1:47 PM | Report abuse

I saw the discussion and I interpreted him to say it was the flip in terms of types of storms. He seemed to resist making any connection between the two though. My impression was that he thought it was just happenstance that the extemes came in the same year.

Posted by: marathoner | August 13, 2010 2:02 PM | Report abuse

@Marathoner, Doug Hill did indeed not say the winter and summer storms are related

Gordon, newsman, that he is, pressed the topic. In doing so, he in effect asked questions that on a lot of people's minds, i.e., are this year's extreme weather a random coincidence? Or is there a coorrelation?

Over the centuries people have had all sorts of fanciful explanations for weather extremes. Now, we live in an era when people seek scientifically based, definitive answers.

Posted by: JerryFloyd1 | August 13, 2010 2:37 PM | Report abuse

Maybe someday you guys can explain why many/most thunderstorms develop east of far NW Montgomery County. For the last three summers that has been the case.

On the 25th we received no rain and yesterday we had none in the morning and very little in the evening storm.

It seems to me that before that storms would develop east of the mountains and come rolling through the panhandle and into Loudoun, the cross the river, and give us a good soaking.

Posted by: MKadyman | August 13, 2010 4:55 PM | Report abuse

Might the wiggle on the pressure plot be the storm itself (presuming a 7AM plot)? Do you have any plots prior in time to see if the wiggle is upstream?

Posted by: eric654 | August 13, 2010 5:01 PM | Report abuse

MKadyman, I would think there is some rainshadowing just east of the Apps from time to time but that's just a hunch.

Posted by: Ian-CapitalWeatherGang | August 13, 2010 5:30 PM | Report abuse


This plot is an analysis from 18z yesterday (8/12/10) just after the storms had come through. I pulled down some previous analyses and the wiggle does show up a little at 12z near the Pa/Oh border--and so the vorticity advection in the downstream direction surely fueled the storm development. See: and scroll down to the bottom to retrieve archived imagery.

Posted by: Jason-CapitalWeatherGang | August 13, 2010 5:32 PM | Report abuse

Thanks for the link. I see what you mean, it's a broader (less sharp) wiggle.

Posted by: eric654 | August 13, 2010 9:11 PM | Report abuse

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