wpostServer: http://css.washingtonpost.com/wpost

The Post Most: Local

Posted at 03:35 PM ET, 07/05/2011

NOAA: Sunday’s D.C., Arlington storm a “macroburst”


GOES-13 satellite image of the thunderstorm complex that impacted Northern Virginia, Montgomery county, and the District Sunday. (NOAA Environmental Visualization Laboratory)

The severe thunderstorm that ripped through Arlington and the District Sunday evening was truly explosive. The image above shows the incredible structure of the storm as it developed over Fairfax county. The effervescent cloud popping out of the image is a classic example of an overshooting thunderstorm top - penetrating 50,000+ feet into the atmosphere.

NOAA’s Environmental Visualization Laboratory featured the image on its website today, describing it accordingly:

A violent storm lashed northern Virginia Sunday evening, toppling trees and powerlines. Arlington, VA bore the brunt of the storm where downed trees smashed cars and fell into homes. The National Weather Service estimates winds were between 60 to 70 miles per hour at the height of the storm. The National Weather Service classified the storm as a macro burst, a downward burst of strong winds that hit the ground and spread damage in all directions up to 2.5 miles in mere minutes. This image from the GOES East satellite at 2345Z [7:45 p.m. local time] on July 3, 2011 shows the burst forming.

The cluster of thunderstorms formed as hot and very humid air collided with a cold front pushing southeast. The atmosphere was full of energy - or, in meteorological jargon CAPE (convective available potential energy). The billowing thunderstorm over Fairfax county (in the image) released a chunk of that energy in the violent downburst over Arlington and D.C. (particularly around Dupont Circle and Columbia Heights).

You may have heard damaging thunderstorms in the region described as “microbursts” in the past.

What’s the difference between a microburst and a macroburst? Not much.

Technically, a microburst requires a downdraft of 4 km (2.5 miles) or less whereas a macroburst requires a downdraft of greater than 4 km. Given the extent of the high winds from Sunday’s thunderstorm - this was probably a low-end macroburst.

Additional links:

Violent storm sweeps through area, kills one | Storm video
Pics of trees down & damage: D.C. @ 3rd & I, NE; Arlington @ Old Dominion Dr; Dupont Circle; D.C. @ 10th St. NW; D.C. @ P St. NW; Storm clouds over the Potomac(from near Old Town Alexandria); More damage pics from Arlington (from @bslilly via Twitter)

By  |  03:35 PM ET, 07/05/2011

Categories:  Thunderstorms, Latest

 
Read what others are saying
     

    © 2011 The Washington Post Company