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Posted at 02:12 PM ET, 06/25/2012

Microburst! Inside the explosive storm that blasted D.C., Md. (Photos/video)


Roof damage to a residential building in Bladensburg, Md. on June 22, 2012. (Billy McNeel/Prince George’s co. Office of Emergency Management)
The setup was simple Friday (June 22) evening. A cold front would clash with a blistering hot and humid air mass parked over the mid-Atlantic and Northeast. The atmosphere had all the fuel it needed to trigger some severe thunderstorms.

Between 7:15 and 8:15 p.m., the atmosphere exploded, and damaging winds, torrential rain, and hail raked a narrow area that spanned from Bethesda, Md. through northern sections of the District into Landover, Md.

Bladensburg, Md was ground zero for the damaging storms where a powerful microburst blasted a residential neighborhood. The National Weather Service (NWS) describes the damage and the winds that occurred:

EXTENSIVE DAMAGE OCCURRED TO BUILDINGS AND TREES. ALONG NEWTON STREET...ROOF DAMAGE WAS SUSTAINED AT AN APARTMENT BUILDING. PIECES OF THE ROOF WERE BLOWN DOWNWIND AND DAMAGED VEHICLES. ADDITIONAL HOMES IN THE AREA SUFFERED ROOF UPLIFT. NUMEROUS TREES WERE UPROOTED...AND MANY LARGE LIMBS WERE SNAPPED. POWER POLES ALSO WERE OBSERVED TO BE LEANING. WIND IN THIS DOWNBURST WAS ESTIMATED TO BE 90 TO 100 MPH.

The storm displaced at least 70 residents according to the American Red Cross. The Prince George’s county Fire Department reported two minor injuries and responded to 235 calls in about 4 hours during and after the storm.

So what is a microburst?

A microburst, defined

A microburst is simply a downward burst or acceleration of strong winds that hit the ground and spread out in all directions, sometimes accelerating further. NWS correctly notes that these winds - 80 to 100 mph or stronger sometimes - are comparable or even more powerful than some tornadoes.


Diagram of a microburst (NOAA)
Meteorologist Bob Ryan offers a bit more color at the WJLA weather blog:

Downbursts happen as the rain and hail generated in a thunderstorm cell begin falling and drag the air toward the ground, cooling the air as the precipitation melts and evaporates. As a result, a falling bubble of cold air that can reach speeds of 100 miles per hour is generated. Then BANG, the racing cold bubble of air hits the ground and causes the damage we saw

A close-up view of Friday’s microburst

The NWS office in Sterling has developed a great explainer page on Friday’s microburst, with a series of helpful doppler radar animations. Here’s a still image of the radar view of the storm from National Airport just a couple minutes before it reached Bladensburg.


Doppler radar view of thunderstorm that produced microburst in Bladensburg, Md. (National Weather Service)

Note the above view is a velocity scan of winds, rather than a display of where the rain is. The NWS provides this explanation of how to interpret this kind of radar image:

The blue arrow represents the downburst (downdraft) heading toward the surface. The red arrow represents the less intense side of the downburst once it reaches the surface, while the larger green arrow is where the most intense “straight-line winds” are accelerating away from where the downburst initially made contact with the ground. The colors represent the horizontal direction at which meteorological targets (rain in this case) are moving, relative to the location of the radar - which is to the south and east of the downburst impact area. Red colors represent air/raindrops moving away from the radar and green represents air/raindrops moving toward the radar. In this image, the brighter the color, the higher the speeds.

Historic microbursts around Washington, D.C.

The term microburst was coined by Ted Fujita, who performed the seminal research on these storms, which included a case study of a particularly severe event that occurred Andrews Air Force Base in 1983. The National Weather Service says winds were clocked at 158 mph.

Microbursts - or macrobursts if they cover a larger region - are fairly common in the metro region during summer.

Last summer, a macroburst ripped through parts of the District and Arlington, downing trees, and knocking out power to more than 40,000 homes.

One of the more dramatic microbursts to affect the region occurred on June 14, 1989. CWG’s Don Lipman described this storm:

[the storm] hit a relatively small portion of Northwest Washington and Bethesda, Md. during the late afternoon rush hour. In a short time, wind gusts (probably downdraft microbursts) estimated at more than 80 miles per hour caused an estimated 28 million dollars in damage and the loss of power to 150,000 homes.

Videos of the June 22, 2012 storm

From Bethesda

Uploaded by ovechkinsgoal

From Mt. Ranier

Uploaded by jgroves76

Photos of the storm

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By  |  02:12 PM ET, 06/25/2012

Categories:  Latest, Recaps, Thunderstorms

 
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