Saturday Evening Thunderstorms in Washington
I was planning on going out to take photos on Saturday for much of last week, primarily because it looked like it was going to be a quiet evening (oops!). By late afternoon it was apparent that storms to the west would likely make it into the area, but I was still eager to go out and get some new shots. Since I'm always on foot when photographing the area, I decided to stage around the Lincoln Memorial where I could take refuge from rain as needed. Given that it was a summer weekend I was certainly not alone.
Continue reading for more photos and storm commentary...
By late afternoon it was increasingly apparent that storms which formed off to the west would make it into the area, even though most previous forecasts (including those here) discounted the chance of storms on Saturday. The thinking had been that with the D.C. area so far away from a cold front -- which was approaching from the west but on Saturday had only made it as far east as the Ohio Valley -- that any storms would likely fall apart upon reaching the region.
As it turned out, the lift in the atmosphere provided by a pre-frontal trough (an elongated area of low pressure out ahead of a cold front), which itself was created by an outflow boundary (a boundary separating thunderstorm-cooled from surrounding air, along which more thunderstorms sometimes form), in combination with the instability caused by the day's sun and heat, were enough to keep the storms going all the way through the metro area.
When I arrived on the mall just before 7 p.m., thunderstorms were approaching from the west and northwest and the sky was rather murky with just a few spots of blue. My original plan was to cross Memorial Bridge and photograph D.C. from the Virginia riverbank at dusk, but the weather had another idea.
The first 15-20 minutes on the mall were rather calm as a noticeable gust front, the leading edge of gusty winds ahead of approaching thunderstorms, descended upon the city. Winds were steady from the south and it was still quite warm after temperatures rose into the 90s earlier in the day. People began to notice that there was a storm coming and several stopped to take pictures of the cloud mass spreading into the city.
Around 7:20 p.m. (see live tweet just prior), a ragged gust front was moving into D.C. along a line of thunderstorms that produced isolated strong winds. Though Saturday's storms were only sporadically disruptive, the front-end gusts were strong with several bursts (probably 30 mph and higher) even in the weaker section of the line that passed over the Mall. Several of these gusts were able to kick up sizeable amounts of dust along the Lincoln Memorial Reflecting Pool.
A period of moderate to briefly heavy rain pushed through and sent everyone still outside looking for cover. The previously packed National Mall was left deserted.
Additional storms strengthened to the southwest and moved in behind the first line. As I stubbornly began my walk across Memorial Bridge trying to stay to my original plan, several cloud-to-ground lightning strikes in the distance made me turn back. With the strikes still a fair way off I decided to stop for a lightning photo -- a single cloud-to-ground strike is seen in the first photo of this post.
I spent the rest of the second storm sitting on the ledge of the Lincoln Memorial with at least a hundred others seeking cover or sky-watching. The most intense part of the second storm passed south of the Mall, so I stowed my camera rather than test the National Park Service security and enjoyed the show.
Rainfall for the evening totaled .07" at National Airport, pushing this July (now at .89" total) away from the driest-ever reading of .82" in 1871. This July now stands as the second driest ever for D.C. Next up on the list: 0.93" in 1966, 1.01" in 1999 and 1.05" in 1957. Though more rain chances are in the forecast through the month's final days.
| July 27, 2009; 11:10 AM ET
Categories: Photography, Recaps, Thunderstorms
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