Tuesday, July 26, 2005
It's the Heat, Stupid
Dan Stillman @ 11:03 PM
Just in case you hadn't noticed that it's hot outside, an excessive heat warning issued by the National Weather Service remains in effect through 8 p.m. this evening. Talk about stating the obvious.I think today will be even warmer than yesterday thanks to downsloping winds from the west (see explanation below). Look for highs from 96 to 101, with the heat index upwards of 105.
Don't be surprised to see the heat warning followed by severe thunderstorm watches and warnings. The Storm Prediction Center has us just inside their slight risk area for severe thunderstorms (see picture at right). Thunderstorms are possible from around 5 p.m. onward today, and could linger into the overnight hours. The cold front touching off these storms will usher in some relief -- highs only in the low-to-mid-80s -- for the rest of the week and weekend. However, the front may also stall out just to our south, giving us decent odds for showers and storms throughout the period.
Yesterday
For all the hoopla, yesterday's heat wasn't all that unusual for Washington in late July. Highs reached 97 at National and 94 at Dulles and BWI. There were the usual heat-related problems however. As of about 10:45 p.m. last night, more than 10,000 Pepco customers in the District and Montgomery and Prince George's counties were without power. Around the same time, Dominion reported just under 800 customers out in Northern Virginia. The Washington Post has this summary of the power woes. Metro riders and anyone who works outside weren't too happy in the heat, either.
A Warm Wind From the West
In my forecast above, I mention "downsloping" winds from the west as a reason today could be even warmer than yesterday. Here's what I'm talking about. Westerly winds blow air down the Appalachian Mountains and into the Washington area. Because pressure increases with decreasing height, this air is compressed as it descends. That causes the air molecules to bounce around faster, making the air warmer. Santa Ana winds have a similar but usually stronger effect in the Los Angeles area.
Hyping the Heat
Not that you need proof that local TV stations like to play up weather extremes ... but check out this tveyes transcript of Channel 4's newscast at 5 p.m. on Monday. I count 12 "heat" references. Thanks to dcrtv.com for spotting this one.
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