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Delightfully Dry ... and a Weekend Worth the Wait

Dan Stillman @ 11:20 PM

The dry air that filtered in during the afternoon yesterday will dominate today, giving the DC area its finest day in quite a while. We'll take one step backward tomorrow, but the outlook for Friday and the weekend more than makes up for the temporary setback.


Nice Day StampSimply superb. With high pressure in control, a gorgeous day is on tap. The high temperature could slightly exceed our criteria for awarding the Nice Day Stamp, but with dewpoints this low (upper 50s to near 60) I couldn't resist. Here's all you really need to know about today's forecast:
  • Sunny
  • Highs 85-88
  • Very low humidity
  • Tonight: lows in the upper 60s in town, low 60s in the burbs


Forecast Confidence: Medium-HighIncreasing humidity ... Chance of PM storms. After sunny skies to start the morning, high pressure drifts far enough offshore to allow encroachment of low pressure that will be developing along an approaching cool front. The result will be increasing clouds and a 30% chance of afternoon or evening showers and thunderstorms. Highs should be in the mid 80s. Overnight, a continued chance of storms early, then clearing skies toward dawn. Lows near 70.

Friday and the Weekend

Forecast Confidence: HighAwesome in August. On Monday, Jason proposed two possible scenarios for this time period: clearing and dry, or humid with PM showers/storms. I can now say with relatively high confidence that we are looking good for door #1 -- spectacularly clear and dry. Northerly to westerly flow ahead of a large region of high pressure building in from Canada should give us abundant sunshine, low humidity, and highs only in the low-to-mid 80s. Overnight lows? ... low-to-mid 60s in town, mid 50s to near 60 in the burbs. Bring it on!

Local Scientists Track Air Pollution

Aura satelliteOur friend Howard Bernstein over at Channel 9 had this recent story (make sure to play the related video) on a project by NASA and Howard University to verify the accuracy of satellite measurements of air pollution indicators.

In the midst of our recent heat wave, scientists headed out to a sunny open field in order to launch a weather balloon full of instruments that measure temperature, humidity, ozone levels and other variables. The balloon launch was timed to coincide with the overpass of NASA's Aura satellite, which makes similar observations from space, so that the satellite measurements could be compared with those recorded by instruments on the balloon that are already known to be reliable.

The ability to accurately measure such quantities from space could lead to improved monitoring and prediction of air quality. Read more about the project here.

Pictured: Artist's rendition of Aura satellite, courtesy NASA.

Hurricane Forecast Downgraded Slightly

As Steve mentioned yesterday, NOAA has reduced the number of named storms predicted to form during the current tropical season from 13-16 to 12-15, and the number of hurricanes expected from 8-10 to 7-9. These numbers still correspond to what is considered above-normal activity.

Tropical expert Jeff Masters summarized the reasons for the decrease quite well in his blog entry yesterday at Weather Underground:
  • Cooler-than-expected Atlantic sea surface temperatures.
  • Higher-than-average surface pressures.
  • Quicker-than-expected transition away from La Nina conditions, resulting in stronger wind shear.
  • Lack of a persistent upper-level area of high pressure over the eastern U.S. and western North Atlantic to steer storms toward the warmer south Atlantic and Gulf of Mexico waters.
Thus far this season there have only been three tropical storms in the Atlantic, none of which have developed into hurricanes, compared to the nine named storms that had formed by this time last year.

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