Wednesday, March 15, 2006

Arctic Flows and Floes

A complex low pressure area stretching from near the mouth of the St. Lawrence River to Greenland is helping to funnel Arctic air down the entire East Coast today. In the Washington DC area, however, strong winds last night under a bright full moon kept the official low from dropping below 40&deg. A few miles outside the Beltway here at Afternoon Blog Central, the low was 38°.

This afternoon, temperatures have risen into the 50s, but the northwesterly wind gusting as high as 40 mph has quite a bite to it. The strong winds and low humidity have prompted a red flag warning for potentially dangerous fire weather conditions. (Note to Ft. Belvoir: Yes, it's extremely dry, but your dewpoint readings have lately been running about 10° or more lower than your neighboring reporting locations. It might be time to check the robo-observer.)

Surface weather map at 1pm today from HPC/NCEP/NWS

Attention now shifts to the low pressure area making its way eastward from near the corner of Colorado, Nebraska, and Kansas. As it passes south of our area, it brings the likelihood of some precipitation late tomorrow night or Friday morning. The latest model run this afternoon is weakening the storm circulation as it approaches the coast, and the precipitation is having a hard time making it over the mountains. The temperatures at upper levels, however, are favorable for at least some snow to fall, although the prospects for accumulation are limited. This is somewhat at odds with the stronger results in the morning model runs, so the situation bears watching, especially for the Friday AM rush hour.

Tonight and Tomorrow

For tonight, winds will diminish somewhat; lows under mainly clear skies will be in the low to mid 30s in the city, with some upper 20s in the colder 'burbs. Tomorrow will be sunny with highs around 55.

Climate Notes

An article in today's NY Times describes the failure of Arctic sea ice to re-form this winter to its normal extent. This is leading to predictions of record-breaking areas of open water this summer.

Meanwhile, a report from the Earth Institute at Columbia University analyzes the history of Scandinavian ice sheet melting during the end of the last ice age. The joint research by scientists from Columbia, Oregon State, and 8 European institutes found that there was an intermittent pattern of ice accumulation and melting as temperatures warmed, eventually leading to a rapid disintegration of the ice sheet once temperatures warmed enough.

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