High wind watch for the region yet again
Since December, the winds around the D.C. metro region have seemed relentless - and more persistently disruptive than I can ever remember. Less than a week after our last significant wind event, the National Weather Service has issued a high wind watch for Friday for between 11 a.m. and 7 p.m. The watch includes most of the metro region, but excludes some the southern areas including southern Fauquier, Stafford, Charles, Calvert and St. Mary's counties. But gusty winds to 50 mph are still possible in areas outside the watch.
Here are some of the key points from the watch:
* Sustained winds of between 20 to 30 mph, with gusts to 50 to 60 mph are likely
* Possible impacts: Power outages and downed trees and large branches.
* Recommended action: Ensure loose objects are secured or brought inside
The worst of the winds are likely in the afternoon. These winds may accompany a possible line of thundershowers when a front comes through tomorrow midday and/or may follow the front as the air dries out and higher pressure builds in.
Keep reading for information on why it's been so windy...
Unlike the last Saturday's wind event, the fire threat will be significantly lower due to the 0.5-1" of rain anticipated before and during the possible high wind. The air will dry rapidly behind the front tomorrow afternoon, but the vegetation/brush will have much higher water content.
So why has it been so windy?
In December and January, the wind was related to the weather patterns associated with the negative phase of the Arctic oscillation (AO). In that pattern, Arctic airmass after Arctic airmass originating from northern Canada dove southeast, driving windy cold fronts through the region. Low pressure often developed along these fronts over the ocean and difference between lows developing to our northeast and Arctic high pressure systems in their wake kept the wind going for days.
During the second half of February, even though the AO has gone into its positive or neutral phase, fast moving energetic weather systems along the northern jet stream - characteristic of both a La Nina pattern and the early spring season (often times March, when cold and warm air masses collide) - have generated less persistent but more intense winds - like we'll see tomorrow and saw last week.
The pattern into next week also seems to be conducive to short-lived high wind events, with some potential for another windy period next Monday.
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