March Came in like a Lion

March 2018 has certainly entered like a lion across the eastern United States.  A powerful Nor’Easter brought the Mid-Atlantic Region a prolonged period of damaging winds.  Friday’s high wind event – with several gusts above 70 mph in the DC Metro Area – caused considerable damage and widespread power outages.  Virtually all school districts and the Federal Government were closed on March 2 as a precaution.

Winds are the result of differences between areas of high and low pressure.  The smaller the physical distance between areas of high and low pressure (known as a “gradient”), the higher the wind speeds tend to be.  What made Friday’s school closures especially noteworthy was the fact no accumulating snow occurred in the DC Metro Area with this storm.  The closures were caused exclusively by the high winds and ancillary power outages.  In turn, the power outages and downed trees caused delays and cancellations to road, rail and air traffic.

Some of Friday’s highest wind gusts (mph) in the DC Metro Area include:

Dahlgren, Va. – 75
Dulles Airport, Sterling, VA. – 71
Gaithersburg, Md. – 69
National Airport (DCA), Virginia – 62
BWI Airport, Baltimore, MD – 61

These wind gusts were similar to the June 29, 2012 derecho in the Nation’s Capital.  During the derecho, Dulles also had a wind gusts to 71 mph, while National’s peak wind gust was 70 mph and BWI’s was 66 mph.  They were all strong tropical storm force wind gusts and also met the criteria for a severe thunderstorm.  Yesterday’s wind gust in Dahlgren, VA, of 75 mph was equivalent to a minimal, Category 1 hurricane.  

There are differences between the June 2012 derecho and yesterday’s wind event.  The derecho was a very short-lived event that lasted a matter of minutes, while yesterday’s high winds lasted the entire day.  The other major difference is the time of year.  In late June the trees have a full canopy of leaves which make them susceptible to high winds.  Without any leaves yesterday, the trees were much lighter than they otherwise would be.  The first six months of 2012 all featured below average rainfall in the Nation’s Capital and June 2012 had also been a very hot month.  This combination created hard and dry ground conditions.  By comparison, after a very wet February the soil was much softer and it was easier for larger trees to be uprooted in yesterday’s high winds.

March is typically a very windy month in the Nation’s Capital.  It is the first month of “meteorological spring” that runs through the end of May.  Washingtonians can expect a high degree of weather variability during March.  For example, March 2012 was DC’s warmest on record, while March 2014 was DC’s snowiest March since 1960.  Meanwhile, last March was the snowiest month of the entire year.