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. 

How Does This Winter Rank ?

The end of meteorological winter has arrived.  The three month period of December, January and February comprise “meteorological winter.”  NOAA uses a running 30-year average (1980-2010) that’s updated every decade to determine what average temperatures and precipitation amounts are in Washington, D.C.

The 2017-2018 winter season could be divided into roughly two different halves with respect to temperature.  The period from December 1 through January 15 was exceptionally cold in the DC Metro Area.  That includes an 11-day stretch where temperatures remained at or below freezing on nine days (December 28, 2017 – January 7, 2018).  Despite the frigid temperatures, only 2.7” of snow occurred during this six-week period.  That speaks to the larger trend of dry weather from September 2017 through January 2018, when the Nation’s Capital had a rainfall deficit of more than nine inches.

Following DC’s driest January since 1981, moderate to severe drought conditions enveloped almost the entire DC Metro Area earlier this month.  Fortunately, a dramatic change in the weather pattern developed with measurable rainfall on 15 of the first 25 days of February.  Despite this, February 2018 has also been significantly warmer than average and that has meant below average snowfall. 

January 2018 had a mild second half with above average temperatures on 11 of the final 15 days.  That warmer than average trend continued into February, as this month is poised to finish as the third warmest on record in Washington, D.C.  In addition, the high temperature of 82° on February 21 was not only the earliest in the year 80° warmth occurred, but was also DC’s first 80° February day since February 28, 1948.

Despite this flip flop from cold and dry over the first half of the 2017-2018 winter season to warm and rainy for much of the second half, the lack of snowfall has persisted.  A total of only 3.3” of snow fell in Washington, D.C. this season or roughly 20% of the seasonal average of 15.4”.  

Washingtonians longing for snow shouldn’t give up hope altogether for seeing a little snowfall.  While last winter was also warmer and drier than average in the Nation’s Capital, March 2017 was snowier than average with two inches at National Airport.  Despite the expected cooler and wetter than average start to March 2018, NOAA says there is a 33% chance that it will feature warmer than average monthly temperatures in the Nation’s Capital and near average precipitation. 

Weather Quiz

True or False.

With 3.3” of snow the entire winter, the 2017-2018 winter is the third consecutive winter season with below average snowfall in Washington, D.C.

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Answer to February 14 Weather Quiz question.

B.  Norfolk, Virginia saw 13.1” of snow in January 2018 that is roughly four times the amount Washingtonians had the entire 2017-2018 winter season (3.3”).  In a rare set of circumstances, Atlanta (4.7”) and Birmingham (4.0”) also saw more snow than the Nation’s Capital this winter.

DC's warm and wet February

Not only was February 2017 DC’s warmest on record, it was also the sixth driest with only 0.68” of rain.  That’s roughly 25% of DC’s February average of 2.62”.  Similar to last year, this month will finish among the Top 5 warmest February’s.  However, unlike last year, February 2018 will rank among DC’s wettest.  That’s excellent news for DC area residents who have been experiencing very dry conditions over the prior several months.

Through February 25, Washington, D.C.’s average monthly temperature at National Airport is 44.8°.  Since February 10, all but three days have been warmer than average in the nation’s capital.  That includes seven days with temperatures of at least 65°, including the first 80° February temperature in the nation’s capital since 1948.

The nation’s capital had a rainfall deficit of more than 17” from August 2015 through January 2018.  During that time, DC had below average monthly precipitation in 24 out of 30 months.  In particular, from September 1, 2017 through January 31, 2018 when DC’s rainfall deficit was more than nine inches.  Consequently, much of the DC-Baltimore corridor was experiencing moderate to severe drought conditions earlier this month.

Fortunately, February 2018 has been exceptionally wet with measurable rainfall on 15 of the first 25 days of the month.  With 4.79” of rain as of February 25, this has already been DC’s wettest February since 2003.  As wet as this February has been, only 0.2” of snow occurred and that’s because it has been such a warm month in the nation’s capital.

This month’s wet spell has led to improvement in the drought conditions across the Mid-Atlantic Region.  Since the drought conditions occurred outside the growing season, they didn’t have the same impact that they could have.  Given the shift between the very dry month of February last year and the rainy February 2018 in the nation’s capital, it’s worth pointing out that DC’s hasn’t had consecutive wetter than average February’s since 1981-1986, according to NOAA.  Also, Washingtonians are experiencing their third consecutive warmer than average February for the first time since 1997-2002.

Top Ten Warmest February’s in Washington, D.C.  (Source: NOAA)

1.  47.7° (2017)

2.  46.9° (1976)

3.  45.2° (1990)

4.  44.7° (1997)

5.  44.4° (2012)

6.  43.8° (1984, 1949)

8.  43.7° (1981)
9.  43.5° (1954)

10.  43.4° (1998, 1890)

D.C.’s Top Ten Wettest February’s (Source: NOAA)

1.  6.98” (2003)
2.  6.84” (1884)
3.  6.47” (1897)

4.  6.17” (1899)
5.  5.71” (1961, 1939)
7.  5.62” (1979)
8.  5.44” (1971)
9.  5.32” (1903)
10.  5.31” (1896)

11.  5.27” (1972)
12.  5.26” (1900)
13.  5.23” (1996)
14.  5.09” (1882)
15.  5.08” (1883)
16.  4.72” (1902)