Severe Weather in the Nation’s Capital

 

Severe Reports for July 1, 2021 (Source: NOAA)

Although less common than in other parts of the country, severe weather also occurs in the Mid-Atlantic Region.  “Severe weather” refers to any of the following three criteria: 1) a thunderstorm with wind gusts of at least 58 mph; 2) hail 1”/+ in diameter or 3) tornado.  The strongest thunderstorms, known as “supercells,” have rotating updrafts and often feature more than one type of severe weather. 

Maryland and Virginia have each had several intense tornadoes.  The state of Maryland, for example, had two F4 tornadoes, including the Frostburg F4 that occurred in June 1998.  That was Maryland’s strongest until April 2002 when the town of La Plata in Charles County was devastated by an even strong F4 tornado.  Both would be ranked as EF-5 on the Enhanced Fujita Scale that went into operational use in 2007.  An F4 tornado also occurred in Petersburg, Virginia in August of 1993.

NOAA statistics indicate the state of Virginia averages 18 tornadoes and Maryland 10 in a given year.  Washington, D.C. itself doesn’t average any tornadoes given its relatively small geographic area.  That doesn’t mean the Nation’s Capital hasn’t seen its fair share of tornadic thunderstorms.  In fact, just last Thursday, July 1, two confirmed tornadoes occurred within D.C. City Limits.  An EF-0 with winds of approximately 80 mph occurred near the U.S. Capital.  A second tornado developed in Arlington and tracked across the Potomac into D.C.  It was an EF-1 with peak winds of 90 mph during its 4.4-mile path. 

Those were the first tornadoes in the District of Columbia since April 6, 2017.  Previously, the last time Washingtonians experienced a confirmed tornado was on September 24, 2001.  DC’s severe weather that day was overshadowed by the deadly F3 tornado that caused two fatalities in College Park, Maryland.

Washington, D.C. has been under tornado warnings many times in the last 20 years without any confirmed tornadoes, such as on June 1, 2012; October 15, 2014; and May 23, 2019.  Tornadoes don’t always occur when warnings are issued.  Severe thunderstorms frequently occur without confirmed tornadoes.

In addition to the tornadoes, what made last Thursday’s severe weather memorable in the D.C. Metro Area is that two rounds of severe weather occurred.  The first came during the peak heat of the afternoon and the second between 9:00 p.m. and 10:00 p.m. when the tornadoes developed.  That was the first time the Nation’s Capital had two waves of severe weather on the same day since June 4, 2008.