Notable May Severe Weather Events

 

U.S. Tornado Averages  (Source: NOAA)

May is one of the most active severe weather months of the year in the United States.  “Severe weather” is defined as a thunderstorm that produces any of the following: A) wind gusts of at least 58 mph; B) hail 1” in diameter or greater; or C) a tornado.  The most dangerous thunderstorms (supercells) can have more than one type of severe weather as large hail often precedes tornadoes.  Locally, the D.C. Metro Area has had a number of memorable May severe weather events.   

2019:  Three tornadoes touched down in central Maryland on May 30 with two EF-0’s and an EF-1 in Frederick and Howard Counties.  Wind damage was more widespread across the D.C. Metro Area with a wind gust as high as 66 mph reported at Davison Army Airfield in Fairfax County, Virginia. 

Just a week earlier more severe weather impacted the D.C. Metro Area.  An EF-1 tornado was confirmed in Columbia, Maryland that caused some structural damage.  There were also multiple severe wind gusts from the thunderstorms that developed.  Winds gusted as high as 66 mph at National Airport, 63 mph at Andrews AFB in Maryland, and 67 mph in Gaithersburg, Maryland.  Damage reports on May 23 ranged from downed trees and power lines to minor structural damage of homes and businesses.

2013:  The last EF-5 tornado in the United States occurred on May 20 in Moore, Oklahoma.  It had a long and destructive track as part of a larger, three-day severe weather outbreak.  The strongest tornadoes often develop from something called a “supercell thunderstorm,” which is a long-lasting thunderstorm that has a rotating updraft.

One of the supercell thunderstorms during this outbreak spawned the Moore, OK tornado.  Although not at EF-5 intensity during its entire track, it reached its peak intensity near the town of Moore with winds of greater than 200 mph.  According to NOAA, it remains the third costliest tornado on record having caused $2 billion in damage (unadjusted for inflation). 

2011:  A deadly EF-5 tornado devastated the town of Joplin, Missouri on May 22.  According to the National Weather Service, it was one of the deadliest in U.S. history with 122 fatalities and more than 700 injured.  NOAA also ranks the Joplin tornado as the most destructive on record in the United States, having caused an estimated $2.8 billion in damages (unadjusted for inflation).

The spring of 2011 was an unusually active severe weather season for the United States with a total of six EF-5 tornadoes.  That was the highest annual total since 1974.

2007: The town of Greensburg, Kansas, was impacted by an EF-5 tornado on May 4 that was both destructive and deadly.  It was also significant for being the first tornado to be ranked an “EF-5” since the updated or “Enhanced” Fujita Scale went into operational use earlier that year.  This tornado is widely considered to be the strongest U.S. tornado since 1999.

1999:  The last observed F5 tornado in the United States occurred on May 3 before the Fujita Scale was updated or “enhanced” in 2007.  The town of Moore, Oklahoma also saw impacts from this devastating tornado that at the time was the third costliest tornado in the United States.  However, the $1 billion in damage it caused (roughly $1.4 billion in 2015 dollars) makes it “only” the sixth costliest tornado in U.S. history today.