How Strong Do Tornadoes Get?

Where the Strongest Tornadoes have formed since 1950  (Source: SPC-NOAA)

The United States averages more tornadoes than any other country in the world due to its unique geography.  The strongest tornadoes form from large, long-lasting thunderstorms that rotate and are known as “supercells.”  Most supercells form during the spring when cold and dry air masses frequently collide with warm and humid air masses.  Landfalling tropical systems often spawn weaker tornadoes as well. 

Like Category 5 hurricanes, F5 and EF5 tornadoes are exceptionally rare.  Since 2000, there have been only nine F5/EF5 tornadoes in the United States.  The last EF5 tornado to occur in the U.S. was on May 20, 2013 (in Moore, Oklahoma).  It’s important to note that in 2007, the Fujita Tornado Intensity Scale was updated and is now known as the “Enhanced Fujita Scale” so tornadoes are ranked as an EF0 – EF5 instead of an F0 to an F5.  The original tornado intensity scale was designed by Dr. Ted Fujita of the University of Chicago.

On May 27, 1997, one of the most powerful tornadoes on record struck the town of Jarrell in central Texas.  Of the 20 tornadoes that formed 18 years ago today, the Jarrell, F5 was not only the strongest and most destructive, but was the deadliest with 27 fatalities.  This tornado was especially rough for farmers who lost approximately 300 cattle to the F5.  The Jarrell F5 was roughly ¾ of a mile in diameter and had a relatively long track of 7.6 miles.  It formed from an especially powerful supercell thunderstorm and was the last F5 to form in the state of Texas. 

Since 1950, there have been two days with multiple F5/EF5 tornadoes.  During what was dubbed the “Super Outbreak” on April 3, 1974, there were almost 150 tornadoes reported nationally.  Of those, seven were ranked an F5.  An even larger tornado outbreak occurred on April 27, 2011.  That’s when there were nearly 300 confirmed tornadoes with four ranked at EF5 intensity.  Although tornadoes occur more frequently in the United States than in any other country, an F5 or EF5 tornado are relative rare while days with multiple EF5’s are rarer still. 

There have been no observed F5/EF5 tornadoes in the Mid-Atlantic Region.  A relatively weak tornado (an F1) touched down in Olney, MD, on this date in 2001, but caused only minor damage.