How Rare are EF-5 and F5 Tornadoes?

59 F5 / EF5 Tornadoes Have Occurred since 1950  (Source: NOAA)

Tornado intensity is ranked on the Enhanced Fujita Scale.  Created by the late-Dr. Ted Fujita of the University of Chicago, the original Fujita Scale was introduced in 1971.  The weakest tornadoes are the most common with an F0 having winds of 40-72 mph, capable of “light damage.”  The strongest and rarest tornadoes were ranked as an F5 that were capable of “incredible” damage with winds of 261 mph or greater.  In 2007, the “Fujita Scale” was updated and has since been known operationally as the “Enhanced Fujita Scale.”

On the updated scale, the weakest tornado, an EF-0, has wind speeds of 65-85 mph while the strongest tornadoes, EF-5’s, have wind speeds of greater than 200 mph.  That’s a significant difference since Maryland’s strongest observed tornado was an F4 that developed in April 2002.  However, on the “Enhanced” Fujita scale, the same tornado that devastated La Plata in 2002 would have been ranked an EF-5.

One of the largest severe weather outbreaks in U.S. History occurred during the early days of the Fujita Scale on April 3-4, 1974.  Known as the “Super Outbreak,” NOAA confirmed a total 148 tornadoes that developed in 13 states.  This outbreak was historic for the high percentage of “violent” tornadoes with 30 of the 148 tornadoes that developed classified as F4 or greater with winds of at least 207 mph.  That includes seven F5 tornadoes and that remains the highest such number to occur during any U.S. severe weather outbreak. 

According to NOAA there have been only 59 F5 or EF-5 tornadoes across the United States since 1950. Such intense tornadoes only form under the rarest of circumstances (similar to Category 5 hurricanes). Another significant tornado outbreak occurred on April 27, 2011 when four EF-5 tornadoes developed.  As the population has increased and technology has improved, tornado detection has increased as has the ability to provide advance warning.

Since 1997, there has been a combined total of 13 F5/EF-5 tornadoes in the United States.  Texas residents will soon mark the 20^th anniversary of the Jarrell F5 that occurred on May 27, 1997.  Although no F5/EF-5 tornado occurred in the United States from 1999 to 2007, a total of six EF-5 tornadoes occurred in 2011.  The states of Oklahoma and Alabama are tied with the most F5/EF-5 tornadoes (7).  By comparison, the two tornadoes that developed in Washington, D.C. on April 6, 2017 were each ranked an EF-0.