MOORE, Okla. – It has been nine years since a catastrophic EF-5 tornado was last documented in the United States. It has also been the longest span between "5-rated" twisters in historical records dating to 1950.
The nation's last EF-5 tornado struck Moore, Oklahoma, on May 20, 2013.
The previous record spanned nearly eight years to the day, between the F-5 twister that tore through Moore and Oklahoma City, Oklahoma, on May 3, 1999, and the EF-5 tornado that nearly wiped out the entire town of Greensburg, Kansas, on May 4, 2007. (The original Fujita Scale was updated to the Enhanced Fujita Scale and implemented in the United States on Feb. 1, 2007.)
EF-5 tornadoes are among the rarest cyclones on the planet. In the U.S., there have been only 59 EF-5 twisters since 1950, according to NOAA's Storm Prediction Center. That works out to an average of less than one EF-5 tornado in America each year. However, some years have reported multiple tornadoes of this intensity, while there have also been multi-year stretches without a single 5-rated twister such as the current nine-year streak.
An EF-5/F-5 tornado has been documented in 19 states, ranging from as far north as Fargo, North Dakota, to as far south as Central Texas and as far east as Ohio near its border with Pennsylvania.
Alabama and Oklahoma have recorded the greatest number of tornadoes with a rating of 5 on the Fujita/Enhanced Fujita Scale, each with seven such twisters since 1950. Iowa, Kansas and Texas have each seen six EF-5/F-5 tornadoes.
Leading the way with the most EF-5/F-5 tornadoes in a single year is 1974 when seven such twisters were reported during the Super Outbreak of April 3. Among that day's 5-rated tornadoes, three struck Alabama, two hit Ohio, and Indiana and Kentucky each saw one.
Just over 37 years later, six EF-5/F-5 twisters touched down in the spring of 2011. Four occurred during the April 27 Super Outbreak in Alabama and Mississippi, each reporting two EF-5 tornadoes that day. The year's other two EF-5s struck Joplin, Missouri, and El Reno/Piedmont, Oklahoma, on May 22 and 24, respectively.
Any twister can turn deadly if people in its way are caught unprepared. However, those rated a 4 or a 5 on the Fujita/Enhanced Fujita Scale have historically killed the greatest number of people. In fact, 50.48% of all tornado deaths over the 20-year period from 2000 through 2019 were caused by EF-4 or EF-5 twisters, according to data from the SPC. The remaining 49.52% of the deaths were from tornadoes rated EF-0 to EF-3.
All 15 tornadoes in U.S. history that were blamed for 100 or more deaths received a rating of EF-4/F-4 or EF-5/F-5, according to the SPC.
How does a tornado receive an EF-5 rating?
A tornado is assigned a rating from 0 to 5 on the Enhanced Fujita Scale to estimate its intensity in terms of damage and destruction caused along the twister’s path.
Meteorologists from the National Weather Service conduct storm surveys in the days following suspected tornadoes and estimate wind speeds based on the damage they observe while out in the field, using the criteria from the Enhanced Fujita Scale for guidance.
Measuring actual wind speeds inside twisters is a difficult feat because any weather instruments placed in their path are likely to be destroyed.
In order for a tornado to receive an EF-5 rating, the NWS says the damage must be catastrophic. Winds in an EF-5 twister are greater than 200 mph.
EF-5 tornadoes will destroy well-built frame houses and sweep their foundations clean of debris. In addition, steel-reinforced concrete structures will be critically damaged, and tall buildings will collapse or have severe structural deformations. Cars, trucks and trains can even be tossed to about 1 mile away.