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Largest Tornado on Record and what it would look like in DFW

Today we learned from the NWS that the El Reno Tornado that struck on Friday, May 31, was the largest tornado on record with a width of 2.6 miles.  This breaks the previous largest tornado of 2.5 miles in Hallam, Nebraska, on May 22, 2004.  The largest tornado on record in Texas is debatable.  But the Edmonson, Texas, tornado on May 31, 1968, is likely one of the largest estimated at 2 miles.  This is between Amarillo and Lubbock in the Panhandle.



A 2.6 mile wide tornado would cover all of downtown Dallas.  From the AAC to Fair Park.

KTVT Street Level1

A 2.6 mile wide tornado would stretch from the Colonial Country Club to Downtown Fort Worth.

KTVT Street Level


The El Reno Tornado was also given a rating of EF-5 with winds around 295 mph.  In most cases, tornado intensity is estimated by looking at the damage caused by the tornado.  In the El Reno case, the damage from the tornado would only calculate out to an EF-3 rating.  But mobile doppler radar units were taking measurements of this tornado.

Here is a picture of one of those radars from the University of Oklahoma that measured a wind of 295 mph at 500 ft above the ground.


From this measurement, the National Weather Service went ahead and gave this tornado an EF-5 rating.  It is important to point out that even though the tornado was 2.6 miles wide, it was just a very small portion of that tornado where winds were measured around 295 mph .  The small little vortices that spun up within the broader circulation contained those higher winds.


This is the 2nd EF-5 Tornado in 11 days in Oklahoma.  The Moore, OK tornado on May 20, 2013, was also rated an EF-5 tornado.  In 108 years of record keeping, there have only been 14 F5/EF-5 Tornadoes in Oklahoma.



This is a question that many are asking.  I will theorize a few ideas.  First, this tornado that struck El Reno, 15 years ago would have been rated an EF-3 not an EF-5.  There was no physical damage on the ground to warrant an EF-5 rating.  But because of the data from the radar the rating is justified.

How many past tornadoes could have winds clocked at speeds warranting an EF-5 tornado?  Probably quite a few.  EF-5 Tornadoes are when winds are estimated to be above 200 mph.  Up until recently when radars were deployed to measure wind speed, the only way to estimate tornado wind speed was to look at the damage it caused.

Think of the countless tornadoes that did not affect anything or anyone.  The winds with these will never be known.  I think as we gather more data via mobile radar units, we might be surprised to find the intensity of the winds in localized areas within large tornadoes to be higher than first hypothesized.  The research will tell us more over the next few years.

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