NASHVILLE, Tenn. (WKRN) — Droughts are typically not good news, but a drought in the most violent and destructive of tornadoes is a good thing.
A new record drought of EF-5 tornadoes is anticipated for this week.
The last EF-5 tornado to hit the U.S. was on May 20, 2013, in Moore, Oklahoma. That tornado flattened homes and other structures, killing 24 people. While there have been violent tornadoes since then, none have been rated an EF-5.
Harold Brooks, PhD, Senior Research Scientist at the National Severe Storms Laboratory said it’s hard to tell if there is a meteorological reason for the lack of EF-5’s or if it is related to how tornadoes are rated.
“It’s kind of hard to tell when you’ve already got a rare event to start with. And, if you make even the smallest changes in how the reporting is done, then it can affect how we look at things. That said, we can’t tell if this is what we call meteorologically real. Or if it is, how much of it is an artifact of the reporting changes.”
The Enhanced Fujita Scale, which is used to rate tornadoes, estimates wind based on the damage that occurs to structures. If a tornado hits in an area that doesn’t have many sturdy structures, then it’s hard to rate. A good example of this is the massive tornado that hit El Reno, Oklahoma just 11 days after the Moore Oklahoma EF-5.
“Certainly the El Reno radar observations are well above the minimum wind speed for any EF-5. But, it also didn’t hit very much. The structures that were it were few and far between,” said Dr. Brooks. The El Reno tornado was officially rated as an EF-3.
Even when there isn’t an “EF-5 Drought”, EF-5 tornadoes are incredibly rare in Middle Tennessee. The only one to hit Middle Tennessee was on April 16, 1998, also known as the “Forgotten F-5.”