The scale runs from F0 (40-72 m.p.h. on the low end) to F5 (261-318 m.p.h. on the high end), with F5 damage being described by Dr.Fujita as incredible. While never documented, an F6 tornado would ...

In the wake of yesterday’s massive tornado outbreak, the deadliest in almost 40 years ... Gummo and was believed by Fujita to be the closest to a recorded F6 tornado he’d seen evidence ...