Dr. Ted (Tetsuya) Fujita created a tornado damage scale in 1970 after the Lubbock, Texas tornado. The damage scale was divided into six categories where F0 corresponded with minor damage to houses with estimated winds of 40 - 72 mph (18 – 32 m/s) all the way up to F5 where strong frame houses were swept off their foundations in estimated winds of 261 - 318 mph (117 – 142 m/s).
Dr. Fujita determined the failure wind speeds based on dividing the gap between the Beaufort Scale (which mariners use) and the Mach Scale (which aviators use) into 12 non-linear increments.
In the early 2000’s, wind engineering studies showed mounting evidence that wood-framed houses can be completely destroyed at wind speeds less than 261 mph (117 m/s).
Therefore, in 2001, the Wind Science and Engineering Center at Texas Tech University assembled a team of atmospheric scientists and wind engineers and developed the Enhanced Fujita (EF) Scale to address the inconsistencies of the F-Scale.