Texas Tech University

Enhanced Fujita Scale

 Dr. Ted Fujita (1971) developed the Fujita Scale to provide a method to rate the intensity of tornadoes. The intent of the scale was to distinguish between weak tornadoes and strong tornadoes. There was a need to be able to rate tornadoes in the historical database as well as future tornadoes as they occur. The meteorological and engineering communities almost immediately accepted the Fujita Scale.

The National Weather Service (NWS) applies the Fujita Scale in rating tornadoes as they occur. Dr. Fujita's group at the University of Chicago and personnel at the National Severe Storms Forecast Center (NSSFC) ndependently assigned Fujita Scale ratings to tornadoes in the historical records based on written descriptions of the damage. The University of Chicago database has not been kept up to date in recent years. The Storm Prediction Center (SPC) maintained the NSSFC database through 1995. Tornado records since that time are kept at the National Climatic Data Center in Asheville, NC.

Although the Fujita Scale has been in use for 33 years, the limitations of the scale are well known to the users. The primary limitations are a lack of damage indicators, no account of construction quality and variability and no definitive correlation between damage and wind speed. These limitations have led to inconsistent rating of tornadoes and in some cases an overestimate of tornado wind speeds. Thus, there is a need to revisit the concept of the Fujita Scale and to improve and eliminate some of the limitations. The Enhanced Fujita Scale proposed is referred to as the EF Scale to distinguish it from the original Fujita Scale. 

F Number Fastest 1/4-mile(mph) 3 Second Gust (mph) EF Number 3 Second Gust (mph) EF Number 3 Second Gust (mph)
0 40-72 45-78 0 65-85 0 65-85
1 73-112 79-117 1 86-109 1 86-110
2 113-157 118-161 2 110-137 2 111-135
3 158-207 162-209 3 138-167 3 136-165
4 208-260 210-261 4 168-199 4 166-200
5 261-318 262-317 5 200-234 5 Over 200