What Are We Doing with (or to) the F-Scale?

Dr. T. Fujita developed the F-Scale to estimate hurricane and tornado intensity based on damage caused by their damage. The practical use of the scale was made evident by the thorough survey of damage from the 3 April 1974 Super Outbreak performed by Fujita and his staff at the University of Chicago. After they published their results, the F-Scale became the cornerstone of judging tornado character and strength. Tornado databases were updated to include the F-Scale based on past accounts and descriptions.

This presentation will discuss changes in the tornado database characteristics resulting from evolving applications of the F-scale guidelines. This is particularly relevant as the community embarks on the use of the new Enhanced Fujita Scale (EF-Scale). Topics will include how damage surveys from the 1970s into the middle 1990s effected the database; concerns about underrating or overrating damage, apparent establishment of comparison standards using previous tornadoes (e.g., how the 3 May 1999 Oklahoma tornado may now be the “F5 standard”), and how the latest training that incorporates evaluation of structural damage has influenced storm surveys and led to the development of the EF-Scale.