Fujita Scale - Background

Background

The scale was introduced in 1971 by Tetsuya Fujita of the University of Chicago, in collaboration with Allen Pearson, head of the National Severe Storms Forecast Center (currently the Storm Prediction Center). The scale was updated in 1973, taking into account path length and width. In the United States, starting in 1973, tornadoes were rated soon after occurrence. The Fujita scale was applied retroactively to tornadoes reported between 1950 and 1972 in the National Oceanic and Atmospheric Administration (NOAA) National Tornado Database. Fujita rated tornadoes from 1916–1992 and Tom Grazulis of The Tornado Project retroactively rated all known significant tornadoes (F2-F5 or causing a fatality) in the U.S. back to 1880.

The Fujita scale was adopted in most areas outside of Great Britain.

In 2007, the Fujita scale was updated, and the Enhanced Fujita Scale was introduced in the United States. The new scale more accurately matches wind speeds to the severity of damage caused by the tornado.

Though each damage level is associated with a wind speed, the Fujita scale is effectively a damage scale, and the wind speeds associated with the damage listed aren't rigorously verified. The Enhanced Fujita Scale was formulated due to research which suggested that the wind speeds required to inflict damage by intense tornadoes on the Fujita scale are greatly overestimated. A process of expert elicitation with top engineers and meteorologists resulted in the EF scale wind speeds, however, these are biased to United States construction practices. The EF scale also improved damage parameter descriptions.