Enhanced Fujita scale

The Enhanced Fujita Scale or EF Scale, which became operational on February 1, 2007, is used to assign a tornado a 'rating' based on estimated wind speeds and related damage in some countries, including the United States and Canada. When tornado-related damage is surveyed, it is compared to a list of Damage Indicators (DIs) which help better estimate the range of wind speeds the tornado likely produced. From that, a rating (from EF0 to EF5) is assigned.

The EF Scale was revised from the original Fujita scale to reflect better examinations of tornado damage surveys so as to align wind speeds more closely with associated storm damage. The new scale has to do with how most structures are designed.

Estimated wind values for each tornado category: