EFscale

The Enhanced Fujita scale, or EF-scale, is a system used to rate the intensity of tornadoes based on the damage they cause. It is applied in post-storm surveys in the United States and Canada and provides estimated wind speeds tied to observed destruction rather than direct measurements. The EF-scale was introduced in 2007 as an update to the original Fujita scale, with the goal of improving consistency across different building types and construction practices.

Historically, the original Fujita scale was developed by Ted Fujita in 1971 and rated tornadoes from F0 to F5. The Enhanced Fujita scale was created to address limitations of the F-scale by incorporating a larger set of Damage Indicators and Degrees of Damage, enabling more accurate wind estimates across diverse structures. Official ratings are assigned by meteorologists after on-site damage surveys.

The EF-scale comprises 28 Damage Indicators covering various structure types and objects, each evaluated for degrees of damage. The combined assessment yields a rating from EF0 to EF5, with approximate wind speed ranges: EF0 65–85 mph, EF1 86–110 mph, EF2 111–135 mph, EF3 136–165 mph, EF4 166–200 mph, and EF5 greater than 200 mph.

Limitations include the reliance on observed damage rather than direct wind measurements, which means wind speeds are estimates that can be affected by construction quality, debris patterns, and land use. Surveys may be incomplete in some areas, and ratings can be revised as new information becomes available. Despite these caveats, the EF-scale provides a standardized framework for communicating tornado severity and informing hazard assessment, risk management, and public safety efforts in North America.