The Fujita scale, or Fujita–Pearson scale, is a scale for rating tornado intensity, based primarily on the damage tornadoes inflict on human-built structures and vegetation. The official Fujita scale category is determined by meteorologists and engineers after a ground or aerial damage survey, or both; and depending on the circumstances, ground-swirl patterns, weather radar data, witness testimonies, media reports and damage imagery, as well as photogrammetry or videogrammetry if motion picture recording is available. The Fujita scale was replaced with the Enhanced Fujita scale (EF-Scale) in the United States in February 2007. In April 2013, Canada adopted the EF-Scale over the Fujita scale along with 31 "Specific Damage Indicators" used by Environment Canada (EC) in their ratings.
Image: F0 tornado damage example
Image: F1 tornado damage example
Image: F2 tornado damage example
Image: F3 tornado damage example
Tornado intensity is the measure of wind speeds and potential risk produced by a tornado. Intensity can be measured by in situ or remote sensing measurements, but since these are impractical for wide-scale use, intensity is usually inferred by proxies, such as damage. The Fujita scale, Enhanced Fujita scale, and the International Fujita scale rate tornadoes by the damage caused. In contrast to other major storms such as hurricanes and typhoons, such classifications are only assigned retroactively. Wind speed alone is not enough to determine the intensity of a tornado. An EF0 tornado may damage trees and peel some shingles off roofs, while an EF5 tornado can rip well-anchored homes off their foundations, leaving them bare— even deforming large skyscrapers. The similar TORRO scale ranges from a T0 for extremely weak tornadoes to T11 for the most powerful known tornadoes. Doppler radar data, photogrammetry, and ground swirl patterns may also be analyzed to determine the intensity and assign a rating.
Tornado damage to a house in Oklahoma County, Oklahoma, hit during the Tornado outbreak of May 10–13, 2010
EF0 damage: This house only sustained a minor loss of shingles. Though well-built structures are typically unscathed by EF0 tornadoes, falling trees and tree branches can injure and kill people, even inside a sturdy structure. Between 35 and 40% of all annual tornadoes in the U.S. are rated EF0.
EF1 damage: Cause major damage to mobile homes and automobiles, and can cause minor structural damage to well-constructed homes. This frame home sustained major roof damage but otherwise remained intact. Around 35% of all annual tornadoes in the U.S. are rated EF1.
EF2 damage: At this intensity, tornadoes have a more significant impact on well-built structures, removing the roofs, and collapsing some exterior walls of poorly built structures. EF2 tornadoes are capable of destroying mobile homes and generating large amounts of flying debris. This home completely lost its roof, but its walls remained intact. Between 15 and 19% of all annual tornadoes in the U.S. are rated EF2.
