The Enhanced Fujita scale (abbreviated EF-Scale) is a scale that rates tornado intensity based on the severity of the damage a tornado causes. It is used in the United States, Brazil and France, among other countries. The EF scale is also unofficially used in other countries, including China. The rating of a tornado is determined by conducting a tornado damage survey.
The scale has the same basic design as the original Fujita scale—six intensity categories from zero to five, representing increasing degrees of damage. It was revised to reflect better examinations of tornado damage surveys, in order to align wind speeds more closely with associated storm damage. Better standardizing and elucidating what was previously subjective and ambiguous, it also adds more types of structures and vegetation, expands degrees of damage, and better accounts for variables such as differences in construction quality. An "EF-Unknown" (EFU) category was later added for tornadoes that cannot be rated due to a lack of damage evidence.
As with the Fujita scale, the Enhanced Fujita scale is a damage scale and only an estimate for actual wind speeds. While the wind speeds associated with the damage listed did not and have not undergone empirical analysis (such as detailed physical or any numerical modeling) due to expensive costs, the wind speeds were obtained through a process called expert elicitation, which was based on various engineering studies since the 1970s as well as from the field experience of meteorologists and engineers. Unlike the original Fujita scale and International Fujita scale, ratings on the Enhanced Fujita scale are based solely off the effects of 3-second gusts on any given damage indicator.
History The Enhanced Fujita scale replaced the decommissioned Fujita scale that was introduced in 1971 by Ted Fujita.Fujita, T. Theodore (February 1971) "Proposed characterization of tornadoes and hurricanes by area and intensity". SMRP (Satellite and Mesometeorology Research Project) Research Paper 91 (Department of the Geophysical Sciences, University of Chicago, Chicago, Illinois, USA) 42 pages. Operational use began in the United States on February 1, 2007, followed by Canada on April 1, 2013, who uses a modified version known as the CEF-scale. It has also been in use in France since 2008, albeit modified slightly by using damage indicators that take into account French construction standards, native vegetation, and the use of metric units. In Brazil, the EF Scale is used by the Reporting Platform and Voluntary Network of Severe Storm Observers (PREVOTS) since June 2018, and by other agencies since 2025. Similarly, the Japanese implementation of the scale is also modified along similar lines; the Japanese variant is referred to locally in Japan as the JEF or Japanese Enhanced Fujita Scale. The scale is also used unofficially in other countries, such as China.
The newer scale was publicly unveiled on October 4, 2004, at the American Meteorological Society's 22nd Conference on Severe Local Storms in Hyannis, Massachusetts. It was developed from 2000 to 2004 by the Fujita Scale Enhancement Project of the Wind Science and Engineering Research Center at Texas Tech University, which brought together dozens of expert meteorologists and civil engineers in addition to its own resources.
The scale was used for the first time in the United States a year after its public announcement when parts of central Florida were struck by multiple tornadoes, the strongest of which were rated at EF3 on the new scale.
In November 2022, a research paper was published that revealed a more standardized EF-scale was in the works. This newer scale is expected to combine and create damage indicators, and introduce new methods of estimating wind speeds in tornadoes. Some of these newer methods include mobile doppler radar and forensic engineering.
In 2024, Anthony W. Lyza, Matthew D. Flournoy, and A. Addison Alford, researchers with the National Severe Storms Laboratory, Storm Prediction Center, CIWRO, and the University of Oklahoma's School of Meteorology, published a paper stating, ">20% of supercell tornadoes may be capable of producing EF4–EF5 damage".
Parameters The seven categories for the EF scale are listed below, in order of increasing intensity. Although the wind speed estimates and photographic damage examples have been updated, the damage descriptions are broadly derived from those used with the Fujita scale. In operational practice, however, damage indicators and degrees of damage are predominantly used in determining tornado intensity. +ScaleFrequencyDescriptorExample of damagemphkm/hknotsEFU3.11%No surveyable damage rowspan="2" Intensity cannot be determined due to a lack of information. This rating applies to tornadoes that traverse areas with no damage indicators, cause damage in an area that cannot be accessed by a survey, or cause damage that cannot be differentiated from that of another tornado.EF065–85105–13757–7452.82%Light damageWell-built structures are typically unscathed, sometimes sustaining broken windows, with minor damage to roofs and chimneys. Billboards and large signs can be knocked down. Trees may have large branches broken off and may be uprooted if they have shallow roots.EF186–110138–17775–9532.98%Moderate damageDamage to mobile homes and other temporary structures becomes significant, and cars and other vehicles may be pushed off the road or flipped. Permanent structures can suffer major damage to their roofs, with corners or edges of roofs being torn off completely. Larger trees can be uprooted.EF2111–135178–21796–1178.41%Considerable damageWell-built structures can suffer severe damage (including roof loss), and the collapse of some exterior walls may occur in poorly built structures. Mobile homes are often heavily damaged or destroyed. Vehicles can be lifted off the ground, and lighter objects can become small missiles, causing damage outside of the tornado's main path. Wooded areas have a large percentage of their trees snapped or uprooted.EF3136–165218–266118–1432.18%Severe damageA few parts of affected buildings are left standing. Well-built structures lose all outer and some inner walls. Unanchored homes are swept away, and homes with poor anchoring may collapse entirely. Trains and train cars are all overturned. Small vehicles and similarly sized objects are lifted off the ground and tossed as projectiles. Wooded areas suffer an almost total loss of vegetation and some tree debarking may occur.EF4166–200267–322144–1740.45%Devastating damageWell-built homes are reduced to a short pile of medium-sized debris on the foundation. Homes with poor or no anchoring are swept completely away. Large, heavy vehicles, including airplanes, trains, and large trucks, can be pushed over, flipped repeatedly, or picked up and thrown. Large, healthy trees are entirely debarked and snapped off close to the ground or uprooted altogether and turned into flying projectiles. Passenger cars and similarly sized objects can be picked up and flung for considerable distances. EF5201+323+175+0.05%Incredible damageWell-built and well-anchored homes are swept cleanly off their foundations and obliterated. Large, steel-reinforced structures such as schools are completely leveled. Low-lying grass and vegetation are shredded from the ground. Trees are completely debarked and snapped. Very little recognizable structural debris is generated with most materials reduced to a coarse, dispersed mix of small, granular particles. Large, multiple-ton steel frame vehicles and farm equipment are often mangled beyond recognition and tossed miles away or reduced entirely to unrecognizable parts. Tall buildings collapse or suffer severe structural deformation.
Damage indicators and degrees of damage The EF scale currently has 28 damage indicators (DI), or types of structures and vegetation, each with a varying number of degrees of damage (DoD). Each structure has a maximum DoD value, which is given by total destruction. Lesser damage to a structure will yield lower DoD values. Wind speed estimates are divided into three categories; Lower Bound (LB), Expected (EXP), and Upper Bound (UB). EXP is the average wind speed estimate needed to cause the DoD for the "typical construction" of the DI. If the construction of the DI was better/worse than typical, the LB/UB values would be used.