EF3

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 and France, among other countries. The EF scale is also unofficially used in other countries, including China and Brazil. 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 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. 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. 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 by the National Weather Service at a conference of the American Meteorological Society in Atlanta on February 2, 2006. 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 speeds and photographic damage examples have been updated, the damage descriptions given are based on those from the Fujita scale, which are more or less still accurate. However, for the actual EF scale in practice, damage indicators (the type of structure which has been damaged) are predominantly used in determining the tornado intensity.

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. The links in the right column of the following table describe the degrees of damage for the damage indicators listed in each row.

Differences from the Fujita scale

The Enhanced Fujita Scale takes into account the quality of construction and standardizes different kinds of structures. The wind speeds on the original scale were deemed by meteorologists and engineers as being too high, and engineering studies indicated that slower winds than initially estimated cause the respective degrees of damage. The old scale lists an F5 tornado as wind speeds of , while the new scale lists an EF5 as a tornado with winds above , found to be sufficient to cause the damage previously ascribed to the F5 range of wind speeds. None of the tornadoes in the United States recorded before February 1, 2007, were re-categorized during and after the transition to the EF Scale.

Essentially, there is no functional difference in how tornadoes are rated. The old ratings and new ratings are smoothly connected with a linear formula. The only differences are adjusted wind speeds, measurements of which were not used in previous ratings, and refined damage descriptions; this is to standardize ratings and to make it easier to rate tornadoes which strike few structures. Twenty-eight Damage Indicators (DI), with descriptions such as "double-wide mobile home" or "strip mall", are used along with Degrees of Damage (DoD) to determine wind estimates. Different structures, depending on their building materials and ability to survive high winds, have their own DIs and DoDs. Damage descriptors and wind speeds will also be readily updated as new information is learned. Some differences do exist between the two scales in the ratings assigned to damage. An EF5 rating on the new scale requires a higher standard of construction in houses than does an F5 rating on the old scale. So, the complete destruction and sweeping away of a typical American frame home, which would likely be rated F5 on the Fujita scale, would probably be rated EF4 or lower.

Since the EF Scale still uses actual tornado damage and similar degrees of damage for each category to estimate the storm's wind speed, the National Weather Service states that the scale will likely not lead to an increase in the number of tornadoes classified as EF5. Additionally, the upper bound of the wind speed range for EF5 is open—in other words, there is no maximum wind speed designated.

Rating classifications

For purposes such as tornado climatology studies, Enhanced Fujita scale ratings may be grouped into classes. Classifications are also used by NOAA's Storm Prediction Center to determine whether the tornado was "significant". This same classification is also used by the National Weather Service. The National Weather Service of Quad Cities uses a modified EF scale wording, which gives a new term for each rating on the scale, going from weak to catastrophic.

The table shows other variations of the tornado rating classifications based on certain areas.

See also

* Beaufort scale
* International Fujita scale
* Lists of tornadoes and tornado outbreaks
** List of F4, EF4, and IF4 tornadoes
** List of F5, EF5, and IF5 tornadoes
* Saffir–Simpson hurricane wind scale
* Severe weather terminology (United States)
* TORRO scale
* Tornado intensity and damage
* Wind engineering

References

*

External links

* National Oceanic and Atmospheric Administration
*
NOAA National Weather Service Improves Tornado Rating System
at NOAA News
*
The Enhanced Fujita Scale (EF Scale)
at Storm Prediction Center
*
EF-Scale Training
at The Warning Decision Training Branch of National Weather Service (NWS)
*
The Enhanced Fujita Tornado Scale
at National Climatic Data Center
*
The Tornado: An Engineering-Oriented Perspective
(NWS SR147)
*
A Guide for Conducting Convective Windstorm Surveys
(NWS SR146)

Fujita Scale Enhancement Project
( Wind Science and Engineering Research Center at Texas Tech University)

Symposium on the F-Scale and Severe-Weather Damage Assessment
at American Meteorological Society

A Guide to F-Scale Damage Assessment
MetEd, University Corporation for Atmospheric Research

Mitigation Assessment Team Report: Midwest Tornadoes of May 3, 1999
(Federal Emergency Management Agency)

{{Tornado navbox
Hazard scales
Wind
Tornado
Scales in meteorology