Enhanced Fujita Scale

Enhanced Fujita Scale

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The Enhanced Fujita Scale (EF Scale) rates the strength of tornado
Tornado
A tornado is a violent, dangerous, rotating column of air that is in contact with both the surface of the earth and a cumulonimbus cloud or, in rare cases, the base of a cumulus cloud. They are often referred to as a twister or a cyclone, although the word cyclone is used in meteorology in a wider...

es in the United States
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...

 based on the damage they cause.

Implemented in place of the Fujita scale
Fujita scale
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...

 introduced in 1971 by Ted Fujita
Ted Fujita
was a prominent severe storms researcher. His research at the University of Chicago on severe thunderstorms, tornadoes, hurricanes and typhoons revolutionized knowledge of each.- Biography :Fujita was born in Kitakyūshū, Fukuoka Prefecture, Japan...

, it began operational use on February 1, 2007. The scale has the same basic design as the original Fujita scale: six categories from zero to five representing increasing degrees of damage. It was revised to reflect better examinations of tornado damage surveys, so as 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, vegetation, expands degrees of damage, and better accounts for variables such as differences in construction quality.

The new scale was publicly unveiled by the National Weather Service
National Weather Service
The National Weather Service , once known as the Weather Bureau, is one of the six scientific agencies that make up the National Oceanic and Atmospheric Administration of the United States government...

 at a conference of the American Meteorological Society
American Meteorological Society
The American Meteorological Society promotes the development and dissemination of information and education on the atmospheric and related oceanic and hydrologic sciences and the advancement of their professional applications. Founded in 1919, the American Meteorological Society has a membership...

 in Atlanta
Atlanta, Georgia
Atlanta is the capital and most populous city in the U.S. state of Georgia. According to the 2010 census, Atlanta's population is 420,003. Atlanta is the cultural and economic center of the Atlanta metropolitan area, which is home to 5,268,860 people and is the ninth largest metropolitan area in...

 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
Wind Science and Engineering Research Center
The Wind Science and Engineering Research Center at Texas Tech University is an interdisciplinary research center focused on education and information outreach. Its goals are to exploit the useful qualities of wind and to mitigate its detrimental effects...

 at Texas Tech University
Texas Tech University
Texas Tech University, often referred to as Texas Tech or TTU, is a public research university in Lubbock, Texas, United States. Established on February 10, 1923, and originally known as Texas Technological College, it is the leading institution of the Texas Tech University System and has the...

, which brought together dozens of expert meteorologists and civil engineer
Civil engineer
A civil engineer is a person who practices civil engineering; the application of planning, designing, constructing, maintaining, and operating infrastructures while protecting the public and environmental health, as well as improving existing infrastructures that have been neglected.Originally, a...

s in addition to its own resources.

As with the Fujita scale, the Enhanced Fujita Scale remains a damage scale and only a proxy for actual wind speeds. While the wind speeds associated with the damage listed have not undergone empirical analysis (e.g., detailed physical or any numerical modelling) owing to excessive cost, the wind speeds were obtained through a process of expert elicitation
Expert elicitation
In science, engineering, and research, expert elicitation is the synthesis of opinions of experts of a subject where there is uncertainty due to insufficient data or when such data is unattainable because of physical constraints or lack of resources. Expert elicitation is essentially a scientific...

 based on various engineering studies since the 1970s as well as from field experience of meteorologists and engineers. In addition to damage to structures and vegetation, radar data, photogrammetry
Photogrammetry
Photogrammetry is the practice of determining the geometric properties of objects from photographic images. Photogrammetry is as old as modern photography and can be dated to the mid-nineteenth century....

, and cycloidal marks (ground swirl patterns) may be utilized when available.

The scale was used for the first time a year after its public announcement when parts of central Florida were struck by multiple tornadoes
2007 Central Florida tornadoes
The 2007 Groundhog Day tornado outbreak was a localized but devastating tornado event that took place in central Florida early on February 2, 2007. Early morning temperatures had risen well above average for the season; combined with increased moisture and a powerful jet stream, this created enough...

, the strongest of which were rated at EF3 on the new scale. The first time the EF5 assessment was used was the Greensburg, Kansas tornado
May 2007 Tornado Outbreak
The May 2007 Tornado Outbreak was an extended tornado outbreak that started on May 4, 2007, affecting portions of the Central United States. The most destructive tornado in the outbreak occurred on the evening of May 4 in western Kansas, where about 95% of the city of Greensburg in Kiowa County was...

 that occurred on May 4, 2007.

Parameters


The six categories for the EF Scale are listed below, in order of increasing intensity. Although the wind speeds and photographic damage examples are updated, the damage descriptions given are 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 predominately used in determining the tornado intensity.
Scale Wind speed
(Estimated)
Example of damage
mph km/h
EF0 65–85 105–137
EF1 86–110 138–178
EF2 111–135 179–218
EF3 136–165 219–266
EF4 166–200 267–322
EF5 >200 >322

Damage indicators and degrees of damage


The EF Scale currently has 28 damage indicators (DI), or types of structures and vegetation, with a varying number of degrees of damage (DoD) for each.
DI No. Damage Indicator (DI) Degrees of Damage (DOD)
1 Small Barns or Farm Outbuildings (SBO) 8
2 One- or Two-Family Residences (FR12) 10
3 Manufactured Home – Single Wide (MHSW) 9
4 Manufactured Home – Double Wide (MHDW) 12
5 Apartments, Condos, Townhouses [3 stories or less] (ACT) 6
6 Motel (M) 10
7 Masonry Apartment or Motel Building (MAM) 7
8 Small Retail Building [Fast Food Restaurants] (SRB) 8
9 Small Professional Building [Doctor’s Office, Branch Banks] (SPB) 9
10 Strip Mall (SM) 9
11 Large Shopping Mall (LSM) 9
12 Large, Isolated Retail Building [K-Mart, Wal-Mart] (LIRB) 7
13 Automobile Showroom (ASR) 8
14 Automobile Service Building (ASB) 8
15 Elementary School [Single Story; Interior or Exterior Hallways] (ES) 10
16 Junior or Senior High School (JHSH) 11
17 Low-Rise Building [1–4 Stories] (LRB) 7
18 Mid-Rise Building [5–20 Stories] (MRB) 10
19 High-Rise Building [More than 20 Stories] (HRB) 10
20 Institutional Building [Hospital, Government or University Building] (IB) 11
21 Metal Building System (MBS) 8
22 Service Station Canopy (SSC) 6
23 Warehouse Building [Tilt-up Walls or Heavy-Timber Construction] (WHB) 7
24 Electrical Transmission Lines (ETL) 6
25 Free-Standing Towers (FST) 3
26 Free-Standing Light Poles, Luminary Poles, Flag Poles (FSP) 3
27 Trees: Hardwood (TH) 5
28 Trees: Softwood (TS) 5

Differences from the Fujita scale


The new scale takes into account 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 261-318 mph (419-512 km/hr), while the new scale lists an EF5 as a tornado with winds above 200 mph (324 km/h), found to be sufficient to cause the damage previously ascribed to the F5 range of wind speeds. None of the tornadoes recorded on or before January 31, 2007 will be re-categorized.

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; 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
Mobile home
Mobile homes or static caravans are prefabricated homes built in factories, rather than on site, and then taken to the place where they will be occupied...

" or "Strip mall
Strip mall
A strip mall is an open-area shopping center where the stores are arranged in a row, with a sidewalk in front. Strip malls are typically developed as a unit and have large parking lots in front...

", 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.

Since the new system 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 new scale will likely not lead to an increase in a 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

Tornado rating classifications
EF0 EF1 EF2 EF3 EF4 EF5
Weak Strong Violent
Significant
Intense

For purposes such as tornado climatology
Tornado climatology
The United States has the most tornadoes of any country, nearly four times more than estimated in all of Europe, excluding waterspouts. This is mostly due to the unique geography of the continent. North America is a large continent that extends from the tropics north into arctic areas, and has no...

 studies, Enhanced Fujita scale ratings may be grouped into classes.

See also

  • Fujita scale
    Fujita scale
    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...

  • TORRO scale
    TORRO scale
    The TORRO tornado intensity scale is a scale measuring tornado intensity between T0 and T11. It was developed by Terence Meaden of the Tornado and Storm Research Organisation , a meteorological organisation in the United Kingdom, as an extension of the Beaufort scale.- History and derivation from...

  • Beaufort scale
    Beaufort scale
    The Beaufort Scale is an empirical measure that relates wind speed to observed conditions at sea or on land. Its full name is the Beaufort Wind Force Scale.-History:...

  • Saffir-Simpson Hurricane Scale
    Saffir-Simpson Hurricane Scale
    The Saffir–Simpson Hurricane Scale , or the Saffir–Simpson Hurricane Wind Scale , classifies hurricanes — Western Hemisphere tropical cyclones that exceed the intensities of tropical depressions and tropical storms — into five categories distinguished by the intensities of their sustained winds...

  • Tornado intensity and damage
    Tornado intensity and damage
    The Fujita scale and the Enhanced Fujita Scale rate tornadoes by damage caused. The Enhanced Fujita Scale was an upgrade to the older Fujita scale, with engineered wind estimates and better damage descriptions, but was designed so that a tornado rated on the Fujita scale would receive the same...

  • List of tornadoes and tornado outbreaks
  • List of F5 and EF5 tornadoes
  • Severe weather terminology
    Severe weather terminology (United States)
    This article describes the United States National Weather Service severe weather terminology. The NWS defines precise meanings for nearly all its weather terms. This article describes NWS terminology and related NWS weather scales...


External links