Enhanced Fujita scale

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Enhanced Fujita Scale
EF0EF1EF2EF3EF4EF5

The Enhanced Fujita Scale (EF scale) rates the strength of tornadoes in the United States and Canada based on the damage they cause.

Implemented in place of the Fujita scale introduced in 1971 by Tetsuya Theodore Fujita, it began operational use in the United States on February 1, 2007, followed by Canada on April 1, 2013.[1][2] 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 and 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 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.

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 (such as detailed physical or any numerical modelling) owing to excessive cost, the wind speeds were obtained through a process of expert elicitation 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, and cycloidal marks (ground swirl patterns) may be utilized when available.

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. It was used for the first time in Canada shortly after its implementation there when a tornado developed near the town on Shelburne, Ontario on April 18th, 2013, causing up to EF1 damage.

The first time the EF5 rating was used was for the May 4, 2007 Greensburg, Kansas tornado. The latest occurrence of an EF5 tornado was the 2013 Moore tornado in Moore, Oklahoma during the May 18–21, 2013 tornado outbreak.

Parameters[edit]

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.[3]

ScaleWind speed
(Estimated)[4]
Example of damage
mphkm/hm/s
EF0 65–85104–13729–37EF0 damage example--shingles torn from roof
EF1 86–110138–17738–49EF1 damage example -- One story residential home with uplift of roof deck and loss of significant roof covering, garage doors collapsed outward
EF2 111–135178–21750–60EF2 damage example -- School with collapse of roof structure
EF3 136–165218–26661–73EF3 damage example -- Small professional building with collapse of exterior walls while interior wall remain standing
EF4 166–200267–32274–90EF4 damage example -- Single family residence with interior walls and floor above basement missing
EF5 201–240323–38591–105EF5 damage example -- House with not much more than the foundation left


Damage indicators and degrees of damage[edit]

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). Larger degrees of damage done to the damage indicators correspond to higher wind speeds.[5] The links in the right column of the following table describe the degrees of damage for the damage indicators listed in each row.

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

Differences from the Fujita scale[edit]

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 (420–512 km/h), while the new scale lists an EF5 as a tornado with winds above 200 mph (322 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; 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.[5]

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.[3]

Rating classifications[edit]

Tornado rating classifications
EF0EF1EF2EF3EF4EF5
WeakStrongViolent
Significant
Intense

For purposes such as tornado climatology studies, Enhanced Fujita scale ratings may be grouped into classes.[6][7][8]

See also[edit]

References[edit]

  1. ^ "Assessing tornado damage: EF-scale vs. F-scale". The Weather Network. 
  2. ^ "Enhanced Fujita Scale". Environment Canada. 
  3. ^ a b "The Enhanced Fujita Scale (EF Scale)". Storm Prediction Center. 2007-02-02. Retrieved 2009-06-21. 
  4. ^ "Enhanced F Scale for Tornado Damage". Storm Prediction Center. Retrieved 2009-06-21. 
  5. ^ a b McDonald, James; Kishor C. Mehta (October 10, 2006). A recommendation for an Enhanced Fujita scale (EF-Scale). Lubbock, Texas: Wind Science and Engineering Research Center, Texas Tech University. Retrieved 2013-05-21. 
  6. ^ Grazulis, Thomas P. (July 1993). Significant Tornadoes 1680–1991. St. Johnsbury, Vermont: The Tornado Project of Environmental Films. ISBN 1-879362-03-1. 
  7. ^ The Fujita Scale of Tornado Intensity at tornadoproject.com
  8. ^ "Severe Thunderstorm Climatology". National Severe Storms Laboratory, National Oceanic and Atmospheric Administration, US Department of Commerce. 29 March 2013. Retrieved 22 May 2013. 

External links[edit]