Enhanced Fujita Scale
EFU Unknown No surveyable damage
EF0 65–85 mph Light damage
EF1 86–110 mph Moderate damage
EF2 111–135 mph Considerable damage
EF3 136–165 mph Severe damage
EF4 166–200 mph Devastating damage
EF5 >200 mph Incredible damage
The National Weather Service’s arrow showing the EF scale. This includes a description word for each level of the scale.

The Enhanced Fujita scale (abbreviated as EF-Scale) rates tornado intensity based on the severity of the damage they cause. It is used in some countries, including the United States, Canada, France, China, and Mongolia .

The Enhanced Fujita scale replaced the decommissioned Fujita scale that was introduced in 1971 by Ted Fujita.[1] Operational use began in the United States on February 1, 2007, followed by Canada on April 1, 2013.[2][3][4] 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.[5] 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.[6]

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.[7]

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 modeling) 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 the 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 of Shelburne, Ontario, on April 18, 2013, causing up to EF1 damage.[8]

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 windspeeds. Some of these newer methods include mobile doppler radar and forensic engineering.[9]

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.[10]

Scale Wind speed estimate[11] Frequency[12] Potential Damage [6] Example of damage
mph km/h
EFU N/AN/A 3.11% No surveyable damage.
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.[6]		 N/A
EF0 65–85105–137 52.82% Minor damage.
Small trees are blown down and bushes are uprooted. Shingles are ripped off roofs, windows in cars and buildings are blown out, medium to large branches snapped off of large trees, sheds are majorly damaged, and loose small items are tossed and blown away (i.e. lawn chairs, plastic tables, sports equipment, mattresses). Barns are damaged. Paper and leaves lifted off the ground.[13]		 EF0 damage example--This house only sustained 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.
EF1 86–110138–177 32.98% Moderate damage
Roofs stripped from shingles or planting. Small areas of roof may be blown off house. Doors and garage doors blown in, siding ripped off houses, mobile homes flipped or rolled onto their sides, small trees uprooted, large trees snapped or blown down, telephone poles snapped, outhouses and sheds blown away. Cars occasionally flipped or blown over, and moderate roof and side damage to barns. Corn stalks slightly bent and stripped of leaves.		 EF1 damage example--EF1 tornadoes 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.
EF2 111–135178–217 8.41% Considerable damage
Whole roofs ripped off frame houses, interiors of frame homes damaged, and small, medium, and large trees uprooted. Weak structures such as barns, mobile homes, sheds, and outhouses are completely destroyed. Cars are lifted off the ground.		 EF2 damage example--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 completely destroying mobile homes, garages, and barns and generating large amounts of flying debris. This home completely lost its roof, but its walls remained intact.
EF3 136–165218–266 2.18% Severe damage
Roofs and numerous outside walls blown away from frame homes, all trees in its path uprooted or lofted. Two-story homes have their second floor destroyed, high-rises have many windows blown out, radio towers blown down, metal buildings (e.g. factories, power plants, construction sites, etc.) are heavily damaged, sometimes completely destroyed. Large vehicles such as tractors, buses, and forklifts are blown from their original positions. Trains can be flipped or rolled onto their sides. Severe damage to large structures such as shopping malls.		 EF3 damage example--Here, the roof and all but some inner walls of this frame home have been demolished. While taking shelter in a basement, cellar, or inner room improves one's odds of surviving a tornado drastically, occasionally even this is not enough.
EF4 166–200267–322 0.46% Devastating damage
Trees are partially debarked, cars are mangled and thrown in the air, frame homes are completely destroyed and some may be swept away, moving trains blown off railroad tracks, and barns are leveled. High-rises are significantly damaged.		 EF4 damage example--Brick homes get reduced to piles of rubble. Above-ground structures are almost completely vulnerable to EF4 tornadoes, which level well-built structures, toss heavy vehicles through the air, and uproot trees, turning them into flying missiles
EF5 201+323+ 0.05% Incredible damage
Nearly all buildings aside from heavily built structures are destroyed. Cars are mangled and thrown hundreds, possibly thousands of yards away. Frame homes, brick homes, and small businesses, are swept away, trees debarked, corn stalks flattened or ripped out of the ground, skyscrapers sustain major structural damage, grass ripped out of the ground. Wood and any small solid material become dangerous projectiles.		 EF5 damage example--These tornadoes cause complete destruction, obliterating and sweeping away almost anything in their paths, including those sheltering in open basements, sending any vehicles or trains flying through the air, and causing tall buildings to collapse or to have severe structural deformations. Brick, cinderblock, and concrete not immune to becoming projectiles.

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.[14] 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)Maximum degrees of damage
1Small barns or farm outbuildings (SBO) 8[15]
2One- or two-family residences (FR12) 10[16]
3Manufactured home – single wide (MHSW) 9[17]
4Manufactured home – double wide (MHDW)12[18]
5Apartments, condos, townhouses [three stories or less] (ACT) 6[19]
6Motel (M) 10[20]
7Masonry apartment or motel building (MAM) 7[21]
8Small retail building [fast-food restaurants] (SRB) 8[22]
9Small professional building [doctor's office, branch banks] (SPB) 9[23]
10Strip mall (SM) 9[24]
11Large shopping mall (LSM) 9[25]
12Large, isolated retail building [Wal-Mart, Home Depot] (LIRB) 7[26]
13Automobile showroom (ASR) 8[27]
14Automobile service building (ASB) 8[28]
15Elementary school [single-story; interior or exterior hallways] (ES) 10[29]
16Junior or senior high school (JHSH) 11[30]
17Low-rise building [1–4 stories] (LRB) 7[31]
18Mid-rise building [5–20 stories] (MRB) 10[32]
19High-rise building [more than 20 stories] (HRB) 10[33]
20Institutional building [hospital, government or university building] (IB) 11[34]
21Metal building system (MBS)8[35]
22Service station canopy (SSC)6[36]
23Warehouse building [tilt-up walls or heavy-timber construction] (WHB) 7[37]
24Electrical transmission lines (ETL) 6[38]
25Free-standing towers (FST) 3[39]
26Free-standing light poles, luminary poles, flag poles (FSP) 3[40]
27Trees: hardwood (TH) 5[41]
28Trees: softwood (TS) 5[42]

Differences from the Fujita scale

The new 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.[43] 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 in the United States recorded before February 1, 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.[14] 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 be rated EF4 or lower on the Enhanced Fujita scale.[44]

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 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.[10]

Rating classifications

Tornado rating classifications
EF0 EF1 EF2 EF3 EF4 EF5
Weak Moderate Strong Severe Extreme Catastrophic
Weak Strong Violent
Significant
Intense

For purposes such as tornado climatology studies, Enhanced Fujita scale ratings may be grouped into classes.[45][46][47] 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 use a modified EF scale wording, which gives a new term for each rating on the scale, going from weak to catastrophic.[48]

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

See also

References

  1. ↑ 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.
  2. ↑ "Fujita Tornado Damage Scale". www.spc.noaa.gov.
  3. ↑ "Tornado Scale - The Enhanced Fujita Scale | TornadoFacts.net". www.tornadofacts.net.
  4. ↑ "Enhanced Fujita Scale". Environment Canada. May 10, 2013.
  5. ↑ https://www.keraunos.org/recherche/comprendre-les-orages-pedagogie-vulgarisation/tornades-trombes-tubas/intensite-tornade-echelle-fujita-amelioree-ef-f-scale.html
  6. 1 2 Murphy, John D. (July 9, 2018). "National Weather Service Instruction 10-1605" (PDF). National Weather Service. pp. A–74–75. Retrieved November 29, 2019.
  7. ↑ "Enhanced Fujita Scale - Tornado Damage Scale". factsjustforkids.com. Retrieved June 14, 2019.
  8. ↑ "Tornado to Be 1st Assessed by New Scale". The Washington Post. Associated Press. February 2, 2007. Retrieved July 11, 2009.
  9. ↑ Marshall, Tim & Brown-Giammanco, Tanya & Krautwurst, Samantha & Toledo, Nicholas. (2022). On the Current Revision of the Enhanced Fujita (EF) Scale.
  10. 1 2 "The Enhanced Fujita Scale (EF Scale)". Storm Prediction Center. February 1, 2007. Retrieved June 21, 2009.
  11. ↑ "Enhanced F Scale for Tornado Damage". Storm Prediction Center. Retrieved June 21, 2009.
  12. ↑ "Storm Prediction Center WCM Data". Storm Prediction Center. Retrieved September 15, 2021.
  13. ↑ "Garrett's Blog: Mobile Home Tornado Risk". 5newsonline.com. February 28, 2013. Retrieved September 30, 2020.
  14. 1 2 McDonald, James; Kishor C. Mehta (October 10, 2006). A recommendation for an Enhanced Fujita scale (EF-Scale) (PDF). Lubbock, Texas: Wind Science and Engineering Research Center, Texas Tech University. Retrieved May 21, 2013.
  15. ↑ c:File:EF DI1 (SBO).jpg
  16. ↑ c:File:EF DI2 (FR12).jpg
  17. ↑ c:File:EF DI3 (MHSW).jpg
  18. ↑ c:File:EF DI4 (MHDW).jpg
  19. ↑ c:File:EF DI5 (ACT).jpg
  20. ↑ c:File:EF DI6 (M).jpg
  21. ↑ c:File:EF DI7 (MAM).jpg
  22. ↑ c:File:EF DI8 (SRB).jpg
  23. ↑ c:File:EF DI9 (SPB).jpg
  24. ↑ c:File:EF DI10 (SM).jpg
  25. ↑ c:File:EF DI11 (LSM).jpg
  26. ↑ c:File:EF DI12 (LIRB).jpg
  27. ↑ c:File:EF DI13 (ASR).jpg
  28. ↑ c:File:EF DI14 (ASB).jpg
  29. ↑ c:File:EF DI15 (ES).jpg
  30. ↑ c:File:EF DI16 (JHSH).jpg
  31. ↑ c:File:EF DI17 (LRB).jpg
  32. ↑ c:File:EF DI18 (MROB).jpg
  33. ↑ c:File:EF DI19 (HROB).jpg
  34. ↑ c:File:EF DI20 (IB).jpg
  35. ↑ c:File:EF DI21 (MBS).jpg
  36. ↑ c:File:EF DI22 (SSC).jpg
  37. ↑ c:File:EF DI23 (WHB).jpg
  38. ↑ c:File:EF DI 24 (ETL).jpg
  39. ↑ c:File:EF DI25 (FST).jpg
  40. ↑ c:File:EF DI26 (FSP).jpg
  41. ↑ c:File:EF DI27 (TH).jpg
  42. ↑ c:File:EF DI28 (TS).jpg
  43. ↑ Wind Science and Engineering Center. (2006). A recommendation for an enhanced Fujita scale (EF-scale). Retrieved from National Weather Service Storm Prediction Center website https://www.spc.noaa.gov
  44. ↑ Doswell, Charles A.; Brooks, Harold E.; Dotzek, Nikolai (July 2009). "On the Implementation of the Enhanced Fujita Scale in the USA" (PDF). Atmospheric Research. 93 (1–3): 556–557. Bibcode:2009AtmRe..93..554D. doi:10.1016/j.atmosres.2008.11.003. Retrieved January 20, 2020.
  45. ↑ Grazulis, Thomas P. (July 1993). Significant Tornadoes 1680–1991. St. Johnsbury, Vermont: The Tornado Project of Environmental Films. ISBN 1-879362-03-1.
  46. ↑ The Fujita Scale of Tornado Intensity Archived December 30, 2011, at the Wayback Machine at tornadoproject.com
  47. ↑ "Severe Thunderstorm Climatology". National Severe Storms Laboratory, National Oceanic and Atmospheric Administration, US Department of Commerce. March 29, 2013. Archived from the original on October 4, 2012. Retrieved May 22, 2013.
  48. ↑ "The Tornado Outbreak of March 31, 2023". National Weather Service Quad Cities. Retrieved July 21, 2023.
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