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Enhanced Fujita Scale
EF0 EF1 EF2 EF3 EF4 EF5

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

Implemented in place of the Fujita scale introduced in 1971 by Ted Fujita, 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 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 (e.g., detailed physical or any numerical modelling) owing to excessive cost, the wind speeds were attained 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 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. The first time the EF5 assessment was used was the Greensburg, Kansas tornado that occurred on May 4, 2007.

Contents

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, one must look up the damage indicator (the type of structure which has been damaged) and consult the degrees of damage associated for that particular indicator.[1]

Scale Wind speed Relative frequency Potential damage
mph km/h
EF0 65–85 105–137 53.5% Minor damage.

Peels surface off some roofs; some damage to gutters or siding; branches broken off trees; shallow-rooted trees pushed over.

Confirmed tornadoes with no reported damage (i.e., those that remain in open fields) are always rated EF0.

EF0 damage example
EF1 86–110 138–178 31.6% Moderate damage.

Roofs severely stripped; mobile homes overturned or badly damaged; loss of exterior doors; windows and other glass broken.

EF1 damage example
EF2 111–135 179–218 10.7% Considerable damage.

Roofs torn off well-constructed houses; foundations of frame homes shifted; mobile homes completely destroyed; large trees snapped or uprooted; light-object missiles generated; cars lifted off ground.

EF2 damage example
EF3 136–165 219–266 3.4% Severe damage.

Entire stories of well-constructed houses destroyed; severe damage to large buildings such as shopping malls; trains overturned; trees debarked; heavy cars lifted off the ground and thrown; structures with weak foundations blown away some distance.

EF3 damage example
EF4 166–200 267–322 0.7% Devastating damage.

Well-constructed houses and whole frame houses completely leveled; cars thrown and small missiles generated.

EF4 damage example
EF5 >200 >322 <0.1% Extreme damage.

Strong frame houses leveled off foundations and swept away; automobile-sized missiles fly through the air in excess of 100 m (300 ft); steel reinforced concrete structure badly damaged; high-rise buildings have significant structural deformation.

EF5 damage example

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.[2]

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 new scale lists an EF5 as a tornado with winds at or 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 weren't 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" 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, will have their own DIs and DODs. Damage descriptors and wind speeds will also be readily updated as new information is learned.[2]

Since the new system will still use 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]

See also

References

  1. ^ "Enhanced F Scale for Tornado Damage". Storm Prediction Center. http://www.spc.noaa.gov/efscale/ef-scale.html. Retrieved 2009-06-21. 
  2. ^ a b McDonald, James; Kishor C. Mehta (10 October 2006). A Recommendation for an Enhanced Fujita Scale (EF-Scale). Lubbock, Texas: Wind Science and Engineering Research Center. http://www.wind.ttu.edu/EFScale.pdf. Retrieved 2009-06-21. 
  3. ^ "The Enhanced Fujita Scale (EF Scale)". Storm Prediction Center. 2007-02-02. http://www.spc.noaa.gov/efscale/. Retrieved 2009-06-21. 

External links


Enhanced Fujita Scale
EF0 EF1 EF2 EF3 EF4 EF5

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

Implemented in place of the Fujita scale introduced in 1971 by Ted Fujita, 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 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 (e.g., 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 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. The first time the EF5 assessment was used was the Greensburg, Kansas tornado that occurred on May 4, 2007.

Contents

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, one must look up the damage indicator (the type of structure which has been damaged) and consult the degrees of damage associated for that particular indicator.[1]

Scale Wind speed Relative frequency Potential damage
mph km/h
EF0 65–85 105–137 53.5% Minor damage.

Peels surface off some roofs; some damage to gutters or siding; branches broken off trees; shallow-rooted trees pushed over.

Confirmed tornadoes with no reported damage (i.e., those that remain in open fields) are always rated EF0.

EF1 86–110 138–178 31.6% Moderate damage.

Roofs severely stripped; mobile homes overturned or badly damaged; loss of exterior doors; windows and other glass broken.

EF2 111–135 179–218 10.7% Considerable damage.

Roofs torn off well-constructed houses; foundations of frame homes shifted; mobile homes completely destroyed; large trees snapped or uprooted; light-object missiles generated; cars lifted off ground.

EF3 136–165 219–266 3.4% Severe damage.

Entire stories of well-constructed houses destroyed; severe damage to large buildings such as shopping malls; trains overturned; trees debarked; heavy cars lifted off the ground and thrown; structures with weak foundations blown away some distance.

EF4 166–200 267–322 0.7% Extreme damage.

Well-constructed houses and whole frame houses completely leveled; cars thrown and small missiles generated.

EF5 >200 >322 <0.1% Massive Damage.

Strong frame houses leveled off foundations and swept away; steel-reinforced concrete structures critically damaged; high-rise buildings have severe structural deformation. Incredible phenomena will occur.

Enhanced Fujita Tornado Scale Compared to Saffir-Simpson Hurricane Scale

When compared to the Saffir-Simpson Hurricane Scale, an EF0 tornado would be roughly equivalent in terms of wind speed to an upper-level tropical storm (66-73 mph) or a Category 1 hurricane (74–85 mph). An EF1 would be equivalent to a hurricane in the upper Category 1 (86-95 mph) to Category 2 (96–110 mph) range; an EF2 would be akin to a hurricane ranging from a Category 3 (111-130 mph) to a lower Category 4 (132-135 mph). An EF3 tornado would be roughly equivalent to an upper Category 4 (136-155 mph) or lower Category 5 hurricane (156-165 mph). Tornadoes of EF4 strength would be as powerful as an upper Category 5 hurricane (>166 mph).

There is no Category 6 on the Saffir-Simpson hurricane scale, but if there were, an EF5 tornado would essentially equal a Category 6, with winds well over 200 mph. The most powerful Category 5 Atlantic hurricanes on record were Hurricane Gilbert in 1988 with sustained winds of 215 mph. By comparison, the most powerful tornado on record was an F5 that tore through Oklahoma in 1999. Doppler weather radar detected winds at an incredible 318 mph, easily eclipsing the previous record set by a 1993 F5 twister with winds between 257 and 268 mph that also struck Oklahoma.

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.[2]

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 new scale lists an EF5 as a tornado with winds at or 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 weren't 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" 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, will have their own DIs and DODs. Damage descriptors and wind speeds will also be readily updated as new information is learned.[2]

Since the new system will still use 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]

See also

References

  1. ^ "Enhanced F Scale for Tornado Damage". Storm Prediction Center. http://www.spc.noaa.gov/efscale/ef-scale.html. Retrieved 2009-06-21. 
  2. ^ a b McDonald, James; Kishor C. Mehta (10 October 2006). A Recommendation for an Enhanced Fujita Scale (EF-Scale). Lubbock, Texas: Wind Science and Engineering Research Center. http://www.wind.ttu.edu/EFScale.pdf. Retrieved 2009-06-21. 
  3. ^ "The Enhanced Fujita Scale (EF Scale)". Storm Prediction Center. 2007-02-02. http://www.spc.noaa.gov/efscale/. Retrieved 2009-06-21. 

External links


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