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 Enhanced Fujita Scale, or EF Scale, is the scale for rating the strength of tornadoes in the United States estimated via the damage they cause.
Implemented in place of the Fujita scale introduced in 1971, 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 as well as 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 2000-2004 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 measurement was used was the Greensburg, KS tornado 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 legacy descriptions which more or less remain accurate, however, for the EF scale, one must consult the respective damage indicator and associated degrees of damage.[1]
Category EF0 | Wind speed | 65–85 mph | 105–137 km/h | |
Potential 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. | |||
Category EF1 | Wind speed | 86–110 mph | 138–178 km/h | |
Potential damage | ![]() Roofs severely stripped; mobile homes overturned or badly damaged; loss of exterior doors; windows and other glass broken. | |||
Category EF2 | Wind speed | 111–135 mph | 179–218 km/h | |
Potential 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. | |||
Category EF3 | Wind speed | 136–165 mph | 219–266 km/h | |
Potential 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. | |||
Category EF4 | Wind speed | 166–200 mph | 267–322 km/h | |
Potential damage | ![]() Well-constructed houses and whole frame houses completely leveled; cars thrown and small missiles generated. | |||
Category EF5 | Wind speed | >200 mph | >322 km/h | |
Potential damage | ![]() Strong frame houses leveled off foundations and swept away; automobile-sized missiles fly through the air in excess of 100 m (109 yd); high-rise buildings have significant structural deformation; incredible phenomena will occur. So far only one EF5 tornado has been recorded since the Enhanced Fujita Scale was introduced on February 1, 2007. See Greensburg, Kansas tornado |
Damage Indicators and Degrees of Damage
The EF Scale currently has 28 Damage Indicators (DI), or types of structures and vegetation, with varying numbers 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 descriptors; 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
- Fujita scale
- TORRO scale
- Beaufort scale
- Saffir-Simpson Hurricane Scale
- Tornado intensity and damage
- List of tornadoes and tornado outbreaks
- List of EF5 tornadoes
- Severe weather terminology
References
- ^ "Enhanced F Scale for Tornado Damage". Storm Prediction Center.
- ^ a b McDonald, James (10 October 2006). A Recommendation for an Enhanced Fujita Scale (EF-Scale) (PDF). Lubbock, Texas: Wind Science and Engineering Research Center.
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External links
![](http://upload.wikimedia.org/wikipedia/en/thumb/4/4a/Commons-logo.svg/30px-Commons-logo.svg.png)
- NOAA National Weather Service Improves Tornado Rating System (NOAA News)
- The Enhanced Fujita Scale (EF Scale) (NOAA / SPC)
- Fujita Scale Enhancement Project (Wind Science and Engineering Research Center at Texas Tech University)
- Symposium on the F-Scale and Severe-Weather Damage Assessment (American Meteorological Society)
- A Guide to F-Scale Damage Assessment (NWS)
- A Guide for Conducting Convective Windstorm Surveys (NWS SR146)
- The Tornado: An Engineering-Oriented Perspective (NWS SR147)
- The Fujita Scale of Tornado Intensity (The Tornado Project)
- Mitigation Assessment Team Report: Midwest Tornadoes of May 3, 1999 (FEMA)