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 (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 and France [1] The EF scale is also unofficially used in other countries including China [2] .
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. [3]
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 Enhanced Fujita scale replaced the decommissioned Fujita scale that was introduced in 1971 by Ted Fujita. [4] Operational use began in the United States on February 1, 2007, followed by Canada on April 1, 2013, who uses a modified verion known as the CEF-scale. [5] [6] [7] 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. [8] Similarly, the Japanese implementation of the scale is also modified along similar lines; the Japanese variant is referred to locally in Japan as the JEF or Japanese Enhanced Fujita Scale. [9] The scale is also used unofficially in other countries, such as China. [10]
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. [11]
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. A different variation of the scale 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 CEF1 damage. [12]
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. [13]
In 2024, Anthony W. Lyza, Matthew D. Flournoy, and A. Addison Alford, researchers with the National Severe Storms Laboratory, Storm Prediction Center, CIWRO, and the University of Oklahoma's School of Meteorology, published a paper stating, ">20% of supercell tornadoes may be capable of producing EF4–EF5 damage". [14]
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. [15]
Scale | Wind speed estimate [16] | Frequency [17] | Potential Damage | Example of damage | |
---|---|---|---|---|---|
mph | km/h | ||||
EFU | N/A | N/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. [3] | N/A |
EF0 | 65–85 | 105–137 | 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. [18] | |
EF1 | 86–110 | 138–177 | 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. | |
EF2 | 111–135 | 178–217 | 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. | |
EF3 | 136–165 | 218–266 | 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. | |
EF4 | 166–200 | 267–322 | 0.45% | 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. | |
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. |
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. [19] 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 |
---|---|---|
1 | Small barns or farm outbuildings (SBO) | 8 [20] |
2 | One- or two-family residences (FR12) | 10 [21] |
3 | Manufactured home – single wide (MHSW) | 9 [22] |
4 | Manufactured home – double wide (MHDW) | 12 [23] |
5 | Apartments, condos, townhouses [three stories or less] (ACT) | 6 [24] |
6 | Motel (M) | 10 [25] |
7 | Masonry apartment or motel building (MAM) | 7 [26] |
8 | Small retail building [fast-food restaurants] (SRB) | 8 [27] |
9 | Small professional building [doctor's office, branch banks] (SPB) | 9 [28] |
10 | Strip mall (SM) | 9 [29] |
11 | Large shopping mall (LSM) | 9 [30] |
12 | Large, isolated retail building [Wal-Mart, Home Depot] (LIRB) | 7 [31] |
13 | Automobile showroom (ASR) | 8 [32] |
14 | Automobile service building (ASB) | 8 [33] |
15 | Elementary school [single-story; interior or exterior hallways] (ES) | 10 [34] |
16 | Junior or senior high school (JHSH) | 11 [35] |
17 | Low-rise building [1–4 stories] (LRB) | 7 [36] |
18 | Mid-rise building [5–20 stories] (MRB) | 10 [37] |
19 | High-rise building [more than 20 stories] (HRB) | 10 [38] |
20 | Institutional building [hospital, government or university building] (IB) | 11 [39] |
21 | Metal building system (MBS) | 8 [40] |
22 | Service station canopy (SSC) | 6 [41] |
23 | Warehouse building [tilt-up walls or heavy-timber construction] (WHB) | 7 [42] |
24 | Electrical transmission lines (ETL) | 6 [43] |
25 | Free-standing towers (FST) | 3 [44] |
26 | Free-standing light poles, luminary poles, flag poles (FSP) | 3 [45] |
27 | Trees: hardwood (TH) | 5 [46] |
28 | Trees: softwood (TS) | 5 [47] |
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. [48] 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. [19] 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. [49]
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. [15]
EF0 | EF1 | EF2 | EF3 | EF4 | EF5 |
---|---|---|---|---|---|
Weak | Moderate | Strong | Severe | Extreme | Catastrophic |
Weak | Strong | Violent | |||
Significant | |||||
Intense |
This section needs expansion. You can help by adding to it. (May 2013) |
This section needs additional citations for verification .(January 2023) |
For purposes such as tornado climatology studies, Enhanced Fujita scale ratings may be grouped into classes. [50] [51] [52] 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. [53]
The table shows other variations of the tornado rating classifications based on certain areas.
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. The official Fujita scale category is determined by meteorologists and engineers after a ground or aerial damage survey, or both; and depending on the circumstances, ground-swirl patterns, weather radar data, witness testimonies, media reports and damage imagery, as well as photogrammetry or videogrammetry if motion picture recording is available. The Fujita scale was replaced with the Enhanced Fujita scale (EF-Scale) in the United States in February 2007. In April 2013, Canada adopted the EF-Scale over the Fujita scale along with 31 "Specific Damage Indicators" used by Environment Canada (EC) in their ratings.
The TORRO tornado intensity scale is a scale measuring tornado intensity between T0 and T11. It was proposed by Terence Meaden of the Tornado and Storm Research Organisation (TORRO), a meteorological organisation in the United Kingdom, as an extension of the Beaufort scale.
From April 2–3, 1956, a large, deadly tornado outbreak affected the Great Plains, parts of the South, and the upper Midwest in the contiguous United States, especially the Great Lakes region. The outbreak produced at least 55 tornadoes, including an F5 that devastated the Grand Rapids metropolitan area in the U.S. state of Michigan on April 3. It was one of three tornadoes to move across southwest Lower Michigan on that day. A fourth tornado struck north of the Manistee area, in the northern part of the peninsula. The Hudsonville–Standale tornado killed 18 and injured 333. It remains the fourth deadliest tornado on record in Michigan and is the most recent F5 on record there. Several other deadly, intense, long-tracked tornadoes also occurred during the outbreak. In addition to the fatalities in Kansas, Oklahoma, Michigan and Berlin, Wisconsin, three people were killed in Tennessee, one person in Kentucky and two more people in Wisconsin. In total, 39 were killed during the entire event.
Tornado intensity is the measure of wind speeds and potential risk produced by a tornado. Intensity can be measured by in situ or remote sensing measurements, but since these are impractical for wide-scale use, intensity is usually inferred by proxies, such as damage. The Fujita scale, Enhanced Fujita scale, and the International Fujita scale rate tornadoes by the damage caused. In contrast to other major storms such as hurricanes and typhoons, such classifications are only assigned retroactively. Wind speed alone is not enough to determine the intensity of a tornado. An EF0 tornado may damage trees and peel some shingles off roofs, while an EF5 tornado can rip well-anchored homes off their foundations, leaving them bare— even deforming large skyscrapers. The similar TORRO scale ranges from a T0 for extremely weak tornadoes to T11 for the most powerful known tornadoes. Doppler radar data, photogrammetry, and ground swirl patterns may also be analyzed to determine the intensity and assign a rating.
A violent severe weather outbreak struck the Southeast on April 4–5, 1977. A total of 22 tornadoes touched down with the strongest ones occurring in Mississippi, Alabama, and Georgia. The strongest was a catastrophic F5 tornado that struck the northern Birmingham, Alabama, suburbs during the afternoon of Monday, April 4. In addition to this tornado, several other tornadoes were reported from the same system in the Midwest, Alabama, Georgia, Mississippi and North Carolina. One tornado in Floyd County, Georgia, killed one person, and another fatality was reported east of Birmingham in St. Clair County. In the end, the entire outbreak directly caused 24 deaths and 158 injuries. The storm system also caused the crash of Southern Airways Flight 242, which killed 72 and injured 22.
During the evening of June 22, 2007, a powerful F5 tornado struck the town of Elie, in the Canadian province of Manitoba. It was part of a small two-day tornado outbreak that occurred in the area and reached a maximum width of 150 yards (140 m). The tornado was unusual because it caused the extreme damage during its roping out stage at a mere 35 yards (32 m) in width and moved extremely slowly and unpredictably. The tornado tracked primarily southeast, as opposed to the usual northeast, and made multiple loops and sharp turns. Because Environment Canada adopted the Enhanced Fujita scale in 2013, there will be no more tornadoes with an F5 rating, making this tornado the first and last confirmed F5 tornado in Canada.
On June 3–4, 1958, a destructive tornado outbreak affected the Upper Midwestern United States. It was the deadliest tornado outbreak in the U.S. state of Wisconsin since records began in 1950. The outbreak, which initiated in Central Minnesota, killed at least 28 people, all of whom perished in Northwestern Wisconsin. The outbreak generated a long-lived tornado family that produced four intense tornadoes across the Eau Claire–Chippewa Falls metropolitan area, primarily along and near the Chippewa and Eau Claire rivers. The deadliest tornado of the outbreak was a destructive F5 that killed 21 people and injured 110 others in and near Colfax, Wisconsin.
Tornadoes are more common in the United States than in any other country or state. The United States receives more than 1,200 tornadoes annually—four times the amount seen in Europe. Violent tornadoes—those rated EF4 or EF5 on the Enhanced Fujita Scale—occur more often in the United States than in any other country.
On December 18–20, 1957, a significant tornado outbreak sequence affected the southern Midwest and the South of the contiguous United States. The outbreak sequence began on the afternoon of December 18, when a low-pressure area approached the southern portions of Missouri and Illinois. Supercells developed and proceeded eastward at horizontal speeds of 40 to 45 miles per hour, yielding what was considered the most severe tornado outbreak in Illinois on record so late in the calendar year. Total losses in the state were estimated to fall within the range of $8–$10 million.
The following is a glossary of tornado terms. It includes scientific as well as selected informal terminology.
From April 2–3, 1982, a major tornado outbreak resulted in over 60 tornadoes and 30 fatalities, primarily over portions of Northeast Texas and Southwest Arkansas, as well as Southeastern Oklahoma. Three of the tornadoes were rated F4, and one officially was recorded as an F5 near Broken Bow, Oklahoma, all on April 2. Beginning on April 2, a series of tornado-producing supercells formed across portions of northeastern Texas and southeastern Oklahoma. One produced an F5 tornado, the first since April 4, 1977, which crossed mostly rural areas near Speer and Broken Bow, and deposited a motel sign from Broken Bow 30 miles (48 km) away in Arkansas. However, reanalysis a decade later found the rating to be lower, owing to unsound construction practices. The F5 tornado resulted in no fatalities, but an F4 tornado in Paris, Texas, resulted in 10 fatalities and 170 injuries. Additionally, the Storm Prediction Center, known then as the Severe Local Storms Unit, issued its first officially documented high risk on April 2, as well as the first tornado watch to contain the wording Particularly Dangerous Situation (PDS).
The International Fujita scale rates the intensity of tornadoes and other wind events based on the severity of the damage they cause. It is used by the European Severe Storms Laboratory (ESSL) and various other organizations including Deutscher Wetterdienst (DWD) and State Meteorological Agency (AEMET). The scale is intended to be analogous to the Fujita and Enhanced Fujita scales, while being more applicable internationally by accounting for factors such as differences in building codes.
The history of tornado research spans back centuries, with the earliest documented tornado occurring in 200 and academic studies on them starting in the 18th century. This is a timeline of government or academic research into tornadoes.