Tornado intensity and damage
Encyclopedia
The Fujita scale
and the Enhanced Fujita Scale
rate tornadoes by damage caused. The Enhanced Fujita Scale was an upgrade to the older Fujita scale, with engineered (by expert elicitation
) wind estimates and better damage descriptions, but was designed so that a tornado rated on the Fujita scale would receive the same numerical rating. An EF0 tornado will probably damage trees but not substantial structures, whereas an EF5 tornado can rip buildings off their foundations leaving them bare and even deform large skyscraper
s. 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 (cycloidal marks) may also be analyzed to determine intensity and award a rating.
Tornadoes vary in intensity regardless of shape, size, and location, though strong tornadoes are typically larger than weak tornadoes. The association with track length and duration also varies, although longer track tornadoes tend to be stronger. In the case of violent tornadoes, only a small portion of the path is of violent intensity, most of the higher intensity from subvortices
.
In the United States, 80% of tornadoes are EF0 and EF1 (T0 through T3) tornadoes. The rate of occurrence drops off quickly with increasing strength—less than 1% are violent tornadoes(EF4, T8 or stronger).
. One can still find these incorrect guesses in some old (until 1960s) literature, such as the original Fujita Intensity Scale.
In 1971, Dr. Tetsuya Theodore Fujita
introduced the idea for a scale of tornado winds. With the help of colleague Allen Pearson
, he created and introduced what came to be called the Fujita scale
in 1973. This is what the F stands for in F1, F2, etc. The scale was based on a relationship between the Beaufort scale
and the Mach number
scale; the low end of F1 on his scale corresponds to the low end of B12 on the Beaufort scale, and the low end of F12 corresponds to the speed of sound at sea level, or Mach 1. In practice, tornadoes are only assigned categories F0 through F5.
The TORRO scale
, created by the Tornado and Storm Research Organisation (TORRO)
, was developed in 1974, and published a year later. The TORRO scale has 12 levels, which cover a broader range with tighter graduations. It ranges from a T0 for extremely weak tornadoes to T11 for the most powerful known tornadoes. T0-T1 roughly correspond to F0, T2-T3 to F1, and so on. While T10+ would be approximately an F5, the highest tornado rated to date on the TORRO scale was a T8. There is some debate as to the usefulness of the TORRO scale over the Fujita scale—while it may be helpful for statistical purposes to have more levels of tornado strength, often the damage caused could be created by a large range of winds, rendering it hard to narrow the tornado down to a single TORRO scale category.
Research conducted in the late 1980s and 1990s suggested that, even with the implication of the Fujita scale, tornado winds were notoriously overestimated, especially in significant and violent tornadoes. Because of this, in 2006, the American Meteorological Society
introduced the Enhanced Fujita Scale
, to help assign realistic wind speeds to tornado damage. The scientists specifically designed the scale so that a tornado assessed on the Fujita scale and the Enhanced Fujita scale would receive the same ranking. The EF-scale is more specific in detailing the degrees of damage on different types of structures for a given wind speed. While the F-scale goes from F0 to F12 in theory, the EF-scale is capped at EF5, which is defined as "winds ≥ 200 mph (≥ 320 km/h)". In the United States, the Enhanced Fujita scale went into effect on February 2, 2007 for tornado damage assessments and the Fujita scale is no longer used.
The first observation which confirmed that F5 winds could occur happened on April 26, 1991. A tornado near Red Rock, Oklahoma was monitored by scientists using a portable Doppler radar, an experimental radar device that measures wind speed. Near the tornado's peak intensity, they recorded a wind speed of 115–120 m/s (257-268 mph or 414–432 km/h). Though the portable radar had uncertainty of ± 5–10 m/s (± 11-22 mph or ± 18–36 km/h), this reading was probably within the F5 range, confirming that tornadoes were capable of violent winds found nowhere else on earth.
Eight years later, during the 1999 Oklahoma tornado outbreak of May 3, 1999, another scientific team was monitoring an exceptionally violent tornado (one which would eventually kill 36 people in the area near Moore, Oklahoma
). At about 7:00 pm, they recorded one measurement of 301±20 mph (484±32 km/h), 50 mi/h faster than the previous record. Though this reading is just short of the theoretical F6 rating, the measurement was taken more than 100 feet (30.5 m) in the air, where winds are typically stronger than at the surface. In rating tornadoes, only surface wind speeds, or the wind speeds indicated by the damage resulting from the tornado, are taken into account. Also, in practice, the F6 rating is not used.
While scientists have long theorized that extremely low pressures might occur in the center of tornadoes, there were no measurements to confirm it. A few home barometer
s had survived close passes by tornadoes, recording values as low as 24 in Hg (810 mbar), but these measurements were highly uncertain. However, on June 24, 2003, a group of researchers successfully dropped devices called "turtles" into an F4 tornado near Manchester, South Dakota
, one of which measured a pressure drop of more than 100 mbar as the tornado passed directly overhead. Still, tornadoes are widely varied, so meteorologists are still conducting research to determine if these values are typical or not.
F5 and EF5 tornadoes are exceptionally rare, occurring on average once every few years. The last confirmed F5 tornado anywhere in the world was the Elie, Manitoba Tornado
in Canada, on June 22, 2007. Before that, the last confirmed F5 was the Moore, Oklahoma tornado, which killed 36 people on May 3, 1999. Eight EF5 tornadoes have occurred in the United States, in Greensburg, Kansas
on May 4, 2007; Parkersburg, Iowa
on May 25, 2008; Smithville, Mississippi
, Philadelphia, Mississippi
, Hackleburg, Alabama
and Rainsville, Alabama
(four separate tornadoes) on April 27, 2011; Joplin, Missouri
on May 22, 2011 and El Reno, Oklahoma
on May 24, 2011.
A typical tornado has winds of 110 mph (175 km/h) or less, is approximately 250 feet (75 m) across, and travels a mile (1.6 km) or so before dissipating. However, tornadic behavior is extremely variable; these figures represent only statistical probability.
Two tornadoes that look almost exactly the same can produce drastically different effects. Also, two tornadoes which look very different can produce similar damage. This is due to the fact that tornadoes form by several different mechanisms, and also that they follow a life cycle which causes the same tornado to change in appearance over time. People in the path of a tornado should never attempt to determine its strength as it approaches. Between 1997 and 2005 in the United States, 38 people were killed by EF1 tornadoes, and 3 were killed by EF0 tornadoes. Even the weakest tornado can kill.
The vast majority of tornadoes are designated EF1 or EF0, also known as "weak" tornadoes. However, weak is a relative term for tornadoes, as even these can cause significant damage. F0 and F1 tornadoes are typically short-lived—since 1980 almost 75% of tornadoes rated weak stayed on the ground for one mile (1.6 km) or less. However, in this time, they can cause both damage and fatalities.
EF0 (T0-T1) damage is characterized by superficial damage to structures and vegetation. Well-built structures are typically unscathed, sometimes sustaining broken windows, with minor damage to roofs and chimney
s. Billboards and large signs can be knocked down. Trees may have large branches broken off, and can be uprooted if they have shallow roots. Any tornado that is confirmed but causes no damage (i.e. remains in open fields) is always rated EF0 as well.
EF1 (T2-T3) damage has caused significantly more fatalities than that caused by EF0 tornadoes. At this level, damage to mobile homes and other temporary structures becomes significant, and cars and other vehicles can be pushed off the road. Permanent structures can suffer major damage to their roofs.
EF2 (T4-T5) tornadoes are the lower end of "significant", and yet are stronger than most tropical cyclone
s (though tropical cyclones affect a much larger area and their winds take place for a much longer duration). Well-built structures can suffer serious damage, including roof loss and collapse of outer walls. Mobile homes, however, are almost totally destroyed. Vehicles can be lifted off the ground, and lighter objects can become small missile
s, causing damage outside of the tornado's main path. Wooded areas will have a large percentage of their trees snapped or uprooted.
EF3 (T6-T7) damage is a serious risk to life and limb and the point at which a tornado statistically becomes significantly more destructive and deadly. Few parts of affected buildings are left standing; well-built structures lose all outer and most inner walls. Small vehicles and similarly sized objects are lifted off the ground and tossed as projectiles. Wooded areas will suffer almost total loss of vegetation. Statistically speaking, EF3 is the maximum level that allows for reasonably effective residential sheltering in place in a first floor interior room, closest to the center of the house (the most widespread tornado sheltering procedure in America for those with no basement). Although reasonably effective against tornadoes EF0-2, EF3+ represents the point at which no home can expect to retain any interior walls to shield the occupants, and thus those sheltering above ground will face a high likelihood of severe injury or death as the structure is ripped apart.
EF4 (T8-T9) damage typically results in a total loss of the affected structure. Well-built homes are reduced to a short pile of medium-sized debris on the foundation. Large, heavy vehicles, including airplane
s, train
s, and large truck
s, can be pushed over, flipped repeatedly or picked up and moved short distances. Large, healthy trees are entirely debarked and snapped off close to the ground or uprooted altogether and turned into flying projectiles. Passenger cars and similarly sized objects can be picked up and flung for considerable distances. EF4 damage can be expected to level even the most robustly built homes, making the common practice of sheltering in an interior room on the ground floor of a residence insufficient to ensure survival. A storm shelter, reinforced basement or other subterranean shelter is considered necessary to provide any reasonable expectation of safety against EF4 damage.
EF5 (T10+) damage represents the upper limit of tornado power, and destruction is almost always total. An EF5 tornado pulls well-built homes off their foundations and into the air before shredding them, flinging the wreckage for miles and sweeping the foundation clean. Very little recognizable structural debris is generated by EF5 damage, with most materials reduced to a coarse mix of small, granular particles and dispersed evenly across the tornado's damage path. Large, multi-ton steel frame vehicles and farm equipment are often mangled beyond recognition and deposited miles away or reduced entirely to unrecognizable component parts. The official description of this damage highlights the extreme nature of the destruction, noting that "incredible phenomena will occur"; historically, this has included such awesome displays of power as twisting skyscrapers
, levelling entire communities, and stripping asphalt from roadbeds. Despite their relative rarity, the damage caused by EF5 tornadoes represents a disproportionately extreme hazard to life and limb— since 1950 in the United States, only 58 tornadoes (0.1% of all reports) have been designated F5 or EF5, and yet these have been responsible for more than 1300 deaths and 14,000 injuries (21.5% and 13.6%, respectively).
Fujita scale
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...
and the Enhanced Fujita Scale
Enhanced Fujita Scale
The Enhanced Fujita 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:...
rate tornadoes by damage caused. The Enhanced Fujita Scale was an upgrade to the older Fujita scale, with engineered (by expert elicitation
Expert elicitation
In science, engineering, and research, expert elicitation is the synthesis of opinions of experts of a subject where there is uncertainty due to insufficient data or when such data is unattainable because of physical constraints or lack of resources. Expert elicitation is essentially a scientific...
) wind estimates and better damage descriptions, but was designed so that a tornado rated on the Fujita scale would receive the same numerical rating. An EF0 tornado will probably damage trees but not substantial structures, whereas an EF5 tornado can rip buildings off their foundations leaving them bare and even deform large skyscraper
Skyscraper
A skyscraper is a tall, continuously habitable building of many stories, often designed for office and commercial use. There is no official definition or height above which a building may be classified as a skyscraper...
s. The similar TORRO scale
TORRO scale
The TORRO tornado intensity scale is a scale measuring tornado intensity between T0 and T11. It was developed by Terence Meaden of the Tornado and Storm Research Organisation , a meteorological organisation in the United Kingdom, as an extension of the Beaufort scale.- History and derivation from...
ranges from a T0 for extremely weak tornadoes to T11 for the most powerful known tornadoes. Doppler
Pulse-doppler radar
Pulse-Doppler is a 4D radar system capable of detecting both target 3D location as well as measuring radial velocity . It uses the Doppler effect to avoid overloading computers and operators as well as to reduce power consumption...
radar
Weather radar
Weather radar, also called weather surveillance radar and Doppler weather radar, is a type of radar used to locate precipitation, calculate its motion, estimate its type . Modern weather radars are mostly pulse-Doppler radars, capable of detecting the motion of rain droplets in addition to the...
data, photogrammetry
Photogrammetry
Photogrammetry is the practice of determining the geometric properties of objects from photographic images. Photogrammetry is as old as modern photography and can be dated to the mid-nineteenth century....
, and ground swirl patterns (cycloidal marks) may also be analyzed to determine intensity and award a rating.
Tornadoes vary in intensity regardless of shape, size, and location, though strong tornadoes are typically larger than weak tornadoes. The association with track length and duration also varies, although longer track tornadoes tend to be stronger. In the case of violent tornadoes, only a small portion of the path is of violent intensity, most of the higher intensity from subvortices
Multiple vortex tornado
A multiple-vortex tornado is a tornado that contains several vortices rotating around, inside of, and as part of the main vortex. These multiple vortices are somewhat similar to eyewall mesovortices found in intense tropical cyclones...
.
In the United States, 80% of tornadoes are EF0 and EF1 (T0 through T3) tornadoes. The rate of occurrence drops off quickly with increasing strength—less than 1% are violent tornadoes(EF4, T8 or stronger).
History of tornado intensity measurements
For many years, before the advent of Doppler radar, scientists had nothing more than educated guesses as to the speed of the winds in a tornado. The only evidence indicating the wind speeds found in the tornado was the damage left behind by tornadoes which struck populated areas. Some believed they reach 400 mph (640 km/h), others thought they might exceed 500 mph (800 km/h), and perhaps even be supersonicSupersonic
Supersonic speed is a rate of travel of an object that exceeds the speed of sound . For objects traveling in dry air of a temperature of 20 °C this speed is approximately 343 m/s, 1,125 ft/s, 768 mph or 1,235 km/h. Speeds greater than five times the speed of sound are often...
. One can still find these incorrect guesses in some old (until 1960s) literature, such as the original Fujita Intensity Scale.
Ted Fujita
was a prominent severe storms researcher. His research at the University of Chicago on severe thunderstorms, tornadoes, hurricanes and typhoons revolutionized knowledge of each.- Biography :Fujita was born in Kitakyūshū, Fukuoka Prefecture, Japan...
introduced the idea for a scale of tornado winds. With the help of colleague Allen Pearson
Allen Pearson
Allen Pearson was the Director of the National Severe Storms Forecast Center from 1965–79 and began to collaborate with Dr. Tetsuya Theodore "Ted" Fujita on tornado physical characteristics soon after the 1970 Lubbock Tornado. They bounced ideas off each other and the Fujita scale and later the...
, he created and introduced what came to be called the Fujita scale
Fujita scale
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...
in 1973. This is what the F stands for in F1, F2, etc. The scale was based on a relationship between the Beaufort scale
Beaufort scale
The Beaufort Scale is an empirical measure that relates wind speed to observed conditions at sea or on land. Its full name is the Beaufort Wind Force Scale.-History:...
and the Mach number
Mach number
Mach number is the speed of an object moving through air, or any other fluid substance, divided by the speed of sound as it is in that substance for its particular physical conditions, including those of temperature and pressure...
scale; the low end of F1 on his scale corresponds to the low end of B12 on the Beaufort scale, and the low end of F12 corresponds to the speed of sound at sea level, or Mach 1. In practice, tornadoes are only assigned categories F0 through F5.
The TORRO scale
TORRO scale
The TORRO tornado intensity scale is a scale measuring tornado intensity between T0 and T11. It was developed by Terence Meaden of the Tornado and Storm Research Organisation , a meteorological organisation in the United Kingdom, as an extension of the Beaufort scale.- History and derivation from...
, created by the Tornado and Storm Research Organisation (TORRO)
Tornado and Storm Research Organisation (TORRO)
The Tornado and Storm Research Organisation was founded by Terence Meaden in 1974. Originally called the Tornado Research Organisation it was expanded in 1982 following the inclusion of the Thunderstorm Census Organisation after the death of its founder Morris Bower and his wife.TORRO comprises...
, was developed in 1974, and published a year later. The TORRO scale has 12 levels, which cover a broader range with tighter graduations. It ranges from a T0 for extremely weak tornadoes to T11 for the most powerful known tornadoes. T0-T1 roughly correspond to F0, T2-T3 to F1, and so on. While T10+ would be approximately an F5, the highest tornado rated to date on the TORRO scale was a T8. There is some debate as to the usefulness of the TORRO scale over the Fujita scale—while it may be helpful for statistical purposes to have more levels of tornado strength, often the damage caused could be created by a large range of winds, rendering it hard to narrow the tornado down to a single TORRO scale category.
Research conducted in the late 1980s and 1990s suggested that, even with the implication of the Fujita scale, tornado winds were notoriously overestimated, especially in significant and violent tornadoes. Because of this, in 2006, the American Meteorological Society
American Meteorological Society
The American Meteorological Society promotes the development and dissemination of information and education on the atmospheric and related oceanic and hydrologic sciences and the advancement of their professional applications. Founded in 1919, the American Meteorological Society has a membership...
introduced the Enhanced Fujita Scale
Enhanced Fujita Scale
The Enhanced Fujita 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:...
, to help assign realistic wind speeds to tornado damage. The scientists specifically designed the scale so that a tornado assessed on the Fujita scale and the Enhanced Fujita scale would receive the same ranking. The EF-scale is more specific in detailing the degrees of damage on different types of structures for a given wind speed. While the F-scale goes from F0 to F12 in theory, the EF-scale is capped at EF5, which is defined as "winds ≥ 200 mph (≥ 320 km/h)". In the United States, the Enhanced Fujita scale went into effect on February 2, 2007 for tornado damage assessments and the Fujita scale is no longer used.
Eight years later, during the 1999 Oklahoma tornado outbreak of May 3, 1999, another scientific team was monitoring an exceptionally violent tornado (one which would eventually kill 36 people in the area near Moore, Oklahoma
Moore, Oklahoma
Moore is a city in Cleveland County, Oklahoma and is part of the Oklahoma City Metropolitan Area. The population was 55,081 at the 2010 census, making it the seventh largest city in the state of Oklahoma....
). At about 7:00 pm, they recorded one measurement of 301±20 mph (484±32 km/h), 50 mi/h faster than the previous record. Though this reading is just short of the theoretical F6 rating, the measurement was taken more than 100 feet (30.5 m) in the air, where winds are typically stronger than at the surface. In rating tornadoes, only surface wind speeds, or the wind speeds indicated by the damage resulting from the tornado, are taken into account. Also, in practice, the F6 rating is not used.
While scientists have long theorized that extremely low pressures might occur in the center of tornadoes, there were no measurements to confirm it. A few home barometer
Barometer
A barometer is a scientific instrument used in meteorology to measure atmospheric pressure. Pressure tendency can forecast short term changes in the weather...
s had survived close passes by tornadoes, recording values as low as 24 in Hg (810 mbar), but these measurements were highly uncertain. However, on June 24, 2003, a group of researchers successfully dropped devices called "turtles" into an F4 tornado near Manchester, South Dakota
Manchester, South Dakota
Manchester was a small unincorporated community in Kingsbury County in the east-central part of the U.S. state of South Dakota. On June 24, 2003, the town was completely annihilated by a large F4-rated tornado, and has since become a ghost town.-History:...
, one of which measured a pressure drop of more than 100 mbar as the tornado passed directly overhead. Still, tornadoes are widely varied, so meteorologists are still conducting research to determine if these values are typical or not.
Typical intensity
In the United States, F0 and F1 (T0 through T3) tornadoes account for 80% of all tornadoes. The rate of occurrence drops off quickly with increasing strength—violent tornadoes (stronger than F4, T8), account for less than 1% of all tornado reports. Worldwide, strong tornadoes account for an even smaller percentage of total tornadoes. Violent tornadoes are extremely rare outside of the United States, Canada and Bangladesh.F5 and EF5 tornadoes are exceptionally rare, occurring on average once every few years. The last confirmed F5 tornado anywhere in the world was the Elie, Manitoba Tornado
Elie, Manitoba Tornado
The Elie, Manitoba Tornado was an F5 tornado that struck the town of Elie, Manitoba, Canada, on June 22, 2007. While several houses were leveled, no one was injured or killed by the tornado. Two well-built homes in the town were swept clean off of their foundations, justifying the F5...
in Canada, on June 22, 2007. Before that, the last confirmed F5 was the Moore, Oklahoma tornado, which killed 36 people on May 3, 1999. Eight EF5 tornadoes have occurred in the United States, in Greensburg, Kansas
Greensburg, Kansas
Greensburg is a city in and the county seat of Kiowa County, Kansas, United States. As of the 2010 census, the city population was 777. Greensburg is also home to the world's largest hand-dug well....
on May 4, 2007; Parkersburg, Iowa
Parkersburg, Iowa
Parkersburg is a city in Butler County, Iowa, United States. The population was 1,870 in the 2010 census, a decline from 1,889 in the 2000 census. Parkersburg, although not the county seat, has the highest population of all the cities in Butler County....
on May 25, 2008; Smithville, Mississippi
Smithville, Mississippi
Smithville is a town in Monroe County, Mississippi, United States. The population was 882 at the 2000 census. Smithville is the birthplace of Rod Brasfield, a member of the Country Music Hall of Fame.-Geography:...
, Philadelphia, Mississippi
Philadelphia, Mississippi
Philadelphia is a city in and the county seat of Neshoba County, Mississippi, United States. The population was 7,303 at the 2000 census.- History :...
, Hackleburg, Alabama
Hackleburg, Alabama
Hackleburg is a town in Marion County, Alabama, United States. At the 2010 census the population was 1,430. It is also the hometown of country music singer Sonny James. James had numerous country and cross over pop hits starting in the 1950s though the 1970s...
and Rainsville, Alabama
Rainsville, Alabama
Rainsville is a city in DeKalb County, Alabama, United States. At the 2000 census the population was 4,499. Rainsville is located on top of Sand Mountain.Rainsville was incorporated in October 1956....
(four separate tornadoes) on April 27, 2011; Joplin, Missouri
Joplin, Missouri
Joplin is a city in southern Jasper County and northern Newton County in the southwestern corner of the US state of Missouri. Joplin is the largest city in Jasper County, though it is not the county seat. As of the 2010 census, the city population was 50,150...
on May 22, 2011 and El Reno, Oklahoma
El Reno, Oklahoma
El Reno is a city in Canadian County, Oklahoma, United States, in the central part of the state. A part of the Oklahoma City Metropolitan Statistical Area, El Reno is west of downtown Oklahoma City...
on May 24, 2011.
Typical damage
| F0 EF0 |
F1 EF1 |
F2 EF2 |
F3 EF3 |
F4 EF4 |
F5 EF5 |
|---|---|---|---|---|---|
| Weak | Strong | Violent | |||
| Significant | |||||
| Intense | |||||
A typical tornado has winds of 110 mph (175 km/h) or less, is approximately 250 feet (75 m) across, and travels a mile (1.6 km) or so before dissipating. However, tornadic behavior is extremely variable; these figures represent only statistical probability.
Two tornadoes that look almost exactly the same can produce drastically different effects. Also, two tornadoes which look very different can produce similar damage. This is due to the fact that tornadoes form by several different mechanisms, and also that they follow a life cycle which causes the same tornado to change in appearance over time. People in the path of a tornado should never attempt to determine its strength as it approaches. Between 1997 and 2005 in the United States, 38 people were killed by EF1 tornadoes, and 3 were killed by EF0 tornadoes. Even the weakest tornado can kill.
- Weak tornadoes
The vast majority of tornadoes are designated EF1 or EF0, also known as "weak" tornadoes. However, weak is a relative term for tornadoes, as even these can cause significant damage. F0 and F1 tornadoes are typically short-lived—since 1980 almost 75% of tornadoes rated weak stayed on the ground for one mile (1.6 km) or less. However, in this time, they can cause both damage and fatalities.
EF0 (T0-T1) damage is characterized by superficial damage to structures and vegetation. Well-built structures are typically unscathed, sometimes sustaining broken windows, with minor damage to roofs and chimney
Chimney
A chimney is a structure for venting hot flue gases or smoke from a boiler, stove, furnace or fireplace to the outside atmosphere. Chimneys are typically vertical, or as near as possible to vertical, to ensure that the gases flow smoothly, drawing air into the combustion in what is known as the...
s. Billboards and large signs can be knocked down. Trees may have large branches broken off, and can be uprooted if they have shallow roots. Any tornado that is confirmed but causes no damage (i.e. remains in open fields) is always rated EF0 as well.
EF1 (T2-T3) damage has caused significantly more fatalities than that caused by EF0 tornadoes. At this level, damage to mobile homes and other temporary structures becomes significant, and cars and other vehicles can be pushed off the road. Permanent structures can suffer major damage to their roofs.
- Significant tornadoes
EF2 (T4-T5) tornadoes are the lower end of "significant", and yet are stronger than most tropical cyclone
Tropical cyclone
A tropical cyclone is a storm system characterized by a large low-pressure center and numerous thunderstorms that produce strong winds and heavy rain. Tropical cyclones strengthen when water evaporated from the ocean is released as the saturated air rises, resulting in condensation of water vapor...
s (though tropical cyclones affect a much larger area and their winds take place for a much longer duration). Well-built structures can suffer serious damage, including roof loss and collapse of outer walls. Mobile homes, however, are almost totally destroyed. Vehicles can be lifted off the ground, and lighter objects can become small missile
Projectile
A projectile is any object projected into space by the exertion of a force. Although a thrown baseball is technically a projectile too, the term more commonly refers to a weapon....
s, causing damage outside of the tornado's main path. Wooded areas will have a large percentage of their trees snapped or uprooted.
EF3 (T6-T7) damage is a serious risk to life and limb and the point at which a tornado statistically becomes significantly more destructive and deadly. Few parts of affected buildings are left standing; well-built structures lose all outer and most inner walls. Small vehicles and similarly sized objects are lifted off the ground and tossed as projectiles. Wooded areas will suffer almost total loss of vegetation. Statistically speaking, EF3 is the maximum level that allows for reasonably effective residential sheltering in place in a first floor interior room, closest to the center of the house (the most widespread tornado sheltering procedure in America for those with no basement). Although reasonably effective against tornadoes EF0-2, EF3+ represents the point at which no home can expect to retain any interior walls to shield the occupants, and thus those sheltering above ground will face a high likelihood of severe injury or death as the structure is ripped apart.
- Violent tornadoes
EF4 (T8-T9) damage typically results in a total loss of the affected structure. Well-built homes are reduced to a short pile of medium-sized debris on the foundation. Large, heavy vehicles, including airplane
Fixed-wing aircraft
A fixed-wing aircraft is an aircraft capable of flight using wings that generate lift due to the vehicle's forward airspeed. Fixed-wing aircraft are distinct from rotary-wing aircraft in which wings rotate about a fixed mast and ornithopters in which lift is generated by flapping wings.A powered...
s, train
Train
A train is a connected series of vehicles for rail transport that move along a track to transport cargo or passengers from one place to another place. The track usually consists of two rails, but might also be a monorail or maglev guideway.Propulsion for the train is provided by a separate...
s, and large truck
Truck
A truck or lorry is a motor vehicle designed to transport cargo. Trucks vary greatly in size, power, and configuration, with the smallest being mechanically similar to an automobile...
s, can be pushed over, flipped repeatedly or picked up and moved short distances. Large, healthy trees are entirely debarked and snapped off close to the ground or uprooted altogether and turned into flying projectiles. Passenger cars and similarly sized objects can be picked up and flung for considerable distances. EF4 damage can be expected to level even the most robustly built homes, making the common practice of sheltering in an interior room on the ground floor of a residence insufficient to ensure survival. A storm shelter, reinforced basement or other subterranean shelter is considered necessary to provide any reasonable expectation of safety against EF4 damage.
EF5 (T10+) damage represents the upper limit of tornado power, and destruction is almost always total. An EF5 tornado pulls well-built homes off their foundations and into the air before shredding them, flinging the wreckage for miles and sweeping the foundation clean. Very little recognizable structural debris is generated by EF5 damage, with most materials reduced to a coarse mix of small, granular particles and dispersed evenly across the tornado's damage path. Large, multi-ton steel frame vehicles and farm equipment are often mangled beyond recognition and deposited miles away or reduced entirely to unrecognizable component parts. The official description of this damage highlights the extreme nature of the destruction, noting that "incredible phenomena will occur"; historically, this has included such awesome displays of power as twisting skyscrapers
Lubbock Tornado
The 1970 Lubbock tornado was a tornado event that occurred in Lubbock, Texas, on May 11, 1970. It was one of the worst tornadoes in Texas history, and occurred exactly 17 years to the day after the deadly Waco Tornado...
, levelling entire communities, and stripping asphalt from roadbeds. Despite their relative rarity, the damage caused by EF5 tornadoes represents a disproportionately extreme hazard to life and limb— since 1950 in the United States, only 58 tornadoes (0.1% of all reports) have been designated F5 or EF5, and yet these have been responsible for more than 1300 deaths and 14,000 injuries (21.5% and 13.6%, respectively).
See also
- TornadoTornadoA tornado is a violent, dangerous, rotating column of air that is in contact with both the surface of the earth and a cumulonimbus cloud or, in rare cases, the base of a cumulus cloud. They are often referred to as a twister or a cyclone, although the word cyclone is used in meteorology in a wider...
- Fujita scaleFujita scaleThe 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...
- Tornado recordsTornado recordsThis article lists various tornado records. The most extreme tornado in recorded history was the Tri-State Tornado, which roared through parts of Missouri, Illinois, and Indiana on March 18, 1925. It was likely an F5, though tornadoes were not ranked on any scale in that era...
- Tornado climatologyTornado climatologyThe United States has the most tornadoes of any country, nearly four times more than estimated in all of Europe, excluding waterspouts. This is mostly due to the unique geography of the continent. North America is a large continent that extends from the tropics north into arctic areas, and has no...
- Super OutbreakSuper OutbreakThe Super Outbreak is the second largest tornado outbreak on record for a single 24-hour period, just behind the tornado outbreak of April 25–28, 2011...