Tornado

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This article is about the weather phenomenon. For other uses, see Tornado (disambiguation).

Union City, Oklahoma tornado (1973)

A tornado is a violently rotating column of air which is in contact with both a cumulonimbus (or, in rare cases, cumulus) cloud base and the surface of the earth. Tornadoes can come in many shapes, but are typically in the form of a visible condensation funnel, with the narrow end touching the earth. Often, a cloud of debris encircles the lower portion of the funnel.

Tornadoes can be the most destructive storms on earth. Most have winds of 112 mph (180 km/h) or less, are approximately 250 feet (75 meters) across, and travel a mile (1.6 km) or more before dissipating. However, some tornadoes can have winds of more than 300 mph (500 km/h), be more than 2 miles (3 km) across, and stay on the ground for dozens of miles (more than 100 kilometers). Williams, Jack. "[Doppler radar measures 318 mph wind in tornado]." USA Today. May 17, 2005."[Hallam Nebraska Tornado]." [National Weather Service Weather Forecast Office, Omaha/Valley, NE]. November 2, 2005. Edwards, Roger. "[The Online Tornado FAQ]." [Storm Prediction Center]. April 4, 2006.

They have been observed on every continent except Antarctica; however, a significant percentage of the world's tornadoes occur in the United States. Perkins, Sid. "[Tornado Alley, USA]." [Science News]. May 11, 2002. This is mostly due to the unique geography of the country, which allows the conditions which breed strong, long-lived storms to occur many times a year. Other areas which often experience tornadoes are south-central Canada, northwestern Europe, east-central South America, South Africa, and south-central Asia. "[Tornado]." [Encyclopædia Britannica]. 2006.

Etymology

Definitions

Stronger tornadoes are often observed to have multiple vortices, or many columns of violently spinning air rotating around a common center. However, a satellite tornado is a term for a weak tornado which forms very near a large, strong tornado, often lasting no more than a minute. The satellite tornado may appear to "orbit" the larger tornado (hence the name), giving the appearance of one, large multi-vortex tornado. However, a satellite tornado is a distinct funnel, and is much smaller than the main funnel.

A waterspout is a tornado over water. In general, most tornadoes over land are associated with a severe thunderstorm; however, the National Weather Service in the United States considers all waterspouts—including "fair weather" waterspouts—to be tornadoes. These less severe relatives of classic tornadoes are almost always very weak (F0 on the Fujita Scale), and spawn from non-rotating thunderstorms, or even regular summer showers. Typically, waterspouts moving onto land cause little or no damage, and dissipate within minutes. However, strong waterspouts from supercells can cause significant damage if they impact land areas. In addition, strong tornadoes can move over lakes or over the ocean, becoming waterspouts, without losing intensity.

A landspout is an unofficial term for a tornado not associated with a mesocyclone. Known officially as a dust-tube tornado, it is usually weak, features a small condensation funnel which often does not appear to reach the ground, and is often marked by a tall tube of dust and/or debris reaching as far up as the parent cloud. Though usually weaker than ordinary tornadoes, they are tornadoes, and can cause serious damage.

A gustnado is a small, vertical swirl associated with a gust front or downburst. Because they are technically not associated with the cloud base, there is some debate as to whether or not gustnadoes are actually tornadoes. "[AMS Glossary of Meteorology]." [American Meteorological Society]. June, 2000. These usually cause localized areas of heavier damage among areas of straight-line wind damage caused by the gust front.

A sequence of images showing the birth of a tornado. First, the rotating cloud base lowers. This lowering becomes a funnel, which continues descending while winds build near the surface, kicking up dust and other debris. Finally, the visible funnel extends to the ground, and the tornado begins causing major damage.

Life Cycle

Most tornadoes follow a recognizable life cycle. The cycle begins when a strong thunderstorm develops a rotating mesocyclone a few miles up in the atmosphere, becoming a supercell. As rainfall in the storm increases, it drags with it an area of quickly descending air known as the rear flank downdraft (RFD). This downdraft accelerates as it approaches the ground, and drags the rotating mesocyclone towards the ground with it.

As the mesocyclone approaches the ground, a visible condensation funnel appears to descend from the base of the storm, often from a rotating wall cloud. As the funnel decends, the RFD also reaches the ground, creating a gust front that can cause damage a good distance from the tornado. Usually, the funnel cloud begins causing damage on the ground (becoming a tornado) within minutes of the RFD reaching the ground.

Initially, the tornado has a good source of warm, moist inflow to power it, so it grows until it reaches the mature stage. During its mature stage, which can last anywhere from a few minutes to more than an hour, a tornado often causes the most damage, and can in rare instances be more than one mile across. Meanwhile, the RFD, now an area of cool surface winds, begins to wrap around the tornado, cutting off the inflow of warm air which feeds the tornado.

As the RFD completely wraps around and chokes off the tornado's air supply, the tornado begins to weaken, becoming thin and rope-like. This is the dissipating stage, and the tornado often fizzles within minutes. During the dissipating stage, the shape of the tornado becomes highly influenced by the direction of surface winds, and can be blown into fantastic patterns.

As the tornado enters the dissipating stage, its associated mesocyclone often weakens as well, as the rear flank downdraft cuts off the inflow powering it. In particularly intense supercells, tornadoes can develop [cyclically]. As the first mesocyclone and associated tornado dissipate, the storm's inflow is concentrated into a new area closer to the center of the storm. If a new mesocyclone develops, the cycle may start again, producing a new tornado. Occasionally, the old, or occluded mesocyclone, and the new mesocyclone produce a tornado at the same time.

Though this is a widely-accepted theory for how most tornadoes form, live, and die, it does not explain the formation of smaller tornadoes, such as landspouts, long-lived tornadoes, or tornadoes with multiple vorticies. These each have different mechanisms which influence their development—however, most tornadoes follow a pattern similar to this one.

Characteristics

A wedge tornado, nearly a mile wide.

A rope tornado in its dissipating stage. The horizontal lines in the foreground are power cables.

A multiple-vortex tornado outside of Dallas, Texas on April 2, 1957.

Shape

Small, relatively weak landspouts might only be visible as a small swirl of dust on the ground. While the condensation funnel may not extend all the way to the ground, if winds at the surface are greater than 40 mph (64 km/h), it is considered a tornado.

Large single-vortex twisters, often violent, can look like a large wedge stuck into the ground, and are known as wedge tornadoes or wedges. Wedges can be so wide that they appear to be a block of dark clouds. Even experienced storm observers may not be able to tell the difference between a low-hanging cloud and a wedge tornado from a distance.

Tornadoes in the dissipating stage can appear like narrow tubes, or ropes, twisting into all manner of curls, twists, and s-shapes. A tornado such as this is roping out, or becoming a rope tornado.

Multiple-vortex tornadoes can appear as a family of swirls circling a common center, or may be completely obscured by debris, appearing to be a single funnel.

In addition to these appearances, tornadoes may be obscured completely by rain or dust. These tornadoes are especially dangerous, as even experienced meteorologists might not spot them. Lyons, Walter A. The Handy Weather Answer Book. Detroit, MI: Visible Ink Press, 1997.

Size

Weak tornadoes, or strong but dissipating tornadoes, can be exceedingly narrow, sometimes only a few feet across. In fact, a tornado was once reported to have a damage path only 7 feet (2.1 m) long.

On the other end of the spectrum, a tornado which affected Hallam, Nebraska on May 22, 2004 was at one point 2.5 miles (4 km) wide"[Hallam Nebraska Tornado]." [National Weather Service Weather Forecast Office, Omaha/Valley, NE]. November 2, 2005.. In terms of path length, some meteorologists believe that the Tri-State Tornado, which affected parts of Missouri, Illinois, and Indiana on March 18, 1925, was on the ground continuously for 219 miles (352 km). However, without a modern damage survey, it is impossible to determine whether or not the deadly event was a single tornado or a series of violent tornadoes produced by the same storm. The longest modern-day tornado track was a tornado which was on the ground for 160 miles (257 km) in northeastern North Carolina on November 22, 1992.

Appearance

These are two photographs of the Waurika, Oklahoma tornado of May 30, 1976, taken at nearly the same time. In the top picture, the tornado is front-lit, with the sun behind the east-facing camera, so the funnel appears nearly white. In the lower image, where the camera is facing the opposite direction, the tornado is back-lit, with the sun behind the clouds. Edwards, Roger. "[Public Domain Tornado Images]." [Storm Prediction Center].

Lighting conditions are also a major factor in the appearance of a tornado. A tornado which is "back-lit", or viewed with the sun behind it, will appear to be very dark. The same tornado, viewed with the sun at the observer's back, may appear grey or brilliant white. Tornadoes which occur near the time of sunset can be many different colors, appearing in hues of yellow, orange, and pink.

Dust kicked up by the winds of the parent thunderstorm, heavy rain and hail, and the darkness of night are all factors which can reduce the visibility of tornadoes, making them "invisible", in essence. Tornadoes occurring in these conditions are especially dangerous, since only radar observations, or possibly the sound of an approaching tornado, serve as any warning to those in the storm's path. Fortunately most significant tornadoes form under the storm's rain-free base, or the area under the thunderstorm's updraft, where there is little or no rain. In addition, most tornadoes occur between the hours of 4 and 8 pm, when the bright sun can penetrate even the thickest clouds. Also, night-time tornadoes are often illuminated by frequent lightning.

There is mounting evidence, including doppler radar images Monastersky, R. "[Oklahoma Tornado Sets Wind Record]." [Science News]. May 15, 1999 and eyewitness accounts Justice, Alonzo A. "[Seeing the Inside of a Tornado]." Monthly Weather Review. May, 1930., which suggest that most tornadoes have a clear, calm center with extremely low pressure, akin to the eye found in tropical cyclones. This area would be clear (possibly full of dust), have relatively light winds, and be very dark, with the light blocked out by swirling debris on the outside of the tornado. Lightning is said to be the source of illumination for those who claim to have seen the interior of a tornado.

Rotation

Intensity and damage

For many years, before the advent of home movies and 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 thought they might exceed 500 mph, and perhaps even be supersonic.

In the 1950's however, evidence mounted that the actual wind speeds were much lower than this. On April 2, 1957, a slow moving tornado traversed the south and east parts of Dallas, Texas. Before this day, only a few photographs and motion pictures of tornadoes were known to exist. However, because of many factors, including the tornado's high visibility, slow forward motion, and proximity to an urban center, it became (and still may be) the most filmed and photographed tornado in history. Frame-by-frame analysis of several pieces of footage taken that day showed that the debris flung about by the tornado was travelling at speeds up to 170 mph.VIDEO Lloyd, Linda Mercer. Target: Tornado. [The Weather Channel Enterprises, Inc.] 1996.

Major damage to homes in Stoughton, Wisconsin caused by an F3 tornado on August 18, 2005.

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. 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, developed 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.Meaden, Dr. Terence. "[A Brief History of TORRO (to 1985)]." [The Tornado and Storm Research Organisation]. 1985.

There is some debate as to the usefulness of the TORRO scale over the Fujita scale—while it is helpful for statistical purposes to have more levels of tornado strength, often the damage caused could be created by a large range of winds, so it is nearly impossible to narrow the tornado down to a single TORRO scale category. Worldwide, the preferred scale for measuring the intensity of a tornado is the Fujita scale. The United Kingdom and some other areas of Europe use the TORRO scale. The ranking of a tornado on either scale is determined by Doppler radar wind speed data (if available), videogrammetry (frame-by-frame analysis of video footage), and empirical data derived from damage to structures and vegitation.

In the United States, F0 and F1 (T0 through T3) tornadoes account for 80% of all tornadoes. On the other hand, violent tornadoes (stronger than F4, T8), account for less than 1%. Edwards, Moller, Purpura et al. "[Basic Spotters' Field Guide]." [US Department of Commerce], [National Weather Service]. 2005. Worldwide, strong tornadoes account for an even smaller percentage of total tornadoes. Violent tornadoes are extremely rare outside of the United States.

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 will be used for tornado damage assessments beginning February 2, 2007.

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 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 pm, they recorded one measurement of 318 mph , 50 mph faster than the previous record. Though this reading is just short of the theoretical F6 rating, the measurement was taken more than 100 feet in the air, where winds are typically stronger than at the surface.

Prediction and detection

Probabilistic maps issued by the Storm Prediction Center during the heart of the April 6-8, 2006 Tornado Outbreak. The top map indicates the risk of general severe weather (including large hail, damaging winds, and tornadoes), while the bottom map specifically shows the percent risk of a tornado forming within 25 miles (40 km) of any point within the enclosed area. The hashed area on the bottom map indicates a 10% or greater risk of an F2 or stronger tornado forming within 25 miles (40 km) of a point.

United States

Warnings are issued by the regional National Weather Service offices, while Watches are issued directly from the SPC.

The National Weather Service trains Skywarn spotters, consisting of local sheriff's deputies, state troopers, and ordinary citizens, to spot key features of storms which indicate severe hail, strong winds, and tornadoes. When severe weather is anticipated, local weather service offices request that these spotters be on the lookout for severe weather, and report any possible tornadoes immediately, so the office can issue a timely warning.

United Kingdom

Climatology

Frequency of occurrence

The United States experiences by far the most tornadoes of any country, and has also suffered the most intense ones. Tornadoes are common in several states, particularly in the Midwest. There is a secondary peak in autumn, especially in the southeastern U.S. where winter tornadoes are more frequent than in other areas.

The time of year is a big factor of the intensity and frequency of tornadoes in the United States. On average, in the United States as a whole, the month with the most tornadoes is May, followed by the months June, April, and July. On average, there are around 294 tornadoes nationwide during the month of May, and as much as 543 tornadoes have been reported in the month of May alone ( in 2003 ). The months with the fewest tornadoes are usually December and January, although major tornado outbreaks can basically occur any time of year. In general, in the Midwestern and Plains states, springtime ( especially the month of May ) is the most active season for tornadoes, while in the far northern states ( like Minnesota and Wisconsin ), the peak tornado season is usually in the summer months ( June, July, and August ) In the colder autumn and winter months, tornado activity is generally limited to the south, where it is possible for warm Gulf of Mexico air to penetrate.

The reason for the peak of tornado season in the spring has much to do with temperature patterns in the U.S. Tornadoes often form when cool, polar air travelling southeastward from the rockies overrides warm, moist, unstable Gulf of Mexico air in the eastern states. Tornadoes therefore tend to be commonly found in front of a cold front, along with heavy rains, hail, and damaging winds. Since both warm and cold weather are common during the springtime, the conflict between these two air masses tends to be most common in the spring. As the weather warms across the country, the occurrence of tornadoes spreads northward. Tornadoes are also common in the summer because they can also be triggered by hurricanes, although the tornadoes caused by hurricanes are often much weaker and harder to spot. Winter is the least common time for tornadoes to occur, since hurricane activity is virtually non - existent at this time, and it is more difficult for warm, moist maritime tropical air to take over the frigid arctic air from Canada. Interestingly, there is a second active tornado season of the year - sometime around late October/early November. Autumn, like spring, is a time of the year when warm weather alternates with cold weather frequently, especially in the midwest, but the season is not as active as it is during the springtime.

Some people mistakenly believe that tornadoes only occur out in the countryside. This is hardly the case. While it is true that the plains states are the most tornado - prone places in the nation, it should be noted that tornadoes have been reported in every U.S state, including Alaska and Hawaii. One likely reason why tornadoes are so common in the central U.S is because this is where arctic air first collides with warm tropical air from the Gulf of Mexico where the cold front has not been "weakened" yet. As it heads further east, however, it is possible for the front to lose its strength as it travels over more warm air. Therefore, tornadoes are not as common on the east coast as they are in the midwest.

Tornadoes can occur in the West as well, although they are usually small and relatively weak. Recently tornadoes have struck the Pacific coast town of Lincoln City, Oregon (1996), and downtown Salt Lake City, Utah (1999) (see Salt Lake City Tornado). The California Central Valley is an area of some frequency for tornados, albeit of weak intensity. More tornadoes occur in Texas than in any other US state. The state which has the highest number of tornadoes per unit area is Florida, although most of the tornadoes in Florida are weak tornadoes of F0 or F1 intensity. A number of Florida's tornadoes occur along the edge of hurricanes that strike the state. The state with the highest number of strong tornadoes per unit area is Oklahoma. The neighboring state of Kansas is another particularly notorious tornado state. It should be mentioned that states such as Oklahoma and Kansas have much lower population densities than Florida and that tornadoes may go unreported.

On average, the United States experiences 100,000 thunderstorms each year, resulting in more than 1,200 tornadoes and approximately 50 deaths per year. The deadliest U.S. tornado recorded is the March 18, 1925, Tri-State Tornado that swept across southeastern Missouri, southern Illinois and southern Indiana, killing 695 people. The biggest tornado outbreak on record—with 148 tornadoes, including six F5 and 24 F4 tornadoes—occurred on April 3, 1974. It is dubbed the Super Outbreak. Another such significant storm system was the Palm Sunday Tornado Outbreak, which affected the United States Midwest on April 11, 1965. A series of continuous tornado outbreaks is known as a tornado outbreak sequence, with significant occurrences in May 1917, 1930, 1949, and 2003.

Canada also experiences numerous tornadoes, although fewer than the United States. In Canada, at least 80 tornadoes occur annually (with many more likely undetected in large unpopulated areas), causing tens of millions of dollars in damage. The last tornado-related deaths in Canada was caused by a tornado in Pine Lake, Alberta, on July 14, 2000, where 12 died. The two worst tornados in terms of death toll on Canadian soil were the Edmonton Tornado of July 31, 1987, which measured F4, and the misnamed Regina Cyclone of June 30, 1912, which was likely an F4 or weak F5 tornado.

Tornadoes do occur throughout the world as well; the most tornado-prone region of the world (outside North America), as measured by number of reported tornadoes per unit area, is the Netherlands, followed by the United Kingdom (especially England). Bangladesh, India, Argentina, Italy, Australia, New Zealand, Germany, Estonia, and portions of Uruguay also have pockets of high tornadic activity. Occasional strong tornadoes occur in Russia, France, Spain, Japan, and portions of Paraguay and Brazil. Tornadoes have recently hit South Africa and parts of Pakistan in 2001 as well, and on April 4 2006, a rare F2 tornado hit northwestern Israel, causing significant damage and injuries. Approximately 170 tornadoes are reported per year on land in Europe. One notable tornado of recent years was the tornado which struck Birmingham, United Kingdom, in July 2005. A row of houses was destroyed, but no one was killed. A strong F3 (T7) Tornado hit the small town Micheln in Saxony-Anhalt, Germany on July 23 2004 leaving 6 people injured and more than 250 buildings massively damaged. ^{[[Citing sourcescitations needed]]}

Continuing research

Social implications of tornadoes

Salt Lake City Tornado, August 11, 1999. (Orange fireball is substation exploding)

Tornado damage to man-made structures is a result of the high wind velocity and windblown debris. Tornadic winds have been measured in excess of 300 mph (480 km/h). Tornado season in North America is generally March through November, although tornadoes can occur at any time of year. They tend to occur in the afternoons and evenings; over 80% of all tornadoes strike between noon and midnight.

Some individuals and hobbyists, known as storm chasers, enjoy pursuing thunderstorms and tornadoes to explore their many visual and scientific aspects. Attempts have been made by some storm chasers from educational and scientific institutions to drop probes in the path of oncoming tornadoes in an effort to analyze the interior of the storms, but only about five drops have been successful since around 1990.

Due to the relative rarity and large scale of destructive power that tornadoes possess, their occurrence or the possibility that they may occur can often create what could be considered sensationalism in their reporting. This results in so-called weather wars, in which competing local media outlets, particularly TV news stations, engage in continually escalating technological one-upsmanship and drama in order to increase their market share. This is especially evident in tornado-prone markets, such as those in the Great Plains.

According to Environment Canada, the chances of being killed by a tornado are 12 million to 1 (12,000,000:1). One may revise this yearly and/or regionally, but the probability may be factually stated to be low. Tornadoes do cause millions of dollars in damage, both economic and physical, displacement, and many injuries every year.

Some common misconceptions regarding tornadoes which people should not rely upon to protect them are given in the article on The Super Outbreak of 1974, in which some of the most dangerous tornadoes formed near rivers and crossed them, and crossed over steep hills, mountains and deep valleys. Other misconceptions and science fiction, concerning tornado formation can be found at the article for tornado myths.

Cultural significance

Tornadoes as a metaphor

Cyclone as metaphor for political revolution; the Aunt-Em-type farm woman is labeled 'Democratic Party' and wears exactly the same dress as Dorothy in The Wizard of Oz; Puck magazine (1894)

The tornado has been used by cartoonists for over 100 years as a metaphor for political upheaval. For example, according to political interpretations of The Wizard of Oz, the tornado takes Dorothy to a utopia, the Land of Oz, and kills the Wicked Witch of the East, who had oppressed a little people, the Munchkins. The storm cellar has also been used as a metaphor for seeking safety, as shown in the cartoon from 1894 at right.

A 1960s advertising campaign for the household cleaner, Ajax, claimed the product "Cleans like a white tornado".

Tornadoes in dreams are sometimes said to be associated with fear, chaos, and upheaval. It is alleged that the location where one is during a tornado dream, e.g. at home, can help to determine the meaning.

Motion pictures with a tornado theme

• The Wizard of Oz, 1939.
• Mr. and Mrs. Bridge, 1990.
• [Night of the Twisters (TV)], 1996.
• [Tornado! (TV)], 1996.
• Twister, 1996.
• Atomic Twister (TV), 2001.
• The Day After Tomorrow, 2004.
• [[Perfect Disaster: Super Tornado (Discovery Channel)]], premiered on March 19, 2006.
• [[Category 7: The End of the World]], 2005.

See also

• Cyclone
• Derecho
• Downburst
• Emergency Alert System
• Firewhirl
• Funnel cloud
• Gustnado
• History of tropical cyclone-spawned tornadoes
• Landspout
• List of F5 tornadoes
• List of tornadoes and tornado outbreaks
• List of tornado-related deaths at schools
• Mesocyclone
• Multiple vortex tornado
• NLM Cityhopper Flight 431
• Severe weather
• Supercell
• Tornado Alley
• Tornado records
• Tornadoes of 2006
• Waterspout

References

Further reading

• Thomas P. Grazulis (1993). Significant Tornadoes 1680-1991, A Chronology and Analysis of Events. The Tornado Project of Environmental Films. ISBN 1879362007

External links

General

• [Real Time Reports overlaid on Google Maps.]
• [US Tornadoes, Year to date reports.]
• [Tornado research and education] (National Severe Storms Laboratory)
• [WW2010: Tornadoes]
• [The Tornado Project]
• [The Tornado and Storm Research Organisation]
• [European Severe Storms Laboratory]
• [TorDACH: Centre of Competence for Severe Local Storms in D, A, CH]
• [U.S. Severe Weather and Meteorology and Climatology] (University of Nebraska at Lincoln)
• [Tornado Forecasting] (Rasmussen et Markowski)
• [Electronic Journal of Severe Storms Meteorology]
• [NWS Jet Stream Online Weather School]
• [Birth of a Tornado] ~ Animation from MSNBC Interactive
• [Tornado Newspaper Articles Archive] Free archive of more than 50,000 newspaper articles detailing tornadoes through out history.

• [NOAA Tornado Preparedness Guide]
• [Tornado Safety] (The Tornado Project)
• [Tornado Preparedness Tips for School Administrators] (NOAA / SPC)
• [Highway Overpasses as Tornado Shelters: Fallout from the May 3, 1999 Tornado Outbreak] (National Weather Service, Norman, Oklahoma)
• [Natural Disasters - Tornado] Great research site for kids
• [FEMA for Kids: Tornado]

• [Tornadoes in Kansas] Library of Congress, America's Story
• [Tornado damage] (in 1899; archived panoramic photographs)
• [Chasing Tornadoes] (National Geographic Magazine)
• [Stormtrack magazine]
• [StormWiki]
• [Storm Report Map] (Map and Track Tornadoes, Hail and Wind Reports)
• [person carried by tornado survives.]

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