Tornado myths

Tornadoes are a source of persistent urban legends and common misconceptions. Such ideas often deal with the issues of tornado safety, the minimization of tornado damage, and misconceptions about the size, shape, power, path, and other potentials of the tornado itself.

Safety myths

Myth: Highway overpasses are adequate shelter from a tornado.

Those seeking shelter under highway overpasses can actually be subject to more dangers than those not under an overpass. Debris from around the overpass can be blown through, creating a much higher density of dangerous windblown objects. Additionally, stronger winds in the tunnel can potentially suck victims into the tornado itself.

Sensational footage taken by a television crew hiding from a tornado under an overpass during the 1991 Andover, Kansas Tornado Outbreak helped fuel the myth that the underside of bridges or overpasses are good shelters when a tornado is nearby. The members of the television crew (and several other travelers) survived the tornado while huddling underneath an overpass and bracing themselves against support columns while a tornado appeared to pass directly overhead. However, the tornado did not pass directly over the filmed bridge, but instead tracked slightly south of the area, therefore exposing the people in the footage to winds much less damaging than those possible from a direct hit from the tornado. The overpass was designed with a hollow crawlspace at the top of the embankment, and was large enough to allow people to crawl inside and hold the exposed girders against the wind, even though the speed of the wind itself was increased by the tunnel. The design also allowed for added protection against debris. These qualities represent relatively uncommon designs, as many overpasses are completely exposed underneath and lack both exposed girders and construction that provides sufficient protection from debris.

The danger was additionally highlighted during the 1999 Oklahoma tornado outbreak, when 3 deaths and several severe injuries were caused when an F4 tornado crossed two overpasses being used as shelters. One individual left her well-built home and drove several miles to seek shelter under an overpass, in the mistaken belief that she was safer there than inside of her house. All of the individuals received massive injuries from tornadic debris, and several were swept into the tornado itself.

Myth: During a tornado, the southwest corner of a building is the safest.

This myth likely comes from another myth: that tornadoes move in a northeasterly direction. The thought in this particular myth is that staying in the southwest corner of the house leads to a decrease in the harm potential of a house's debris, since the tornado will spend more time carrying debris from a home away from the individuals inside of the home. After the increase in tornado research during the turn of the millennium, the U.S. National Weather Service has now adopted the advice that the central-most-room on the lowest level of a structure is the safest, with centrally-located rooms in an underground level being far safer than any above-ground location.

Myth: When a tornado approaches your home, the best thing to do is to get in a car and drive away

The official directive from the National Weather Service is for house-dwellers in the path of a tornado to take shelter at home rather than risk an escape by vehicle. This is a result of several factors and statistics. An interior room inside of a well-built frame house (especially one with a basement) provides a reasonable degree of protection from tornadoes rated EF0-EF2, which describe approximately 85% of all tornadoes. This means that in an average tornadic scenario, even a direct hit - while highly damaging to the walls and roof, especially when trees fall - is unlikely to damage a house enough to present a significant risk to the lives of individuals in the safest available room.

By comparison, a vehicle encountering all but the weakest tornadoes would immediately have the windows shattered (subjecting the occupant to lethal flying debris), and would likely be flipped by the ground-level winds. With stronger tornadoes, the vehicle could also be lifted and thrown a considerable distance . Since most individuals are untrained at visually identifying subtle severe weather phenomena, they stand a higher chance of accidentally driving into additional severe weather (including tornadoes) while blindly trying to escape. Even trained spotters and chasers are in danger in a vehicle during a tornado, as a satellite tornado may strike while they are viewing the main tornado.

Flash flooding, torrential rain, severe thunderstorms, hail, and debris on the roadway could easily cause nearly impassable driving conditions, which, when coupled with driver panic, may result in a dangerous (but preventable) accident. The disorganized peril of such a situation would be magnified greatly if all the residents of a warned area left in their vehicles, as this would potentially cause traffic jams and accidents as the tornado approached. Numerous victims of the deadly Wichita Falls, Texas tornado on April 10, 1979 died in their vehicles in such a situation.

If a person spots a nearby tornado while driving, the official National Weather Service directive has always been for the individual to abandon the car and seek shelter in a ditch or culvert. The colloquial opinion among spotters and chasers is that a tornado encountered while driving can be successfully fled from at right angles (90-degree) from its direction of apparent movement. If an encounter is too sudden to flee from, the advice is still to shelter in the ditch rather than the car.

Facts about tornado safety: When in view of a tornado or in a tornado warning, one should seek shelter immediately and calmly if outside or in a mobile home or vehicle, and should avoid wide rooms and rooms containing many windows. The best places are smaller rooms, such as closets or bathrooms. Bathrooms are considered particularly safe since the plumbing fixtures strengthen the walls and anchor them to the ground, while a bathtub can provide some degree of protection from flying debris (a mattress is often placed overhead to further aid in shielding from debris). The void space underneath a stairwell is also a recommended shelter, as the stairway itself braces and strengthens the walls. This particularly works in apartment complexes. Business structures such as walk-in vaults and freezers, small interior offices, and supply closets provide additional protection should a tornado hit while one is in those locations instead of at home.

Despite dangers inherent with operating a vehicle during a tornado, given sufficient advanced warning, mobile home residents have been instructed by the National Weather Service to drive to the nearest secure shelter during a warning.

Tornado behavior

This section will focus on myths regarding the behavior of tornadoes, including their damage paths and shapes.

Myth: Tornadoes sometimes "skip houses".

It is true that a house that is in between two destroyed homes can be "untouched", but this is not the result of a tornado "skipping" as was previously thought. After the Super Outbreak, Dr. Fujita studied many films of tornadoes from that day. Included in his review was damage and tornado film footage of F4 and F5 tornadoes. Fujita concluded that multiple vortices, highly volatile tornadic satellites which orbit the parent tornado at high speeds, are responsible for making tornadoes appear to "skip houses".

Dr. Fujita observed that the main funnel of a multiple-vortex tornadic system moves along a straight path, and the damage radius will miss those structures which are close but not directly inside of the circulation. However, a tornado possessing multiple vortices or satellite tornadoes (smaller but fully formed tornadoes which orbit near the parent tornado much more slowly than do multiple vortices) may damage houses lying outside of the ground circulation caused by the main tornado. Since such an occurrence is not linear, but rather circular and inconsistent, the "house skipping" effect is observed.

Weaker tornadoes, and at times even stronger tornadoes, can occasionally "lift", meaning their circulation has ceased to affect the ground. The result is an erratic and discontinuous linear damage path; however, these discontinuities tend to occur over areas larger than the small neighborhoods where the "house-skipping" effect is observed, except possibly at the time of the birth and organization of the tornado.

Myth: Bigger wedge tornadoes are more powerful than smaller rope tornadoes

This lethal myth portrays the common misconception that tornadoes possessing a wedge structure and a larger damage path are stronger than tornadoes with a thin rope structure or shorter damage path. Regardless of damage strength, tornadoes may change shape at any time; additionally, since all tornadoes are potentially damaging and should be considered a dangerous and immediate threat, one should execute tornado safety procedures no matter what shape the tornado takes.

Should a tornado assume a "rope" appearance from a previously larger shape, the circulation increases due to the conservation of angular momentum. Therefore, the wind velocities of a tornado assuming a rope structure from a wider structure could potentially increase (provided that the parameters producing the tornado have not themselves weakened). Spotters and chasers often mention that a longer-lived tornado is roping out during its final stages, and typically assume that the tornado will soon dissipate; however, the tornado is still very destructive for reasons mentioned above.

Smaller-structured tornadoes and wedge tornadoes both have been labeled from the weakest to the highest rating. Since even a weak, sporadic tornado with a narrow damage path could strengthen at any time, any report of a tornado of any shape should convince an individual in the path of the storm to seek shelter immediately.

Myth: A tornado that doesn't look like it is on the ground is not on the ground.

This is another deadly myth. A tornado appears to be on the ground only when its condensation funnel descends to the surface, but this is untrue. The circular, violent surface winds, and not the condensation funnel, is what both defines the tornado and causes the tornado's damage. Spotters should keep sight of swirling debris directly under any visible funnel or rotating wall cloud, even if such structures appear to not descend entirely to the ground.

Additionally, tornadoes can be wrapped in rain, and thus may not be immediately visible at all.

Myth: A tornado always moves to the northeast.

This is false, and a potentially deadly myth which can lead to a false sense of security, especially for unaware spotters or chasers. Although the majority of tornadoes move northeast, tornadoes can arrive from any direction. A strong tornado that hit the city of Jarrell, Texas in 1997 moved to the southwest - directly opposite of commonly expected storm motion. Additionally, tornadoes can shift without notice due to storm motion changes or effects on the tornado itself from factors such as its rear flank downdraft.

Structure safety and preservation

Myth: Most tornado damage is due to the low pressure in the tornado causing the house to explode. Opening one's windows or doors while a tornado approaches will equalize atmospheric pressure and help prevent property damage.

Since windows are typically the most fragile external feature of a house, they are in more danger from flying debris. Opening them during an active tornado wastes time and effort that could be spent on other, more useful protective measures. A common tornado witticism states "Don't bother opening your windows; the tornado will do that for you." Homes do not "explode" when hit by a tornado, though it often appears so. Commonly, a tornado will break the windows first, allowing strong winds to enter the home. These winds may then push on the underside of the roof upwards, blowing it off. Without the roof, the walls lose structural support and will often fall outwards. Observing the wreckage after the collapse may give the impression the house was pushed apart from the inside.

Studies from the National Hurricane Center suggest that closed containers do not explode during high wind scenarios. However, an opening such as a broken window will allow hurricane- or tornado-force winds to enter a room and subsequently destroy an entire building.

Myth: Twisters are attracted to mobile homes and/or trailer parks.

Trailer parks consist of low-cost mobile homes with less structural integrity than traditional houses. A weak storm that leaves little damage to well-built structures might devastate a trailer park. Mobile homes do not attract tornadoes; they are just more susceptible to damage from them. While the popular assumption is that trailer parks are "tornado magnets", they are no more likely to be hit than a selected field, farm house, or town than anything else in a tornado-prone area. Additionally, trailer parks are often scattered over the outskirts of urban areas, and take a significant percentage of occupied land, therefore providing a relatively high opportunity for an urban tornado to strike them.

Tornadoes and terrain

This section explores myths concerning the effect of certain terrain on tornado behavior.

Myth: Tornadoes cannot form near rivers or cross them, nor do they strike areas near the confluence of two major rivers.

Myth: Tornadoes cannot follow terrain into steep valleys.

Myth: Tornadoes cannot travel over steep hills or mountains.

During the Super Outbreak, a tornado formed near Sayler Park section of Cincinnati, Ohio (near the Ohio River). It was among the six F5s of the outbreak. The city of Cairo, Illinois, which lies at the confluence of the Ohio and Mississippi Rivers, was also hit by a tornado that day.

The Tri-State Tornado of 1925 crossed the Mississippi river and the Wabash river, and possibly several other small bodies of water.

The F5 tornado of May 3, 1999 crossed the Canadian River in Oklahoma before it hit Moore, Oklahoma.

The Windsor - Tecumseh, Ontario Tornado of 1946 crossed the Detroit River from River Rouge, Michigan into downtown Windsor, Ontario, where the river is roughly 3/4 of a mile wide. The F3 tornado that struck on July 2, 1997 also crossed the river into Windsor.

During the Super Outbreak, after destroying three schools, the Monticello tornado crossed over a 60-foot bluff and the Tippecanoe River and damaged several homes.

During the Super Outbreak, the Huntsville tornado crossed Monte Sano mountain (1,650 feet) and gained in intensity as it descended the mountain.

During the same outbreak, an F4 tornado caused damage in Murphy, NC after crossing a 3,000-foot ridge, and F2 tornadoes were confirmed in Roanoke, VA and Great Smoky Mountains National Park, NC. Tornadoes formed elsewhere in West Virginia, western Virginia, southwestern North Carolina, and north Georgia - regions of four states that are in the ranges of the Appalachian mountains.

Appalachia has been struck by other destructive tornado outbreaks: during the "Enigma" outbreak (Feb. 19, 1884), at least one major tornado family struck the mountains of Southwestern North Carolina. On May 1, 1929, a destructive tornado outbreak swept from SW to NE up the Appalachians from Alabama to Maryland, spawning destructive tornadoes at Rye Cove, VA, Morgantown, WV, and in a series moving from Rappahannock County, VA to Frederick, MD. In 1944, a devastating tornado outbreak swept from NW to SE through parts of Ohio, West Virginia, Pennsylvania, Maryland and Virginia, with the worst damage seen in mountainous areas between Pittsburgh and Washington, DC. And in May 1985, several large tornadoes associated with a wide outbreak crossed the Alleghenies in central Pennsylvania.

High altitudes are not necessarily an impediment to tornado formation - the 1999 Salt Lake City Tornado in Utah formed at elevations of over 4000 feet and produced F2 damage in the downtown area. Farther north, a 1989 tornado shredded timber and left a mile-wide path of F4 damage over extremely rugged terrain in the Teton Wilderness in Wyoming, crossing the continental divide at an elevation of over 11,000 feet. In 2004, a tornado was photographed near Rockwell Pass in the Sierra Nevada of California at nearly 12,000 feet. However, it should be noted (for other climatological reasons) that it is a rare occurrence for tornadoes to form west of the Rocky Mountains.

Myth: Downtowns are safe from tornadoes.

It is commonly believed that a tornado will dissipate in an urban area because of tall skyscrapers. The tornado that ripped through the heart of downtown Fort Worth, Texas in March of 2000 negates this belief. Even more evidence comes from the March 14, 2008 tornado which struck downtown Atlanta, which blew out the windows of several skyscrapers and partially peeled the roof away from the Georgia Dome, Georgia World Congress Center and CNN Center.

Tornadoes can even strike large urban areas in the Northeastern United States. On August 8, 2007 an EF2 tornado touched down on three separate occasions in Brooklyn, New York, blowing roofs off apartments and uprooting large trees. The 2007 Brooklyn tornado and its associated storm severely disrupted the morning commute in New York City, and particularly affected the subway system.

It should be noted that city downtowns typically form a small percentage of area relative to both non-urban areas and their surrounding urban and suburban areas; thus, statistics dictates that such smaller areas will necessarily receive less tornado potential than comparatively larger areas such as fields or suburbs.

Myth: Tornadoes do not form in the winter, nor do they form in colder latitudes or on different continents than North America.

Tornadoes that form in winter are rare, but have been documented when warm air meets a strong storm front. For instance, a tornado struck Kenosha, Wisconsin on January 7, 2008.

Additionally, there have been many Canadian storms far north of the United States' Tornado Alley:

• The Edmonton Tornado of 1987, a powerful F4, struck the Metropolitan Edmonton, Alberta area, which is located 53.57 degrees north.

• A funnel cloud was sighted on Upper Garry Lake, Northwest Territories (now Nunavut), the most northerly funnel cloud on record in Canada. August 10, 1973.

• Yellowknife Tornado of 1978. A tornado touches down near Yellowknife, Northwest Territories toppling and destroying a transmission tower at Rae-Edzo. It was the third tornado in 16 years in the area.

• November 1989 Tornado Outbreak. A late-season tornado touched down on November 16, in Mont-Saint-Hilaire. It was rated F2.

• Sudbury, Ontario Tornado (August 20, 1970). A strong F3 tornado struck the Northern Ontario mining city of Sudbury, Ontario and its suburbs, with Lively, Ontario being the hardest hit in the early morning hours. This is the first recorded major tornado in Northern Ontario. The terrain is not too hilly (actually fairly flat for Northern Ontario standards), but its strength is unusual for its location.

• Elie, Manitoba Tornado. A violent F5 struck the town, lifting well-built houses from their foundation. After being originally classified as a strong F4, further damage surveys later confirmed the twister's F5 status.

Additionally, tornadoes can occur in Mexico, Australia, England, Russia, Brazil, Bangladesh, and many other areas apart from the United States and Canada. Note also that tornadoes can form at any time in any area under the effect of a hurricane or typhoon.

See also

• List of tornadoes and tornado outbreaks
• List of Canadian tornadoes
• Tornado records
• List of tornadoes striking downtown areas
• Tornadoes of 2007
• List of F5 and EF5 tornadoes

External links

• NWS Presentation on Deaths Due to Use of Underpasses as Shelters
• Snopes hurricane beliefs
• Snopes Twister beliefs
• National Hurricane Center
• Tornado Project "myth" page
• Tornado Alley, USA
• Tornado Myths (Tornado Pictures Website)
• Tornado Myths and Tornado Reality