Tornado myths


Tornado myths

Tornado myths are common misconceptions and urban legends related to tornadoes. They often deal with tornado safety, the minimization of tornado damage, and false assumptions about the size, shape, power, and path of the tornado itself.

afety Myths

Using highway overpasses as shelter

The first notable instance of a person using a highway overpass for shelter from a tornado occurred on April 101979. A man stuck in a traffic jam as the tornado approached left his vehicle and lay flat on an embankment beneath an overpass, surviving an F4 tornado with only minor injuries. In 1991, a highly publicized event occurred in which a television crew and several others survived the passage of a tornado near El Dorado, Kansas by huddling underneath an overpass, bracing themselves against steel girders. The sensational footage taken by the television crew was broadcast across the United States. This and other media coverage helped to fuel the myth that the underside of bridges or overpasses are good shelters when a tornado strikes.

However, in the El Dorado tornado, several unique factors came together to protect the film crew and others seeking shelter under the bridge. The tornado did not pass directly over the filmed bridge, but instead tracked slightly south of the area, exposing the people there to winds less damaging than those in the tornado core. The overpass had an unusual design which included a hollow crawlspace at the top of the embankment, which was large enough to allow people to crawl inside and hold the exposed girders against the wind. This design also allowed for added protection against high-speed debris.

Unfortunately, these cases led to a false belief among many that highway overpasses were good shelter from a tornado. The belief was so strong among some that, in at least one case during the 1999 Oklahoma tornado outbreak, an 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. During the outbreak, a violent tornado directly struck three highway overpasses, and at each one there was a fatality. All of the individuals received massive injuries from tornadic debris, and several were swept into the tornado itself.

From lessons harshly learned in the 1999 Oklahoma outbreak, and for many scientific reasons, meteorologists insist that overpasses are insufficient shelter from tornado winds and debris, and may possibly be "the worst place" to be during a violent tornado. The embankment under an overpass is higher than the surrounding terrain, and the wind speed increases with height. Additionally, the overpass design may create a "wind-tunnel" effect under the span, increasing the winds further. Many overpasses are completely exposed underneath and most lack hanging girders or a crawlspace-like area to provide sufficient protection from debris, which can travel at deadly speeds even in weak tornadoes. Even worse, people stopping underneath overpasses blocks the flow of traffic, putting others in danger unnecessarily. [ [http://www.crh.noaa.gov/images/pah/pdf/tornadosafety.pdf Severe Weather Safety Guide] National Weather Service Paducah, Kentucky. Accessed 2008-06-22.]

afest location in a building

, with only a few interior walls still standing. [cite web|url= http://www.srh.noaa.gov/lch/events/111703.php|title= TORNADOES & SEVERE WEATHERNOVEMBER 17th & 18th, 2003|accessdate=2008-06-24|date=2008-03-06|publisher= National Weather Service, Lake Charles, Louisiana] ] In 1887, the first book on tornadoes was written by John Park Finley, a pioneer in the field of tornado research. While it was a revolutionary book containing many breakthrough ideas, it contained a few ideas which have since been proven false. One of these was the idea that the northeast or east part of a structure was the least safe, and should be avoided when seeking shelter from a tornado. This advice was unrefuted and heeded by many until the 1960s.cite web|url= http://www.tornadoproject.com/myths/myths.htm|title= Myths and Misconceptions about Tornadoes|accessdate=2008-06-24|year= 1999|publisher= Tornado Project]

This myth derived from two misconceptions: First, that tornadoes always travel in a northeasterly direction, and second, that debris from a structure will be carried away in the direction of the tornado's propagation, leaving unharmed anyone taking shelter on the side of the structure facing the tornado's approach. [http://www.crh.noaa.gov/mkx/?n=taw-part2-tornado_myths Severe Weather Awareness - Common Tornado Myths] National Weather Service Milwaukee/Sullivan, Wisconsin. Accessed 2008-06-22.] The seriousness of these misconceptions began to be revealed in the 1960s and 1970s, when surveys of major tornado damage in residential areas showed that the section of a house in the direction of the tornado's approach is actually the "least" safe. Additionally, many tornadoes have travelled in directions far from northeasterly, including the F5 Jarrell Tornado, which moved south-southwesterly. Because determining a tornado's direction of approach can waste precious time when seeking shelter, official advice is to seek shelter in an interior room on the lowest floor of a building, under a staircase, I-beam, or sturdy piece of furniture if possible.


=Opening windows to reduce tornado da

One of the oldest pieces of tornado folklore is the idea that tornadoes do most of their damage due to the lower atmospheric pressure at the center of a tornado, which causes the house to explode outward. As the theory goes, opening windows helps to equalize the pressure. [http://www.butlercountyohio.org/ema/pdf/tornado%20info%20for%20schools.pdf Tornado Information for Schools (PDF)] Butler County, Ohio Emergency Management Agency. Accessed 2008-06-25.]

The source of this myth is from the appearance of some destroyed structures after violent tornadoes. When one wall receives the extreme pressure of tornado winds, it will likely collapse "inward". This then leads to a considerable "outward" pressure on the three remaining walls, which fall outwards as the roof falls down, creating the impression of a house which has exploded. Indeed, damage surveys of "exploded" houses usually show at least one wall which has blown inward. Additionally, if the roof is lifted before any walls fail, the walls can fall in any direction. If they fall outward, this structure can also appear to have exploded. [Williams, Jack. (2004-08-20) [http://www.usatoday.com/weather/resources/askjack/watorsaf.htm Answers archive: Tornado safety] "The Weather Channel". Accessed 2008-06-25.]

In even the most violent tornadoes, there is only a pressure drop of about 10%, which is about convert|1.4|psi|kPa. Not only can this difference be equalized in most structures in approximately three seconds, but is a pressure insufficient to cause any sort of damage. Additionally, windows are the most fragile parts of a house, and in a significant tornado flying debris will likely break enough windows to equalize any pressure difference fairly quickly. Regardless of any pressure drop, the direct effects of tornado winds is enough to cause damage to a house in all but the weakest tornadoes.

Current advice is that opening windows in advance of a tornado wastes time that could be spent seeking shelter. Also, being near windows is a very dangerous place to be during a severe weather event, possibly exposing people to flying glass.

Escaping a tornado in a vehicle

Often people try to avoid or outrun a tornado in a vehicle. In theory, cars can travel faster than the average tornado, and so it is better to avoid the tornado altogether than take shelter in its path. [ [http://www.mb.ec.gc.ca/air/summersevere/ae00s26.en.html Tornado and Lightning Myths] "Environment Canada" Accessed 2008-06-25.]

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 all but the most violent tornadoes. Underground or above-ground tornado shelters, as well as extremely strong structures such as bank vaults, offer almost complete protection. Cars, on the other hand, can be heavily damaged by even weak tornadoes, and in violent tornadoes they can be thrown large distances, even into buildings. High-profile vehicles such as buses and tractor trailers are even more vulnerable to high winds. [http://www.tornadoproject.com/safety/cars.htm Tornado Safety in Cars] . Accessed 2008-07-07.]

There are many reasons to avoid cars when a tornado is imminent. Severe thunderstorms which produce tornadoes can produce flooding rains, hail, and strong winds far from the tornado-producing area, all of which can make driving difficult or even impossible. Some tornadoes can even move faster than cars, even when the road is clear and flat. Any of these situations can leave drivers stranded in the path of the tornado far from substantial shelter. When coupled with driver panic, they may also 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. cite web|url= http://www.srh.noaa.gov/oun/wxevents/19790410/burgess.php|title= The April 10, 1979 Severe Weather Outbreak|accessdate= 2008-06-22|last= Burgess|first= Don |date= 2006-06-13|publisher= National Weather Service Norman, Oklahoma]

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, or substantial shelter if nearby. [http://www.crh.noaa.gov/lmk/spotter_reference/spotter_slideshow/slide71.php Tornado Safety in Your Vehicle] ] Far-away, highly-visible tornadoes, however, can be successfully fled from at right angles (90-degree) from its direction of apparent movement. [ [http://spc.noaa.gov/faq/tornado/index.html The Online Tornado FAQ (by Roger Edwards, SPC) (Bot generated title)] ] 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. [ [http://www.crh.noaa.gov/lmk/spotter_reference/spotter_slideshow/slide69.php Tornado Safety in Your Mobile Home (Bot generated title)] ]

Tornado behavior

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

Tornadoes "skipping" houses

Several different phenomena have lent credence to the idea that tornadoes "skip". Tornadoes vary in intensity along their path, sometimes wildly. If a tornado were causing damage, then weakened to the point where it could cause no damage, followed by a re-intensification, it would appear is if it "skipped" a section. Occasionally, especially with violent tornadoes, a small suction vortex will completely destroy a structure next to another building which appears almost unscathed, apparently "skipped". [http://www.srh.noaa.gov/oun/office/faq.php?c=Tornadoes&i=Myths What are some common tornado myths?] National Weather Service Norman, Oklahoma. Accessed 2008-06-24] [http://www.spc.noaa.gov/faq/tornado/ The Online Tornado FAQ] Accessed 2008-06-24.]

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". [ [http://www.spc.noaa.gov/publications/mccarthy/tor30yrs.pdf Tornado Trends over the Past 30 Years] ]

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, leading to the term skipping tornado. 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.

Correlation of a tornado's size to its intensity

Some people have been led to assume that small, skinny tornadoes are always weaker than large, wedge-shaped tornadoes (see Tornado#Shape and Tornado#Size).

There is, in fact, an observed trend of wider tornadoes causing more severe damage. It is unknown whether this is due to an actual tendency of tornado dynamics or an ability for the tornado to affect a larger area. However, this is not a reliable indicator of an individual tornado's intensity. Some small, rope-like tornadoes, traditionally thought of as weak, have been among the strongest in history. Since 1990, at least 18 tornadoes half a mile wide or more have been rated F1 (or EF1) or lower. Data from the Storm Prediction Center archives, which are accessible through [http://www.spc.noaa.gov/software/svrplot2/ SeverePlot] , free software created and maintained by John Hart, lead forecaster for the SPC.] Also, tornadoes typically change shape during the course of their lifespan, further complicating any attempt to classify how dangerous a tornado is as it is occurring. cite web| url = http://www.weather.gov/os/brochures/adv_spotters.pdf| title = Advanced Spotters' Field Guide| accessdate = 2006-09-20| author = Doswell, Moller, Anderson et al.| year = 2005| format = PDF| publisher = [http://www.commerce.gov/ US Department of Commerce] ]

Tornadoes not appearing to reach the ground

It is commonly and mistakenly thought that if the condensation funnel of a tornado does not reach the ground, then the tornado can not cause substantial damage. 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. [http://www.weather.gov/os/brochures/adv_spotters.pdf]

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

Direction of travel

It has been thought in the distant past that tornadoes moved almost exclusively in a northeasterly direction. 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. [ [http://www.spc.noaa.gov/faq/tornado/#Safety The Online Tornado FAQ (by Roger Edwards, SPC) ] ]

Geographical influences

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

Tornadoes being "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.

Citation Needed - Skip says otherwise.

Tornadoes near rivers, valleys, mountains or other terrain features

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.

Tornadoes in downtown areas

More than 100 tornadoes have struck downtown areas of large cities in recorded history. Many cities have been struck twice or more, and a few, including London, have been struck by violent tornadoes (F4 or stronger).

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 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.

Tornadoes in the winter or at high latitudes

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. [ [http://www.wisn.com/weather/14996323/detail.html January Tornadoes Touch Down In Kenosha County - Milwaukee Weather News Story - WISN Milwaukee ] ]

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.

Tornadoes outside of North America

Tornadoes can occur in Mexico, Australia, England, Russia, Brazil, Bangladesh, and many other areas apart from the United States and Canada. Tornadoes often occur in the outer rainbands of tropical cyclones, which affect every continent except Antarctica.

References

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

* [http://lwf.ncdc.noaa.gov/oa/climate/severeweather/tornadosafety.html#myths Tornado Myths and Facts] "National Climatic Data Center"
* [http://www.snopes.com/movies/films/twister.htm Snopes Twister beliefs]
* [http://tornadopictures.net/content/view/13/28/ Tornado Myths] (Tornado Pictures Website)
* [http://www.hprcc.unl.edu/nebraska/tornado-myths.html Tornado Myths and Tornado Reality]


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