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A tornado is a violently 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. It is often referred to as a twister, whirlwind or cyclone, although the word cyclone is used in meteorology to name a weather system with a low-pressure area in the center around which, from an observer looking down toward the surface of the Earth, winds blow counterclockwise in the Northern Hemisphere and clockwise in the Southern. Tornadoes come in many shapes and sizes, and they are often visible in the form of a condensation funnel originating from the base of a cumulonimbus cloud, with a cloud of rotating debris and dust beneath it. Most tornadoes have wind speeds less than 180 kilometers per hour, are about 80 meters across, and travel several kilometers before dissipating. The most extreme tornadoes can attain wind speeds of more than 480 kilometers per hour (300 mph), are more than 3 kilometers (2 mi) in diameter, and stay on the ground for more than 100 km (62 mi).
A tornado warning is a public warning that is issued by weather forecasting agencies to an area in the direct path of a tornado, or a thunderstorm capable of producing one, and advises individuals in that area to take cover. Modern weather surveillance technology such as Doppler weather radar can detect rotation in a thunderstorm, allowing for early warning before a tornado develops. They are also commonly issued based on reported visual sighting of a tornado, funnel cloud, or wall cloud, typically from weather spotters or the public, but also law enforcement or local emergency management. When radar is unavailable or insufficient, such ground truth is crucial. In particular, a tornado can develop in a gap of radar coverage, of which there are several known in the United States.
A tornado watch is a severe weather watch product of the National Weather Service that is issued by national weather forecasting agencies when meteorological conditions are favorable for the development of severe thunderstorms capable of producing tornadoes. In addition to the potential for tornado development, thunderstorms that develop within the watch area may contain large hail, straight-line winds, intense rainfall and/or flooding that pose a similar damage risk as the attendant tornado threat. A tornado watch does not mean a tornado is active or will appear, just that favorable conditions increases the likelihood of such happening. A watch must not be confused with a tornado warning.
The 1999 Oklahoma tornado outbreak was a significant tornado outbreak that affected much of the Central and parts of the Eastern United States, with the highest record-breaking wind speeds of 301 ± 20 mph (484 ± 32 km/h). During this week-long event, 154 tornadoes touched down. More than half of them were on May 3 and 4 when activity reached its peak over Oklahoma, Kansas, Nebraska, Texas, and Arkansas.
The 1990 Plainfield tornado was a devastating tornado that occurred on the afternoon of Tuesday, August 28, 1990. The violent tornado killed 29 people and injured 353. It is the only F5/EF5 rated tornado ever recorded in August in the United States, and the only F5 tornado to strike the Chicago area. There are no known videos or photographs of the tornado itself; however, in 2011, a video surfaced online showing the supercell that spawned the tornado. The Plainfield tornado was part of a small outbreak that produced several tornadoes in the Northern United States, specifically Kansas, and the Canadian province of Ontario.
A deadly tornado outbreak occurred in Central Texas during the afternoon and evening of May 27, 1997, in conjunction with a southwestward-moving cluster of supercell thunderstorms. These storms produced 20 tornadoes, mainly along the Interstate 35 corridor from northeast of Waco to north of San Antonio. The strongest tornado was an F5 tornado that leveled parts of Jarrell, killing 27 people and injuring 12 others. Overall, 30 people were killed and 33 others were hospitalized by the severe weather.
A deadly series of at least 33 tornadoes hit at least 10 different U.S. states on May 9–11, 1953. Tornadoes appeared daily from Minnesota in the north to Texas in the south. The strongest and deadliest tornado was a powerful F5 tornado that struck Waco, Texas on May 11, causing 114 of the 144 deaths in the outbreak. Alongside the 1902 Goliad tornado, it was the deadliest tornado in Texas history and is the 11th deadliest tornado in U.S. history. The tornado's winds demolished more than 600 houses, 1,000 other structures, and over 2,000 vehicles. 597 injuries occurred, and many survivors had to wait more than 14 hours for rescue. The destruction dispelled a myth that the geography of the region spared Waco from tornadoes, and along with other deadly tornadoes in 1953, the Waco disaster was a catalyst for advances in understanding the link between tornadoes and radar-detected hook echoes. It also generated support for improved civil defense systems, the formation of weather radar networks, and improved communications between stakeholders such as meteorologists, local officials, and the public.
The Windsor Locks, Connecticut tornado struck the towns of Windsor, Windsor Locks, and Suffield, Connecticut, and Feeding Hills, Massachusetts, on Wednesday, October 3, 1979. The short-lived but intense tornado struck without warning and caused three deaths and 500 injuries along its 11.3-mile (18.2 km) track. It received a rating of F4 on the Fujita scale, one of only three F4 tornadoes in Connecticut's history.
An anticyclonic tornado is a tornado which rotates in a clockwise direction in the Northern Hemisphere and a counterclockwise direction in the Southern Hemisphere. The term is a naming convention denoting the anomaly from normal rotation which is cyclonic in upwards of 98 percent of tornadoes. Many anticyclonic tornadoes are smaller and weaker than cyclonic tornadoes, forming from a different process, as either companion/satellite tornadoes or nonmesocyclonic tornadoes.
The Edmonton tornado of 1987, an event also known as Black Friday to Edmontonians, was a powerful and devastating tornado that ripped through the eastern parts of Edmonton, Alberta, Canada and parts of neighbouring Strathcona County on the afternoon of Friday, July 31, 1987. It was one of seven other tornadoes in central Alberta the same day.
The Daulatpur–Saturia tornado occurred in Manikganj District, Bangladesh on 26 April 1989. There is great uncertainty about the death toll, but official estimates from the World Meteorological Organization indicate that it was devastating and that it killed approximately 1,300 people, which would make it the deadliest tornado in history. In 2022, this tornado's status as the deadliest tornado in history was challenged, claiming it did not kill more than 922 people. The tornado affected the cities of Daulatpur and Saturia the most, moving east through Daulatpur and eventually northeast into Saturia. Previously, the area that the tornado hit had been in a state of drought for six months.
A series of destructive severe thunderstorms struck southeastern Queensland, Australia, on 29 November 1992. The storms produced strong winds, flash flooding and large hailstones in the region, including the capital city of Brisbane. The storms also spawned two of the most powerful tornadoes recorded in Australia, including the only Australian tornado to be given an official 'F4' classification on the Fujita scale and the last violent tornado in Australia until 21 March 2013.
The Tornado outbreak of June 7–8, 1984 was a significant severe weather and tornado event that took place across the central United States from North Dakota to Kansas on June 7–8, 1984. The tornado outbreak produced several significant tornadoes including an F5 tornado which traveled through Barneveld, Wisconsin, in the early hours of June 8, 1984. The entire outbreak killed at least 13 people across three states including 9 in Barneveld alone.
The Upper Great Lakes severe weather outbreak of August 23, 1998 was a severe weather outbreak that affected parts of Wisconsin, and the Upper Peninsula of Michigan. The outbreak occurred on August 23, 1998, and caused millions of dollars in damage to the region. One fatality is attributed to this severe weather event, when a severe thunderstorm knocked a tree onto a camper killing its sole occupant. A supercell spawned a F3 tornado that ripped across Door County causing $6.5 million in damages. It was the 8th most costly tornado in Wisconsin history injuring two people, destroying multiple structures and disrupting the regional economy and tourism. Two storms moved through the Fox Valley producing a minimal F0 tornado, but devastating amounts of hail. Damages from the hail were estimated to be around $5 million and damaged many structures and vehicles. Wisconsin Governor Tommy Thompson requested a Presidential Disaster Declaration from President Bill Clinton for the disaster, but was denied.
On June 18, 2001, a small, but fatal tornado outbreak occurred across the Upper Midwest as well as Florida. The outbreak spawned a long-tracked F3 tornado that killed three people, and caused approximately US$10 million in damage. The tornado struck Siren, Wisconsin, a small village whose only siren was malfunctioning when the tornado moved through. Other less damaging tornadoes were confirmed in Florida, Iowa, Minnesota and Nebraska. Following the outbreak, areas affected by the Wisconsin tornado received financial assistance from local and federal authorities.
The following is a glossary of tornado terms. It includes scientific as well as selected informal terminology.
A localized but devastating series of severe thunderstorms affected the Great Lakes region during May 20-21, 1953. The strongest of these storms produced three intense, long-tacked tornadoes in Iowa, Michigan, and Ontario. The worst tornado event was a violent F4 tornado that tore through the cities of Port Huron, Michigan, and Sarnia, Ontario, on May 21, damaging or destroying hundreds of structures and causing dozens of casualties. Overall, the tornadoes killed eight people, injured 123 others, and caused at least $17.6 million (1953 USD) in damage. Thunderstorm winds also caused an additional fatality when a tree fell on a house in Waterloo, Iowa.
A destructive and deadly outbreak of 17 tornadoes occurred on February 9–10, 1959, mostly during the overnight hours, causing widespread destruction in the Midwest and Southeast regions of the United States. The strongest of the outbreak was a violent F4 tornado which tore through Northwestern Downtown St. Louis. An F3 tornado also caused heavy damage to numerous structures in Southern Highland County, Ohio, including a school that was in session at the time the tornado hit. Overall, the outbreak caused 21 fatalities, 358 injuries, and $53.713 million in damage. Non-tornadic impacts also caused two more fatalities, and at least 70 more injuries.
An outbreak of seven tornadoes struck the Central Plains and Mississippi in Late-April 1950. Five of the seven tornadoes were significant (F2+), including two violent F4 tornadoes in Texas and Oklahoma, both of which killed five. Overall, the outbreak killed 11, injured 38, and caused $1.575 million in damage. A lightning strike at Lake Texoma in Oklahoma caused an additional fatality and injury as well.
A destructive outbreak sequence triggered 13 tornadoes from Nebraska to Virginia. The most and strongest tornadic activity, as well as most of the casualties, including all the deaths, came on June 27, when a catastrophic early-morning F4 tornado killed five and injured 100 in Kansas while two F3 tornadoes caused a combined 50 injuries and one fatality in Illinois later that afternoon. Overall, the outbreak sequence killed six, injured 161, and caused $10.283 million in damage.
References
- 1 2 Wakimoto, Roger M. (1983). "The West Bend, Wisconsin Storm of 4 April 1981:A Problem in Operational Meteorology". Journal of Climate and Applied Meteorology. 22 (1): 181. Bibcode:1983JApMe..22..181W. doi: 10.1175/1520-0450(1983)022<0181:TWBWSO>2.0.CO;2 . ISSN 1520-0450.
- ↑ Hayes, Paul (April 5, 1981). "Sudden shift in weather set the stage". The Milwaukee Journal. Retrieved 28 February 2010.
- 1 2 "Event Record Details". National Climatic Data Center (NCDC). Retrieved 28 February 2010.[ permanent dead link ]
- 1 2 Elving, Ron (April 5, 1981). "West Bend Surveys its damage". The Milwaukee Journal. Retrieved 28 February 2010.
- ↑ Duffy, Shatzi (April 9, 1981). "Tornado damage causes institute classes to scatter". The Milwaukee Journal. Retrieved 28 February 2010.
- ↑ Romell, Rick (April 8, 1981). "Broadcast was too 'vague' for tornado siren, police say". The Milwaukee Sentinel. Archived from the original on January 24, 2013. Retrieved 28 February 2010.