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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 thunderstorm, also known as an electrical storm or a lightning storm, is a storm characterized by the presence of lightning and its acoustic effect on the Earth's atmosphere, known as thunder. Relatively weak thunderstorms are sometimes called thundershowers. Thunderstorms occur in a type of cloud known as a cumulonimbus. They are usually accompanied by strong winds and often produce heavy rain and sometimes snow, sleet, or hail, but some thunderstorms produce little precipitation or no precipitation at all. Thunderstorms may line up in a series or become a rainband, known as a squall line. Strong or severe thunderstorms include some of the most dangerous weather phenomena, including large hail, strong winds, and tornadoes. Some of the most persistent severe thunderstorms, known as supercells, rotate as do cyclones. While most thunderstorms move with the mean wind flow through the layer of the troposphere that they occupy, vertical wind shear sometimes causes a deviation in their course at a right angle to the wind shear direction.
A supercell is a thunderstorm characterized by the presence of a mesocyclone: a deep, persistently rotating updraft. Due to this, these storms are sometimes referred to as rotating thunderstorms. Of the four classifications of thunderstorms, supercells are the overall least common and have the potential to be the most severe. Supercells are often isolated from other thunderstorms, and can dominate the local weather up to 32 kilometres (20 mi) away. They tend to last 2–4 hours.
A tornado warning is a public warning that is issued to an area in the direct path of a tornado or a thunderstorm capable of producing a tornado. They are issued by weather forecasting agencies in some countries when an actual tornado or signs of a developing tornado, such as a funnel cloud or wall cloud, are reported by weather spotters, the public, or detected by weather radar.
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.
A severe thunderstorm warning is a type of public warning for severe weather that is issued by weather forecasting agencies worldwide when one or more severe thunderstorms have been detected by Doppler weather radar, observed by weather spotters, or reported by an emergency management agency, law enforcement, or the general public. Unlike a watch, a warning is issued to areas in the direct path of active severe thunderstorms, that are expecting a direct impact typically within an hour. Severe thunderstorms can cause property damage and injury due to large hail, high winds, and flooding due to torrential rainfall. The exact criteria to issue a warning varies from country to country.
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 and Ontario and Kansas.
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.
The Daulatpur–Saturia tornado occurred in Manikganj District, Bangladesh on April 26, 1989. There is great uncertainty about the death toll, but estimates indicate that it was devastating and that it killed approximately 1,300 people, which would make it the deadliest tornado in history. 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.
On March 28, 1920, a large outbreak of at least 37 tornadoes, 31 of which were significant, took place across the Midwestern and Southern United States. The tornadoes left at least 153 dead and at least 1,215 injured. Many communities and farmers alike were caught off-guard as the storms moved to the northeast at speeds that reached over 60 mph (97 km/h). Most of the fatalities occurred in Georgia (37), Ohio (28), and Indiana (21), while the other states had lesser totals. Little is known about many of the specific tornadoes that occurred, and the list below is only partial.
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 March 2009 tornado outbreak sequence was a series of tornado outbreaks which affected large portions of the Central, Southern, and Eastern United States from March 23 to March 29. A total of 56 tornadoes touched down during the event, two of which were rated as EF3.
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 tornado outbreak of August 8–9, 1993 was a small tornado outbreak that occurred over the Upper Midwest of the United States for a period of two days. An F0 tornado near Littlefork, Minnesota lifted and moved a mobile home, killing its two occupants. It is Minnesota's most recent single tornado to cause multiple deaths. Other minor tornadoes occurred in Minnesota, Iowa and Wisconsin, causing limited damage.
This page documents the tornadoes and tornado outbreaks of 1998, primarily in the United States. Most tornadoes form in the U.S., although some events may take place internationally. Tornado statistics for older years like this often appear significantly lower than modern years due to fewer reports or confirmed tornadoes, however by the 1990s tornado statistics were coming closer to the numbers we see today.
From April 13 to 16, 2012, a major tornado outbreak occurred across a large portion of the Great Plains. The storms resulted in six tornado-related fatalities, all of which occurred as a result of a nighttime EF3 tornado that caused major damage in and around Woodward, Oklahoma. Numerous other tornadoes occurred, including a violent EF4 tornado that passed near Marquette, Kansas, and an EF3 that caused major damage in Wichita.
The following is a glossary of tornado terms. It includes scientific as well as selected informal terminology.
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.
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.