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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.
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.
The Storm Prediction Center (SPC) is a US government agency that is part of the National Centers for Environmental Prediction (NCEP), operating under the control of the National Weather Service (NWS), which in turn is part of the National Oceanic and Atmospheric Administration (NOAA) of the United States Department of Commerce (DoC).
The National Severe Storms Laboratory (NSSL) is a National Oceanic and Atmospheric Administration (NOAA) weather research laboratory under the Office of Oceanic and Atmospheric Research. It is one of seven NOAA Research Laboratories (RLs).
On February 21–23, 1998, a devastating tornado outbreak affected portions of the Southeastern United States, primarily the U.S. state of Florida. Sometimes known as the Night of the Tornadoes, it was the deadliest tornado event in Florida history. In all, 15 tornadoes touched down, one of which was long lived and tracked for nearly 40 miles (64 km). Affecting mainly the Interstate 4 (I-4) corridor of Central Florida, including the Greater Orlando area, the tornadoes—among the strongest ever recorded in Florida—produced near-violent damage, killed 42 people, and caused 259 injuries.
An extremely rare wintertime tornado outbreak affected the Midwestern United States on January 24, 1967. Of the 30 confirmed tornadoes, 13 occurred in Iowa, nine in Missouri, seven in Illinois, and one in Wisconsin. The outbreak produced, at the time, the northernmost tornado to hit the United States in winter, in Wisconsin, until January 7, 2008. The tornadoes formed ahead of a deep storm system in which several temperature records were broken. The deadliest and most damaging tornado of the outbreak struck Greater St. Louis at F4 intensity, killing three people and injuring 216.
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.
On Monday, April 8, 1957, a widespread tornado outbreak struck the Southeastern United States, particularly the Carolinas, and was responsible for seven deaths and 203 injuries across the region. Most of the activity occurred on either side of the Piedmont, including portions of the Cumberland Plateau. At least 18 tornadoes occurred, including several long-tracked tornado families, one of which included a violent tornado that was retrospectively rated F4 on the Fujita scale. Besides tornadoes, the outbreak also generated other severe weather phenomena such as large hail.
Severe weather is any dangerous meteorological phenomenon with the potential to cause damage, serious social disruption, or loss of human life. Types of severe weather phenomena vary, depending on the latitude, altitude, topography, and atmospheric conditions. High winds, hail, excessive precipitation, and wildfires are forms and effects of severe weather, as are thunderstorms, downbursts, tornadoes, waterspouts, tropical cyclones, and extratropical cyclones. Regional and seasonal severe weather phenomena include blizzards (snowstorms), ice storms, and duststorms. Extreme weather phenomena which cause extreme heat, cold, wetness or drought often will bring severe weather events. One of the principal effects of anthropogenic climate change is changes in severe and extreme weather patterns.
On March 21–22, 1952, a severe tornado outbreak generated eleven violent tornadoes across the Southern United States, which is the fourth-largest number of F4–F5 events produced by a single outbreak. Only the 1965 Palm Sunday tornado outbreak, the 1974 Super Outbreak, and the 2011 Super Outbreak surpassed this number. The outbreak caused 209 fatalities–50 of which occurred in a single tornado in Arkansas. The severe weather event also resulted in the fourth-largest number of tornado fatalities within a 24-hour period since 1950.
On March 16–17, 1942, a deadly late-winter tornado outbreak struck a large area of the Central and Southern United States. The tornado outbreak killed 149 people and injured at least 1,312. At least five states reported violent tornadoes, from Illinois and Indiana south to Mississippi, beginning with an F4 tornado in the morning in Illinois. Intense activity spread south to the Gulf Coast and north to the Michigan–Indiana border as the day went on. Seven violent tornadoes were reported, one of which was a powerful F5 in Illinois. The outbreak also produced eighteen tornadoes that caused at least one death, one of the highest such totals for a single outbreak.
On March 17, 1983, a significant severe weather event affected the southern Florida peninsula, including the Miami metropolitan area. A total of at least five tornadoes affected the region; while as many as 17 were reported, only two were confirmed in the official National Weather Service records. The strongest tornado produced F2 damage on the Fujita scale and skipped across the Everglades region from the eastern Big Cypress National Preserve through the Everglades and Francis S. Taylor Wildlife Management Area to Lighthouse Point—a path length of nearly 53 mi (85 km). An F1 tornado also affected Naples and Golden Gate. Additionally, unconfirmed tornadoes affected an RV park southeast of East Naples, as well as the Stuart and Jupiter areas, respectively. In addition to tornadoes, severe thunderstorms produced hail to 1 in (2.5 cm) in diameter, as well as rainfall totals of 1 to 2 in in some areas.
From May 3 to May 11, 2003, a prolonged and destructive series of tornado outbreaks affected much of the Great Plains and Eastern United States. Most of the severe activity was concentrated between May 4 and May 10, which saw more tornadoes than any other week-long span in recorded history; 335 tornadoes occurred during this period, concentrated in the Ozarks and central Mississippi River Valley. Additional tornadoes were produced by the same storm systems from May 3 to May 11, producing 363 tornadoes overall, of which 62 were significant. Six of the tornadoes were rated F4, and of these four occurred on May 4, the most prolific day of the tornado outbreak sequence; these were the outbreak's strongest tornadoes. Damage caused by the severe weather and associated flooding amounted to US$4.1 billion, making it the costliest U.S. tornado outbreak of the 2000s. A total of 50 deaths and 713 injuries were caused by the severe weather, with a majority caused by tornadoes; the deadliest tornado was an F4 that struck Madison and Henderson counties in Tennessee, killing 11.
On December 18–20, 1957, a significant tornado outbreak sequence affected the southern Midwest and the South of the contiguous United States. The outbreak sequence began on the afternoon of December 18, when a low-pressure area approached the southern portions of Missouri and Illinois. Supercells developed and proceeded eastward at horizontal speeds of 40 to 45 miles per hour, yielding what was considered the most severe tornado outbreak in Illinois on record so late in the calendar year. Total losses in the state were estimated to fall within the range of $8–$10 million.
From April 27–29, 1912, a major tornado outbreak generated at least six violent tornadoes in Oklahoma, with near-constant activity until early the next day. At least 15 cities were affected, 40 people died, and 120 others were injured. Tornado researcher Thomas P. Grazulis considered this outbreak to be among the worst on record in the state of Oklahoma, as measured by fatalities and violent tornadoes. At least five strong tornadoes affected Washita County, Oklahoma, during this outbreak.
On Friday, May 5, 1961, a strong tornado impacted the city of St. Petersburg, Florida. The tornado, which only touched down briefly, was estimated to have produced F2 damage on the Fujita scale. It struck the Northeast High School and the nearby Meadowlawn neighborhood in the extreme northern part of St. Petersburg, traveling 1⁄2 mi (0.80 km) and producing a 50-yard-wide (46 m) path. The tornado was part of a much larger outbreak sequence that produced 73 tornadoes. The parent thunderstorm that spawned the tornado was also attended by 3⁄4-inch-diameter (1.9 cm) hail.
The following is a glossary of tornado terms. It includes scientific as well as selected informal terminology.
On April 18–20, 1880, a tornado outbreak impacted the Midwestern United States, producing numerous strong tornadoes, killing at least 166 people, and injuring more than 516 others. The outbreak generated five violent tornadoes, including three long-tracked F4s in Missouri that killed at least 144 people. Two of the tornadoes followed parallel paths and occurred simultaneously near Springfield, one of which devastated the town of Marshfield, causing 92 fatalities there. Other deadly, intense tornadoes occurred in the Great Lakes region and in Arkansas, including an F4 that destroyed a third of El Paso, Arkansas, killing four or more people.
Five scattered tornadoes touched down across the Great Plains and Midwestern United States on June 19, 1951. The event was highlighted by a large, violent F4 tornado family that moved through the western and northern suburbs of Minneapolis, causing all the tornadic casualties from the outbreak. In all, one person was killed, 20 others were injured, and damage was estimated at $52.5 million. There was one additional death and six injuries from non-tornadic events as well.
On Saturday, November 11, 1911, a regionally and seasonally significant tornado outbreak affected the Great Lakes region of the United States. The outbreak generated at least 13 tornadoes, including a violent, long-tracked F4 that impacted Wisconsin, killing at least nine people and injuring 50 more. Other intense tornadoes occurred in Illinois and Indiana, resulting in four additional fatalities. Several other tornadoes were reported from multiple states. In all, the outbreak killed 16 people and injured at least 101. Total losses exceeded $1.755 million. Tornado researcher Thomas P. Grazulis considered the outbreak to be the worst in the month of November on record at the time in the Great Lakes region.
References
- ↑ Scott, Michon (5 June 2015). "El Niño and La Niña affect spring tornadoes and hailstorms". NOAA Climate.gov. Retrieved 17 November 2018.
- ↑ Fritz, Angela (24 March 2015). "Is El Nino behind our record-slow start to tornado season? - Capital Weather Gang". Washington Post .
- ↑ John Allen, Central Michigan University College of Science and Engineering.
- ↑ "John Allen". Staff Directory. International Research Institute for Climate and Society. Archived from the original on 8 May 2014. Retrieved 17 May 2014.
- ↑ Revkin, Andrew C. (9 December 2013). "A Closer Look at Tornadoes in a Human-Heated Climate". The New York Times . Retrieved 17 May 2014.
- ↑ Baggaley, Kate (7 May 2014). "John Allen: Scientist with an Eye on the Storm". Climate Central . Retrieved 17 May 2014.