Anticyclonic tornado
An anticyclonic tornado is a tornado which rotates in a clockwise direction in the Northern Hemisphere and a counterclockwise direction in the Southern Hemisphere.[1] The term is a naming convention denoting the anomaly from normal rotation which is cyclonic in upwards of 98 percent of tornadoes.[citation needed] Many anticyclonic tornadoes are smaller and weaker than cyclonic tornadoes, forming from a different process, as either companion/satellite tornadoes or nonmesocyclonic tornadoes.[2]
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Formation
Most strong tornadoes form in the inflow and updraft area bordering the updraft-downdraft interface (which is also near the mesoscale "triple point") zone of supercell thunderstorms. The thunderstorm itself is rotating, with a rotating updraft known as a mesocyclone, and then a smaller area of rotation at lower altitude the tornadocyclone (or low-level mesocyclone) which produces or enables the smaller rotation that is a tornado. All of these may be quasi-vertically aligned continuing from the ground to the mid-upper levels of the storm. All of these cyclones and scaling all the way up to large extratropical (low-pressure systems) and tropical cyclones rotate cyclonically. Rotation in these synoptic scale systems stems partly from the Coriolis effect, but thunderstorms and tornadoes are too small to be significantly affected. The common property here is an area of lower pressure, thus surrounding air flows into the area of less dense air forming cyclonic rotation. The rotation of the thunderstorm itself is induced mostly by vertical wind shear, specifically clockwise turning as altitude increases (called a veered vertical profile, although backed profiles can occur with anticyclonic supercells]].
Various processes can produce an anticyclonic tornado. Most often they are satellite tornadoes of larger tornadoes which are directly associated with the tornadocyclone and mesocyclone. Occasionally anticyclonic tornadoes occur as an anticyclonic companion (mesoanticyclone) to a mesocyclone within a single storm. Anticyclonic tornadoes can occur as the primary tornado with a mesocyclone and under a rotating wall cloud. Also, anticyclonic supercells (with mesoanticyclone), which usually are storms that split and move to the left of the parent storm motion, though very rarely spawning tornadoes, spawn anticyclonic tornadoes. There is an increased incidence of anticyclonic tornadoes associated with tropical cyclones, and mesovortices within bow echoes may spawn anticyclonic tornadoes.[3]
The first anticyclonic tornado associated with a mesoanticyclone was spotted on WSR-88D weather radar in Sunnyvale, California May 4, 1998. The tornado was an F-2 on the Fujita Scale.[4]
Known "anticyclonic tornado" events
| Date | Location | Notes and References |
|---|---|---|
| 8 June 1951 | Corn, Oklahoma | First known tornado filmed in the US, a companion or cyclic tornado to another significant tornado[5] |
| 6 June 1975 | Freedom, Oklahoma | [6][7] |
| 13 June 1976 | Central Iowa | [8] |
| 6 April 1980 | Grand Island, Nebraska | [9] |
| 4 April 1981 | West Bend, Wisconsin | 1981 West Bend F4 anticyclonic tornado |
| 4 May 1998 | San Francisco Bay Area, California | [4] |
| 13 June 1998 | Northern Oklahoma City, Oklahoma | Started as a waterspout on Lake Hefner and then hit land[10] |
| 19 April 2002 | Lubbock, Texas | |
| 6 September 2004 | Chek-Lap-Kok International Airport, Hong Kong, China | [11] |
| 24 April 2006 | El Reno, Oklahoma | [2] |
| 20 June 2006 | Rushville, Nebraska | |
| 10 May 2010 | South-central Oklahoma | Two tornadoes associated with anticyclonic supercell[12] |
| 31 May 2013 | El Reno, Oklahoma | EF2 southeast of the 2013 EF3 El Reno tornado[13] |
| 4 June 2015 | Elbert County, Colorado | [14] |
| 31 March 2016 | ||
| 5 April 2017 | Shelbyville, Tennessee | [16] |
| 5 January 2019 | Seymour, Texas | Two possible and confirmation coming[citation needed] |
| 15 June 2019 | Estelline, South Dakota | Lasted approximately 45 seconds and damaged about 7 trees[17][18][19] |
| 19 April 2020 | Elko, Georgia | [20] |
See also
References
- ^ Edwards, Roger. "The Online Tornado FAQ". NWS Storm Prediction Center. Retrieved 2019-05-02.
- ^ a b Samenow, Jason (5 June 2013). "The rare "anticyclonic" tornado in El Reno, Okla.; not its first encounter". The Washington Post. Retrieved 9 April 2019.
- ^ Stull, Roland B. (2000). Meteorology for Scientists and Engineers (2nd ed.). Thomson Learning. ISBN 9780534372149.
- ^ a b Monteverdi, John P.; Blier, Warren; Stumpf, Greg; Pi, Wilfred; Anderson, Karl (November 2001). "First WSR-88D Documentation of an Anticyclonic Supercell with Anticyclonic Tornadoes: The Sunnyvale–Los Altos, California, Tornadoes of 4 May 1998". Monthly Weather Review. 129 (11): 2805–2814. Bibcode:2001MWRv..129.2805M. doi:10.1175/1520-0493(2001)129<2805:FWDOAA>2.0.CO;2.
- ^ Grazulis, Thomas (2003). The Tornado Natures Ultimate Windstorm. Norman, OK: University of Oklahoma Press. p. 237. ISBN 9780806135380. Retrieved 2 June 2020.
- ^ "Freedom, Oklahoma Anticyclonic Tornado - June 6, 1975". Youtube. cyclonejimcom. Retrieved 9 April 2019.
- ^ Grazulis, Thomas P. "Twister: Fury on the Plains (1995)". imdb. Music Video Productions (co-production); The Tornado Project. Retrieved 9 April 2019.
- ^ Brown, John M.; Knupp, Kevin R. (October 1980). "The Iowa Cyclonic-Anticyclonic Tornado Pair and Its Parent Thunderstorm". Monthly Weather Review. 108 (10): 1626–1646. Bibcode:1980MWRv..108.1626B. doi:10.1175/1520-0493(1980)108<1626:TICATP>2.0.CO;2.
- ^ Bunkers, Matthew J.; Stoppkotte, John W. (31 January 2007). "Documentation of a Rare Tornadic Left-Moving Supercell". Electronic Journal of Severe Storms Meteorology. 2 (2): 1–22. Retrieved 9 April 2019.
- ^ Morgan, Mike. "June 13, 1998: Rare OKC twister defies nature, spins clockwise". Oklahomas News 4. KFOR. Retrieved 15 June 2020.
- ^ Kosiba, Karen A.; Robinson, Paul; Chan, P. W.; Wurman, Joshua (2014). "Wind Field of a Nonmesocyclone Anticyclonic Tornado Crossing the Hong Kong International Airport". Advances in Meteorology. 2014 (597378). Hindawi: 1–7. doi:10.1155/2014/597378.
- ^ "The May 10, 2010 Tornado Outbreak in Oklahoma". National Weather Service Forecast Office - Norman, Oklahoma. 2010. Retrieved 2019-05-02.
- ^ Norman, N. W. S. (2013-06-04). "The tornado count for May 31 will rise as analysis continues, including an anticyclonic EF2 tornado SE of the El Reno tornado. #okwx". @NWSNorman. Retrieved 2019-09-24.
- ^ "Storm Damage Surveys for June 4th Tornadoes". Denver/Boulder, CO Weather Forecast Office. Retrieved 10 April 2019.
- ^ "March 31, 2016 Tornadoes". National Weather Service.
- ^ Edwards, Christina. "A "very unique event": Rare anticyclonic tornado touched down in southeastern Tennessee Wednesday". WHNT News (Channel 9 FOX). Retrieved 10 April 2019.
- ^ Donegan, Brian. "A Rare Clockwise-Rotating Tornado Touched Down in South Dakota Last Weekend". Weather.com. Weather.com. Retrieved 19 June 2019.
- ^ Bates, Becky. "Rare clockwise-spinning tornado touches down in South Dakota". KTVQ. KTVQ. Retrieved 19 June 2019.
- ^ Smith, Grant. "Rare anticyclonic tornado spotted in Deuel County". KELO. KELO. Retrieved 19 June 2019.
- ^ NWS Damage Survey for April 19th Tornado in Houston County (Report). Iowa Environmental Mesonet. April 20, 2020. Retrieved April 28, 2020.
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