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. Many anticyclonic tornadoes are smaller and weaker than cyclonic tornadoes, forming from a different process, as either companion/satellite tornadoes or nonmesocyclonic tornadoes.[2]

An anticyclonic tornado near Big Spring, Texas on May 22, 2016 captured by storm chaser Aaron Jayjack.

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 on May 4, 1998. The tornado was an F2 on the Fujita Scale.[4]

Known "anticyclonic tornado" events

DateF#/EF# RatingLocationNotes and References
8 June 1951F3Corn, OklahomaFirst known tornado filmed in the US, a companion or cyclic tornado to another significant tornado. It is officially listed as one tornado event by the CDNS report and the NCDC.[5][6]
6 June 1975F1Freedom, OklahomaOne of three tornadoes to touch down in the area.[7][8][9]
13 June 1976F3Jordan, IowaTornadoes of 1976#June 13 – A satellite tornado to the F5 Jordan, Iowa tornado.[10][11]
3 June 1980F1Grand Island, Nebraska1980 Grand Island tornado outbreak – First of three anticyclonic tornadoes in the area that night.[12][13]
3 June 1980F3Grand Island, Nebraska1980 Grand Island tornado outbreak – Second of three anticyclonic tornadoes in the area that night.[12][14]
3 June 1980F1Grand Island, Nebraska1980 Grand Island tornado outbreak – Last of three anticyclonic tornadoes in the area that night.[12][15]
4 April 1981F4West Bend, Wisconsin1981 West Bend tornado – Strongest anticyclonic tornado ever recorded.[16]
13 June 1998F2North Oklahoma City, OklahomaTornado outbreak of June 13, 1998 – Sixth of seven tornadoes to touch down from the same supercell.[17][18]
19 April 2002F0Lubbock, Texas"The tornado was produced by an antimesocyclone, which was located on the north flank of a left-split storm."[19]
6 September 2004F?Chek-Lap-Kok International Airport, Hong KongDescribed as a marginal tornado.[20]
24 April 2006F1El Reno, OklahomaSecond of two F1 tornadoes in the area.[21][2]
20 June 2006F1Rushville, NebraskaA house, sheds, and outbuildings were destroyed on a farmstead.[22]
2 October 2007EF0Bussey, IowaTornadoes of 2007#October 2 – This brief anticyclonic touched down in an open field southeast of Bussey, doing no damage.[23]
10 May 2010EF0Nardin, OklahomaTornado outbreak of May 10–13, 2010 – First of five anticyclonic on this day.[24][25]
10 May 2010EF1Bray, OklahomaTornado outbreak of May 10–13, 2010 – Second of five anticyclonic tornadoes on this day; was very large at times.[24][26]
10 May 2010EF1Southern Norman, OklahomaTornado outbreak of May 10–13, 2010 – Third of five anticyclonic tornadoes on this day; it was likely a satellite tornado to the Norman–Little Axe, Oklahoma EF4 tornado.[24][27]
10 May 2010EF1Wayne, OklahomaTornado outbreak of May 10–13, 2010 – Fourth of five anticyclonic tornadoes on this day; was up to a 1⁄2 mi (0.80 km) wide and was briefly accompanied by a cyclonic EF0 satellite tornado.[24][28]
10 May 2010EF1Lake Eufaula, OklahomaTornado outbreak of May 10–13, 2010 – Last of five anticyclonic tornadoes on this day; was up to a 5⁄8 mi (1.0 km) wide.[24][29]
31 May 2013EF2Yukon, OklahomaTornado outbreak of May 26–31, 2013 – A long-lived strong satellite tornado that was southeast of the record-breaking EF3 El Reno tornado.[30][31]
4 June 2015EF0Simla, ColoradoTornadoes of 2015#June 4 – A brief anticyclonic tornado caused no damage.[32][33]
4 June 2015EF0Kutch, ColoradoTornadoes of 2015#June 4 – A brief anticyclonic tornado caused no damage.[32][34]
31 March 2016EF0Hohenwald, TennesseeTornadoes of 2016#March 30–April 1 – A brief anticyclonic tornado snapped and uprooted trees, downed several large tree branches and inflicted minor roof damage to a home and barn.[35][36]
5 April 2017EF1Shelbyville, TennesseeTornadoes of 2017#April 4–6 – A landspout anticyclonic tornado snapped damaged trees, cars, and structures.[37][38]
15 June 2019EF0Johnsonville, South DakotaTornadoes of 2019#June 15–16 – This tornado lasted approximately 45 seconds and damaged about seven trees.[39][40][41][42]
29 July 2021EF0Bustleton, Philadelphia, PennsylvaniaTornado outbreak of July 28–29, 2021 – A weak tornado damaged buildings and trees.[43]
27 August 2021EF0Dougherty, Iowa"This very brief track was found in Sentinel satellite imagery and stayed in fields for its existence. Based on the location in the supercell, inflow wind trajectories along the left side of the track, and striation patterns in the fields, there is a high likelihood that this was an anti-cyclonic tornado."[44]

See also

References

  1. ↑ Edwards, Roger. "The Online Tornado FAQ". NWS Storm Prediction Center. Retrieved 2019-05-02.
  2. 1 2 Samenow, Jason (5 June 2013). "The rare "anticyclonic" tornado in El Reno, Okla.; not its first encounter". The Washington Post. Retrieved 9 April 2019.
  3. ↑ Stull, Roland B. (2000). Meteorology for Scientists and Engineers (2nd ed.). Thomson Learning. ISBN 9780534372149.
  4. ↑ 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. S2CID 35163346.
  5. ↑ "Oklahoma Event Report: F3 Tornado". National Centers for Environmental Information. National Weather Service. Retrieved 25 May 2022.
  6. ↑ Grazulis, Thomas (2003). The Tornado Natures Ultimate Windstorm. Norman, OK: University of Oklahoma Press. p. 237. ISBN 9780806135380. Retrieved 2 June 2020.
  7. ↑ "Oklahoma Event Report: F1 Tornado". National Centers for Environmental Information. National Weather Service. Retrieved 25 May 2022."Oklahoma Event Report: F1 Tornado". National Centers for Environmental Information. National Weather Service. Retrieved 25 May 2022."Oklahoma Event Report: F1 Tornado". National Centers for Environmental Information. National Weather Service. Retrieved 25 May 2022.
  8. ↑ "Freedom, Oklahoma Anticyclonic Tornado - June 6, 1975". Youtube. cyclonejimcom. Archived from the original on 2021-12-21. Retrieved 9 April 2019.
  9. ↑ Grazulis, Thomas P. "Twister: Fury on the Plains (1995)". imdb. Music Video Productions (co-production); The Tornado Project. Retrieved 9 April 2019.
  10. ↑ "Iowa Event Report: F3 Tornado". National Centers for Environmental Information. National Weather Service. Retrieved 25 May 2022.
  11. ↑ 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.
  12. 1 2 3 "NWS Hastings: June 3, 1980 Grand Island Tornadoes". NWS. Retrieved April 18, 2019.
  13. ↑ "Nebraska Event Report: F1 Tornado". National Centers for Environmental Information. National Weather Service. Retrieved 25 May 2022.
  14. ↑ "Nebraska Event Report: F3 Tornado". National Centers for Environmental Information. National Weather Service. Retrieved 25 May 2022."Nebraska Event Report: F3 Tornado". National Centers for Environmental Information. National Weather Service. Retrieved 25 May 2022.
  15. ↑ "Nebraska Event Report: F1 Tornado". National Centers for Environmental Information. National Weather Service. Retrieved 25 May 2022."Nebraska Event Report: F1 Tornado". National Centers for Environmental Information. National Weather Service. Retrieved 25 May 2022.
  16. ↑ "Wisconsin Event Report: F4 Tornado". National Centers for Environmental Information. National Weather Service. Retrieved 25 May 2022.
  17. ↑ "Oklahoma Event Report: F2 Tornado". National Centers for Environmental Information. National Weather Service. Retrieved 25 May 2022.
  18. ↑ Morgan, Mike (13 June 2020). "June 13, 1998: Rare OKC twister defies nature, spins clockwise". Oklahomas News 4. KFOR. Retrieved 15 June 2020.
  19. ↑ "Texas Event Report: F0 Tornado". National Centers for Environmental Information. National Weather Service. Retrieved 25 May 2022.
  20. ↑ 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. Hindawi. 2014 (597378): 1–7. doi:10.1155/2014/597378.
  21. ↑ "Oklahoma Event Report: F1 Tornado". National Centers for Environmental Information. National Weather Service. Retrieved 25 May 2022.
  22. ↑ "Nebraska Event Report: F1 Tornado". National Centers for Environmental Information. National Weather Service. Retrieved 25 May 2022.
  23. ↑ "Iowa Event Report: EF0 Tornado". National Centers for Environmental Information. National Weather Service. Retrieved 10 June 2022.
  24. 1 2 3 4 5 "The May 10, 2010 Tornado Outbreak in Oklahoma". National Weather Service Forecast Office - Norman, Oklahoma. 2010. Retrieved 2019-05-02.
  25. ↑ "Oklahoma Event Report: EF0 Tornado". National Centers for Environmental Information. National Weather Service. Retrieved 25 May 2022.
  26. ↑ "Oklahoma Event Report: EF1 Tornado". National Centers for Environmental Information. National Weather Service. Retrieved 25 May 2022."Oklahoma Event Report: EF1 Tornado". National Centers for Environmental Information. National Weather Service. Retrieved 25 May 2022.
  27. ↑ "Oklahoma Event Report: EF1 Tornado". National Centers for Environmental Information. National Weather Service. Retrieved 25 May 2022.
  28. ↑ "Oklahoma Event Report: EF1 Tornado". National Centers for Environmental Information. National Weather Service. Retrieved 25 May 2022.
  29. ↑ "Oklahoma Event Report: EF1 Tornado". National Centers for Environmental Information. National Weather Service. Retrieved 25 May 2022.
  30. ↑ "Oklahoma Event Report: EF2 Tornado". National Centers for Environmental Information. National Weather Service. Retrieved 25 May 2022.
  31. ↑ 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.
  32. 1 2 "Storm Damage Surveys for June 4th Tornadoes". Denver/Boulder, CO Weather Forecast Office. Retrieved 10 April 2019.
  33. ↑ Colorado Event Report: EF0 Tornado (Report). National Climatic Data Center. National Weather Service Weather Forecast Office in Boulder, Colorado. 2015. Retrieved November 3, 2015.
  34. ↑ Colorado Event Report: EF0 Tornado (Report). National Climatic Data Center. National Weather Service Weather Forecast Office in Boulder, Colorado. 2015. Retrieved November 3, 2015.
  35. ↑ Tennessee Event Report: EF0 Tornado (Report). National Centers for Environmental Information. National Weather Service Weather Forecast Office in Nashville, Tennessee. 2016. Retrieved November 30, 2016.
  36. ↑ "March 31, 2016 Tornadoes". National Weather Service.
  37. ↑ Edwards, Christina (7 April 2017). "A "very unique event": Rare anticyclonic tornado touched down in southeastern Tennessee Wednesday". WHNT News (Channel 9 FOX). Retrieved 10 April 2019.
  38. ↑ Tennessee Event Report: EF0 Tornado (Report). National Centers for Environmental Information. National Weather Service Weather Forecast Office in Nashville, Tennessee. 2017. Retrieved November 2, 2017.
  39. ↑ South Dakota Event Report: EF0 Tornado (Report). National Centers for Environmental Information. National Weather Service Weather Forecast Office in Aberdeen, South Dakota. 2019. Retrieved January 12, 2020.
  40. ↑ Donegan, Brian. "A Rare Clockwise-Rotating Tornado Touched Down in South Dakota Last Weekend". Weather.com. Weather.com. Retrieved 19 June 2019.
  41. ↑ Bates, Becky (19 June 2019). "Rare clockwise-spinning tornado touches down in South Dakota". KTVQ. KTVQ. Retrieved 19 June 2019.
  42. ↑ Smith, Grant. "Rare anticyclonic tornado spotted in Deuel County". KELO. KELO. Retrieved 19 June 2019.
  43. ↑ Storm Events Database July 29, 2021 (Report). National Centers for Environmental Information. National Centers for Environmental Information. Retrieved November 6, 2021.
  44. ↑ Storm Events Database August 27, 2021 (Report). National Centers for Environmental Information. National Centers for Environmental Information. Retrieved November 20, 2021.
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