Anticyclonic tornado

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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]

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

Formation[edit]

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[edit]

Date Location Notes and References
08 June 1951 Corn, Oklahoma First known tornado filmed in the US, a companion or cyclic tornado to another significant tornado
06 June 1975 Freedom, Oklahoma [5] [6]
13 June 1976 Central Iowa [7]
06 April 1980 Grand Island, Nebraska [8]
04 April 1981 West Bend, Wisconsin 1981 West Bend F4 anticyclonic tornado
04 May 1998 San Francisco Bay Area, California [4]
19 April 2002 Lubbock, Texas
06 September 2004 Chek-Lap-Kok International Airport, Hong Kong, China [9]
24 April 2006 El Reno, Oklahoma [2]
20 June 2006 Rushville, Nebraska
10 May 2010 South-central Oklahoma Two tornadoes associated with anticyclonic supercell[10]
31 May 2013 El Reno, Oklahoma
04 June 2015 Elbert County, Colorado [11]
05 April 2017 Shelbyville, Tennessee [12]
05 January 2019 Seymour, Texas Two possible and confirmation coming[citation needed]

See also[edit]

References[edit]

  1. ^ Edwards, Roger. "The Online Tornado FAQ". NWS Storm Prediction Center. Retrieved 2019-05-02.
  2. ^ 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.
  3. ^ Stull, Roland B. (2000). Meteorology for Scientists and Engineers (2nd ed.). Thomson Learning. ISBN 9780534372149.
  4. ^ 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.
  5. ^ "Freedom, Oklahoma Anticyclonic Tornado - June 6, 1975". Youtube. cyclonejimcom. Retrieved 9 April 2019.
  6. ^ Grazulis, Thomas P. "Twister: Fury on the Plains (1995)". imdb. Music Video Productions (co-production); The Tornado Project. Retrieved 9 April 2019.
  7. ^ 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. doi:10.1175/1520-0493(1980)108<1626:TICATP>2.0.CO;2.
  8. ^ 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.
  9. ^ Kosiba, Karen A.; Robinson, Paul; Chan, P. W.; Wurman, Joshua (2014). "Wind Field of a Nonmesocyclone Anticyclonic Tornado Crossing the Hong Kong International Airport". 2014 (597378). Hindawi. doi:10.1155/2014/597378.
  10. ^ "The May 10, 2010 Tornado Outbreak in Oklahoma". National Weather Service Forecast Office - Norman, Oklahoma. 2010. Retrieved 2019-05-02.
  11. ^ "Storm Damage Surveys for June 4th Tornadoes". Denver/Boulder, CO Weather Forecast Office. Retrieved 10 April 2019.
  12. ^ Edwards, Christina. "A "very unique event": Rare anticyclonic tornado touched down in southeastern Tennessee Wednesday". WHNT News (Channel 9 FOX). Retrieved 10 April 2019.

External links[edit]