John Wheeler, WDAY, Published June 15 2013
Weather Talk: An anticyclonic tornado accompanied huge Oklahoma oneThe huge and destructive EF5 tornado that hit El Reno, Okla., a couple of weeks ago was accompanied by a less common, anticyclonic tornado three miles to the southeast.
The direction of spin in a tornado is derived from the parent mesocyclone, which is large enough to be affected by the Coriolis Force, an artifact of Earth’s rotation. Smaller vortices, such as cold air funnels, waterspouts and the little tornadoes above the bathtub drain, are too small and can spin in either direction.
However, most tornadoes spin counterclockwise. The sister tornado to the primary El Reno tornado was caused by a counterclockwise eddy, resulting in a tornado with this backward spin.
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