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. It is simply a naming convention denoting the anomaly from normal rotation which is cyclonic in upwards of 99 percent of tornadoes. Usually, however, anticyclonic tornadoes are smaller and weaker than classic tornadoes, forming from a different process.

Most strong tornadoes (the classic conception of a tornado) form in the inflow and updraft area bordering the updraft-downdraft interchange 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 the smaller rotation that is a tornado. All of these may be, but aren't always, vertically connected 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. 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. Various processes can produce an anticyclonic tornado. Most often (but various other forms and causes exist) they are satellite tornadoes of larger tornadoes which are directly associated with the tornadocyclone and mesocyclone.

Anticyclonic tornado

See also