Do all tornadoes rotate the same way?


Do all tornadoes spin/turn the same way?

– Chris Jensen, Sioux Falls

Dear Chris,

In meteorology we use the terms cyclonic and anti-cyclonic. A low pressure system is considered a cyclone, which spins counterclockwise, while a high pressure system is a anticyclone, which spins clockwise. See the picture below for a visual demonstration. (In the Southern Hemisphere it is the opposite. Cyclone = Clockwise & Anticylone = Counterclockwise)

Just imagine a tornado as a very small cyclone. Most tornadoes in the Northern Hemisphere rotate/turn “cyclonically,” counterclockwise. Tornadoes that occur in the Southern Hemisphere still turn “cyclonically” as well, but south of the equator, cyclonic storms rotate clockwise.

The most dangerous tornadoes form underneath a wall cloud, which in turn forms underneath a mesocyclone (There’s that cyclone word again). The definition of a mesocyclone is a vortex of air within a convective storm, or a smaller cyclone. Again, cyclones spin counterclockwise. Since the rotation in these storms is already counterclockwise, air that is rotated to the ground will also move counterclockwise.

However, there have been sightings of anticyclonic tornadoes! An anticyclonic tornado spins clockwise in the Northern Hemisphere, and vice versa in the Southern Hemisphere. The usually are in the form of waterspouts, non-supercell land tornadoes, or anticyclonic whirls around the rim of a supercell’s mesocyclone, which are very tame tornadoes. However, there have been a couple documented anticyclonic supercells which featured an clockwise rotating tornado, but they are extremely rare! Hope that helped answer you question!

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