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Weekend


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October 31, 2003

Strange But True!

  • A weekly column of incidental information, off-the-wall observations and other random facts about the world.
    • By BILL SONES and RICH SONES, Ph.D.
    Special to the Journal

    Q. From a Peoria, Illinois reader: Do all tornadoes in the Northern hemisphere spin one direction while those in the Southern hemisphere spin the other way? If so, would a tornado stop when it got to the equator?

    A. Tornadoes are small enough that they can spin either way in either hemisphere and they are observed to do just that, says University of Hawaii meteorologist Steven Businger. An estimated 90 percent to 97 percent, however, do twist counterclockwise in the Northern hemisphere (as seen from above) as a result of how spawning storms form. A tornado can form near the equator and cross it, though tornadic conditions are not common there. Larger storms, such as hurricanes, only spin one way in each hemisphere due to the Earth's rotation and they cannot and do not cross the equator. "Advection of vorticity makes hurricanes curve away from the equator."


     
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