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    Why Lee Has Spawned Tornadoes

    By By Grace Muller, AccuWeather.com staff writer
    September 08, 2011, 5:08:08 AM EDT

    How come already destructive tropical systems bring down fast moving and hard to pinpoint tornadoes?

    Landfalling tropical cyclones produce one of the key parts needed for tornado formation: wind shear. Wind shear is when winds change speed and direction at different heights in the storm.

    Typically, tornadoes form north and east of the center of the storm. The strongest winds and wind shear are usually there.

    AccuWeather Expert Senior Meteorologist Henry Margusity has a theory of his own on why Lee formed tornadoes: "Some hurricanes cause tornadoes and some don't. It has to do with the amount of tropical moisture associated with the storm."

    "If the dew points are very high, that allows a greater amount of latent heat to be released in the storms," Margusity said. "The heat lowers the pressures in the thunderstorms. With the lower pressure, storms start to rotate in an already highly-sheared environment to produce tornadoes."

    "Also, if you have the higher dew points, the formation of the funnel can occur all the way to the ground level," he added. "So from a forecaster prospective, look for the areas with high dew points, and that's where you will find the tornadoes."

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