Hot tower

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Hot Tower in Hurricane Bonnie 1998. Altitude of clouds are exaggerated

The "hot tower hypothesis" was proposed in 1958 by Joanne Malkus Simpson and Herbert Riehl. Prior to 1958, the mechanism driving the global-scale circulation pattern called Hadley cells was poorly understood. Simpson and Riehl proposed that the energy feeding these enormous convective cells was supplied by the release of latent heat during condensation of warm, moist air in the centers of tropical storms, including hurricanes.

A "hot tower" is a tropical cumulonimbus cloud that penetrates the tropopause, i.e. it reaches out of the lowest layer of the atmosphere, the troposphere, into the stratosphere. In the tropics, the tropopause typically lies at least 15 km above sea level. These towers are called "hot" because they rise high due to the large amount of latent heat released as water vapor condenses into liquid.

Recently the National Aeronautics and Space Administration (NASA) has discovered that these hot towers appear when the hurricane is about to intensify. A particularly tall hot tower rose above Hurricane Bonnie in August 1998, as the storm intensified before striking North Carolina, United States. Bonnie caused more than $1 billion damage and three deaths, according to the National Oceanic and Atmospheric Administration and the National Hurricane Center.