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Earth Sense: Hurricanes move excess heat from tropics
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Hurricanes aren’t entirely bad. Like their weaker cousins, the tropical storms, they have a job assigned by nature. In North Georgia, we saw this last week when storm bands from Tropical Storm Cindy spread generous rain over the Gainesville area.

The job of systems like Cindy is to move excess heat away from the tropics. In our hemisphere, at latitudes between Cuba and the equator (23.5 to 0 degrees), winter season is warm or nonexistent.

Ocean water can, and does, store a lot of heat. And since there’s more heat coming in than going back out into space, it needs to be distributed somehow.

Currently, the sea temperature at Havana, Cuba, is 84 degrees. That’s expected to rise some more because summer is less than two weeks old. All the way to Africa across the Atlantic, the temperatures are similar.

Moisture put in the air by those warm waters builds clouds. Gradually, some localized rainstorms combine, and the earth’s rotation causes big clusters of storms to rotate. Once the inside wind speed exceeds 38 mph, a tropical storm is born.

Now the surface windflow, going from east to west in the tropics, pushes the system toward the Caribbean. Dad’s old fishing boat with its aging outboard engine could keep up with the movement of a tropical storm, even a hurricane. They move at just 10 to 15 mph.

Storms that reach land (“make landfall”) on the Gulf Coast, like Cindy did on June 22, get dragged northeastward by the airflow that dominates our continent. For North Georgia, this meant thunderstorms and rain, and some flash flooding in low-lying areas of the Chattahoochee Valley. The effect on Lake Lanier’s water level, and the vegetation cover in the region, was beneficial.

It’s a different story on the coast, where towns don’t have the advantage of elevation and fast runoff. Parts of Mississippi and Louisiana experienced dangerous flooding.

In Alabama, a young boy was killed by debris thrown out by the waves. With nothing but sand in front and below them, houses at and near the beach remain the most vulnerable to impact damage from the storm’s waves.

In the flat coastal plain, the hazard is in being submerged under floodwaters. Watching the most recent news videos of last-second rescues of motorists and residents should convince anyone to take flash flood warnings seriously.

Rudi Kiefer, Ph.D., is a professor of physical science and director of sustainability at Brenau University. His column appears Sundays and at

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