Stormy Weather

Hurricanes, Monsoons, and Tropical Storms

What is a hurricane?

A hurricane is a tropical storm that has winds of 74 miles per hour or more that forms in the Atlantic Basin. Hurricanes typically occur in the North Atlantic and Caribbean Sea during the months of July, August, and September, when warm surface ocean temperatures exceed 80°F (26.5°C), providing energy that feeds into the storm. Seawater evaporates into the air, creating clouds, while the Coriolis effect causes the clouds to rotate.

For a hurricane to develop, there must not be a lot of difference in wind speeds in the upper and lower elevations of the storm. If there is a big difference in these speeds, the resulting wind sheer will cause the hurricane to become unstable, with clouds and winds opposing each other rather than working together in a gigantic swirl that increases in speed. Hurricanes do not tend to generate close to the equator (within five degrees latitude) because the Coriolis effect is stronger father away from the equator, and also because they need a low pressure area that is not close to the equator.

A space image of 2005’s Hurricane Katrina shows a well-defined, powerful storm system heading for the Gulf Coast. (NASA)

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