File:Hurricane profile graphic-zh.gif

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http://earthobservatory.nasa.gov/Library/Hurricanes/Images/hurricane_section.gif

Hurricanes form when the energy released by the condensation of moisture in rising air causes a chain reaction. The air heats up, rising further, which leads to more condensation. The air flowing out of the top of this “chimney” drops towards the ground, forming powerful winds. (Graphic by Robert Simmon, NASA GSFC)