Why do hurricanes rotate counterclockwise and move from east to west?

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by Evan Stewart

WVEC.com

Posted on March 10, 2010 at 5:44 PM

Updated Tuesday, May 31 at 2:45 PM

Hurricanes spin counterclockwise (like all low pressure centers in the northern hemisphere) because of the Coriolis Effect. Because the equator rotates faster than other areas of the Earth's surface, anything moving in a straight line on a North to South axis will eventually curve. If you could throw a ball hard enough and far enough, it too would eventually curve.

Since air flows into a low pressure center, sort of like water going down a drain, it curves counterclockwise. Conversely, since air flows out of a high pressure center, they rotate clockwise above the equator, and counterclockwise down under.

This phenomenon was first observed by French mathematician Gaspard Coriolis in the early 1800's. The Coriolis effect must also be taken into account when the trajectory of a rocket is calculated.

Hurricanes move from east to west because they are caught up in the trade winds, which blow from east to west near the equator. Once a hurricane moves north of about 30° latitude, they frequently curve, and often do move from west to east, as does most of our other our weather.

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