NASA - National Aeronautics and Space Administration

A hurricane is a big, powerful storm that forms over the ocean. It causes heavy rain, and it has strong, whirling winds. Most hurricanes measure 200 to 300 miles (320 to 480 kilometers) across. Some have winds that blow at speeds of 130 to 200 miles (210 to 320 kilometers) per hour. They can cause much destruction.

Image to right: Hurricane Andrew struck the Bahamas, Florida, and Louisiana in 1992, killing 65 people and causing billions of dollars in damage. Credit: NASA

Hurricanes form in warm areas of the North Atlantic Ocean and the eastern North Pacific Ocean. They can occur from June to November. Most of them strike in August and September. As many as 15 hurricanes occurred in the Atlantic in a single year. In the western North Pacific Ocean, such storms are called typhoons. In the Indian Ocean and near Australia, these storms are called cyclones. Altogether, about 85 hurricanes, typhoons, and cyclones develop each year.

The winds of a hurricane swirl around the eye of the storm, a calm area in its center. The eye of a hurricane has few winds or clouds. It can be clear and sunny in the eye of a storm. Storm clouds called the eyewall surround the eye. The strongest winds and heaviest rain of a hurricane are within the eyewall.

Movement of a Hurricane

In the southern part of the world, hurricane winds blow around the eye in a clockwise direction. This is the same direction that the hands of a clock move around the clock's face. In the northern part of the world, the winds blow counterclockwise, or in the other direction. Hurricanes travel at speeds of 5 to 20 miles (8 to 32 kilometers) per hour. They become larger and stronger as they travel.

Image to left: Hurricane winds swirl around the eye, a calm area in the storm's center. Credit: World Book illustrations by Bruce Kerr

When a hurricane moves over land, strong winds and heavy rain hit the land for several hours. As the eye of the hurricane reaches the area, the rain stops and the air becomes calm. Less than an hour later, the eye passes and the rain and wind return. The hurricane grows weaker as it moves over land. The wind slows down, but heavy rain may continue. Gradually, the hurricane dies out. Many hurricanes die out over cool oceans.

Hurricane Damage

Hurricanes do great damage with their strong winds. They also create huge waves in the ocean that can cause floods. These waves are called a storm surge. In the United States, most hurricanes cause destruction in areas near the Atlantic Ocean or the Gulf of Mexico.

Hurricane Warnings

During the hurricane season in the United States, people who study the weather watch for hurricanes in the Atlantic and Pacific Oceans. When they see a storm developing, they study the size and strength of the storm and the direction the storm is traveling. They use all this information to figure out where the hurricane will hit land and how strong it will be. Television and radio stations then broadcast this information.

How to cite this article: To cite this article, World Book recommends the following format: "Hurricane." The World Book Student Discovery Encyclopedia. Chicago: World Book, Inc., 2005.

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