Hurricanes are a category of tropical cyclone. A tropical cyclone is a circulating weather system with low pressure over tropical water. It forms when warm ocean water begins to evaporate and warms and moistens the air above it. As the air rises it begins to circulate, counterclockwise in the Northern Hemisphere, around a low-pressure area. When the winds of a tropical cyclone are sustained at 74 miles per hour or more, the system is called a hurricane.
A hurricane system may extend 400 miles across, with winds of more than 155 miles per hour. The area of low pressure around which the air circulates in a hurricane is called the eye. The eye of a hurricane can be 20 to 30 miles across. The air in this area is calm. When the eye passes over an area of land, the winds die down and the calm may last from a few minutes to a few hours. However, the other half of the hurricane is behind the eye, and the winds are strong and blow in the opposite direction.
When and Where Do Hurricanes Form?
Hurricanes most often affect the Atlantic and Gulf coasts of North America, the islands of the Caribbean and the tropical areas of the West Pacific. They form mostly over waters between 5 and 30 degrees latitude north and south of the equator. In the Atlantic Ocean and Caribbean Sea, hurricanes form during "hurricane season," which is June 1 through November 30. Approximately six hurricanes form in the North Atlantic each year. One or two of these will hit the United States.
What Are the Consequences of Hurricanes?
Hurricane winds can be very destructive. Property can be destroyed by the strength of the winds and by flying debris. Power lines may be knocked down, and water, sewage and gas systems may be damaged. Many times injuries and deaths also result from flying debris.
The winds of a hurricane can cause a storm surge, a wall of ocean water, that can reach 20 feet high and over 50 miles wide. When the storm surge reaches land, it can destroy property and kill those in its path. In addition, hurricanes are known to cause tornadoes, fires and floods. In fact, most hurricane fatalities are related to flooding. All of these events can also lead to injuries and disease from hypothermia, water and food contamination, and unsanitary conditions.
Resources for Hurricanes