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Decipher those hurricane terms

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(CNN) -- What's the difference between a warning and a watch? What exactly is a cyclone? Check out some of the hurricane-related terminology, according to the National Hurricane Center:

An atmospheric closed circulation, rotating counterclockwise in the Northern Hemisphere and clockwise in the Southern Hemisphere.

The roughly circular area of comparatively light winds that encompasses the center of a severe tropical cyclone. The eye is either completely or partially (at least 50 percent) surrounded by the eye-wall cloud, an organized band or ring of cumulonimbus clouds.

A tropical cyclone in which the maximum sustained surface wind is 74 mph (118 kmh) or more. The term "hurricane" is used for Northern Hemisphere cyclones east of the International Dateline to the Greenwich Meridian. The term "typhoon" is used for Pacific cyclones north of the Equator west of the International Dateline.

Hurricane season
The part of the year having a relatively high incidence of hurricanes. The hurricane season in the Atlantic, Caribbean and Gulf of Mexico runs from June 1 to November 30. The season in the Eastern Pacific basin runs from May 15 to November 30. The season in the Central Pacific basin runs from June 1 to November 30.

Hurricane warning
A warning that sustained winds of 74 mph (118 kmh) or higher associated with a hurricane are expected in a specified coastal area within 24 hours. A hurricane warning can remain in effect when dangerously high water or waves continue, even though winds may be less than hurricane force.

Hurricane watch
An announcement of specific coastal areas in which a hurricane poses a possible threat, generally within 36 hours.

Landfall occurs when the edge of the eye of a hurricane (or lesser tropical cyclone) reaches land. Since the strongest winds are not directly in the center, it is possible for the strongest winds to be felt before or after landfall or for them to be over water at landfall.

Saffir-Simpson Scale
The Saffir-Simpson Hurricane Scale is a 1-5 rating based on the hurricane's present intensity. It is used to give an estimate of the potential property damage and flooding expected along the coast from a hurricane landfall. Wind speed is the determining factor in the scale.

Storm surge
An abnormal rise in sea level accompanying a hurricane or other intense storm, the height of which is the difference between the observed level of the sea surface and the level that would have occurred in the absence of the cyclone. Storm surge is usually estimated by subtracting the normal or astronomic high tide from the observed storm tide. The storm tide is the actual level of sea water resulting from the astronomic tide combined with the storm surge.

Tropical storm
A tropical cyclone in which the maximum sustained surface wind speed ranges from 39 mph to 73 mph (62.4 kmh to 116 kmh). E-mail to a friend E-mail to a friend

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