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By international agreement, tropical cyclone is the general term for all cyclonic circulations originating over tropical waters, classified by form and intensity as follows:
TROPICAL DISTURBANCE: A moving area of thunderstorms in the tropics that maintains its identity for 24 hours or more. A common phenomenon in the tropics.
TROPICAL DEPRESSION: Rotary circulation, sustained wind speed 38 miles per hour (33 knots) or less.
TROPICAL STORM: Distinct rotary circulation, sustained wind speed range of 39-73 miles per hour (34-63 knots).
HURRICANE: Pronounced rotary circulation, sustained wind speed of 74 miles per hour (64 knots) or more.
SMALL CRAFT CAUTIONARY STATEMENTS. When a tropical cyclone threatens a coastal area, small craft operators are advised to remain in port or not to venture into the open sea.
GALE WARNINGS are issued when winds of 39-54 miles an hour (34-47 knots) are expected.
STORM WARNINGS are issued when winds of 55-73 miles and hour (48-63 knots) are expected.
A HURRICANE WATCH is issued when there is a threat of hurricane conditions within 48 hours. Preliminary precautions should be taken.
A HURRICANE WARNING is issued when sustained winds of 74 mph or more are expected in a specified area in 36 hours or less. A hurricane warning can remain in effect when dangerously high water or high waves continue, even though winds may be less than 74 mph. Actions for protection of life and property should begin immediately when the warning is issued.
FLASH FLOOD WATCH means a flash flood is possible in the area; stay alert.
FLASH FLOOD WARNING means a flash flood is imminent or occurring; take immediate action.
TORNADOES spawned by hurricanes sometimes produce severe damage and casualties. If a tornado is reported in your area, a warning will be issued.
|Last Reviewed: Tuesday, July 12, 2011|