Tropical Cyclones

Ever wonder what all those advisories, watches and warnings mean? Well, here they are all organized and described for you. For more details, check out the NHC website Help or FAQ pages.

NHC Advisory	Description
Tropical Wave	A trough of low pressure in the trade-wind easterlies.
Tropical Disturbance	A moving area of thunderstorms in the Tropics that maintains its identity for 24 hours or more. A common phenomenon.
Tropical Depression	An organized system of clouds and thunderstorms with a defined surface circulation and maximum sustained winds* of 38 mph (33 kt**) or less.
Tropical Storm	An organized system of strong thunderstorms with a defined surface circulation and maximum sustained winds of 39-73 mph (34-63 kt).
Hurricane	An intense tropical weather system of strong thunderstorms with a well-defined surface circulation and maximum sustained winds of 74 mph (64 kt) or higher.
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.
Tropical Storm Watch	Issued for a coastal area when there is the threat of tropical storm conditions within 36 hours.
Tropical Storm Warning	A warning for tropical storm conditions including sustained winds within the range of 39 to 73mph (34 to 63 knots) which are expected in a specified area within 24 hours.
Hurricane Watch	An announcement that hurricane conditions pose a possible threat to a specified coastal area within 36 hours.
Hurricane Warning	A warning that sustained winds of 74 mph(64kts) or higher are expected in a specified coastal area within 24 hours.
Storm Surge	An abnormal rise of the sea along a shore as the result, primarily, of the winds of a storm.
Flash Flood Watch	Means that flash flood conditions are possible within the designated watch area.
Flash Flood Warning	Means a flash flood has been reported or is imminent.

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