Tropical
Weather Glossary
June,
2000
Prepared by PLRB
Catastrophe Services
Materials provided by National Oceanic and Atmospheric Administration (NOAA)
and the National Weather Service (NWS)
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. It is a common phenomenon in
the tropics.
Tropical Cyclone - A generic term for a non-frontal low pressure system
with organized convection and a cyclonic wind circulation. It forms where the
ocean's water temperature exceeds 80° F.
Tropical Depression - A tropical cyclone in which the maximum sustained
surface wind is 38 MPH (33 knots) or less.
Tropical Storm - A tropical cyclone in which the maximum sustained
surface wind ranges from 39 to 73 MPH (34 to 63 knots) inclusive.
Hurricane - A tropical cyclone in which maximum sustained surface wind
is 74 MPH (64 MPH) or greater.
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 - Is issued for a coastal area when there is a threat
of tropical storm conditions within 36 hours.
Tropical Storm Warning - A warning for tropical storm conditions,
including sustained high winds within the range of 39 to 73 MPH (34 to 63
knots) which are expected in a specified coastal area within 36 hours.
Hurricane Watch - An announcement that hurricane conditions post a
possible threat to a specified coastal area within 36 hours.
Hurricane Warning - A warning that sustained winds of 74 MPH (64 knots)
or higher are expected in a specified coastal area within 24 hours or less.
Landfall – When the surface center, or eye, of a hurricane intersects
with a coastline.
Storm Surge - An abnormal rise of the sea along a shore as the result,
primarily, of the winds in a storm.
Flash Flood Watch - Flash flood conditions are possible within a
designated watch area.
Flash Flood Warning - A flash flood has been reported or is imminent.
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