To complement the Daily Summary for Tuesday, 27 April 1999
SPECIFIC TROPICAL & MARINE STATEMENT TERMINOLOGY
The National Weather Service issues various marine-related advisories,
watches and warnings to the public that pertain to a variety of
severe weather conditions as well as unusual water, waves and
current conditions that could affect life and property. The area
of responsibility includes the coastal waters and the open waters
of the Atlantic and Pacific Oceans and the Gulf of Mexico. Some
of these statements cover tropical weather systems, including
tropical storms and hurricanes. The National Hurricane Center
(NHC) in Miami, FL, a part of the Tropical Prediction Center,
is responsible for issuing statements for the North Atlantic Basin
(to include the Gulf of Mexico and the Caribbean Sea) and the
eastern Pacific Basin (to 140 degrees West longitude). The Pacific
Hurricane Center in Honolulu, HI monitors the Central Pacific
to the International Date Line (at 180 degrees). The Hawaiian
Islands are found within this region. The Marine Prediction Center
(MPC), another component of the National Centers for Environmental
Prediction issues marine warnings for situations not involving
tropical weather systems.
The following list includes terminology used by the National Weather
Service for those public statements pertaining to tropical weather:
- Tropical storm watch -- Issued by the National Hurricane
Center to alert the public in a coastal area when a threat of
tropical storm conditions (sustained winds within the range 34
to 63 knots) is predicted within 36 hours.
- Tropical storm warning -- Issued to warn the public
of imminent tropical storm conditions (sustained winds within
the range 34-63 knots), which are expected in a specified coastal
area within 24 hours or less.
- Hurricane watch -- Issued by the National Hurricane
Center for specific areas that an incipient hurricane condition
poses a possible threat to coastal areas generally within 36 hours.
The public should be prepared to take precautionary action if
a hurricane warning were issued.
- Hurricane warning -- Issued to warn the public that
1-minute sustained surface winds of 64 knots (74 mph) or higher
associated with a hurricane are expected in a specified coastal
area within 24 hours or less. A hurricane warning can remain in
effect when dangerously high water and exceptionally high waves
continue even though winds may be less than hurricane force. The
public should take immediate action.
The following statements can be issued for several types of events,
not limited to tropical weather systems:
- Coastal flood watch -- Issued to alert coastal residents
of the possibility of the inundation of land areas along the coast
within the next 12 to 36 hours.
- Coastal flood warning -- Issued to warn residents of
coastal areas that land areas along the coast will be inundated
by sea water above the typical tide action.
- Heavy surf advisory -- Issued to inform the public
that high ocean surf may pose a threat to life or property.
- Tsunami watch/warning -- Issued by the National Weather
Service to either alert or warn residents in regions along the
Pacific Ocean that an impending tsunami (seismic sea wave) may
cause damage to low lying regions. The type of bulletin is based
on the magnitude and the location of the underwater geological
event. The content and format are similar to coastal flood watches
and warnings.
The following marine weather statements can be issued:
- Small-craft advisory -- Issued to advise mariners of
sustained (exceeding two hours) weather and/or sea conditions,
either present or forecast, potentially hazardous to small boats.
These conditions generally include winds of 18-33 knots and/or
dangerous wave conditions. Small craft advisories may be issued
also for hazardous sea conditions or lower wind speeds that may
affect small craft operations. Advisories can be issued up to
12 hours prior to the onset of adverse conditions.
- Small-craft warning -- Issued as a warning, for marine
interests, of impending winds up to 28 knots (32 mph); used mostly
in coastal or inland waters.
- Gale warning -- A storm warning, for marine interests,
of impending winds from 34 to 47 knots (39 to 54 mph). The storm
warning signals for this condition are (a) two triangular red
pennants by day, and (b) a white lantern over a red lantern by
night.
- Whole-gale warning -- A warning, for marine interests,
of impending winds of 48-63 knots (55-72 mph). The storm-warning
signals for this condition are (a) one square red flag with black
center by day and (b) two red lanterns by night.
The National Hurricane Center (Tropical Prediction Center) issues
Tropical Weather Outlooks. The information contained in
these guidance products are used on television weather casts.
These Outlooks include levels of risk.
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Prepared by Edward J. Hopkins, Ph.D., email hopkins@meteor.wisc.edu
© Copyright, 1999, The American Meteorological Society.