DATASTREME SUPPLEMENTAL SUMMARY
To complement the Daily Summary for Tuesday, 4 December 2001
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, 2001, The American Meteorological Society.