A small craft advisory is a type of warning issued by the National Weather Service in the United States, most frequently in coastal areas. It is issued when winds have reached, or are expected to reach within 12 hours, a speed marginally less than gale force.
The term wind advisory is used in place of small craft advisory when winds of the same force occur at, or are forecast for, inland locations. A lake wind advisory is issued for winds just below this range, because unobstructed winds across the open waters of a lake are normally faster than across land.
The wind speed that triggers the advisory has changed over time. Until the late 1960s, the threshold was 32 to 38 miles per hour (or 28 to 33 knots). At some point, the lower limit was reduced to 23 miles per hour (20 knots). Today, however, most places have standardized on 25 to 38 miles per hour (22 to 33 knots), encompassing the combined ranges of forces 6 and 7 on the Beaufort scale.
Occasionally an informal lesser advisory, known as "small craft exercise caution," is issued for wind speeds lighter than those that call for a small craft advisory. Criteria for this vary in different localities; sometimes a range of 19 to 24 miles per hour (17 to 21 knots) is observed, or in some places 17 to 23 miles per hour (15 to 19 knots) may be used.
The insignia that denotes a small craft advisory is one red, triangular flag (two such flags, one placed above the other, signify a gale warning).
The National Weather Service does not specifically identify what constitutes a "small craft," although the United States Coast Guard informally assigns the designation to boats with a total length of less than 33 feet (10 m).
The next step above these advisories is a high wind warning. All such bulletins may also be issued for areas above a particular elevation, as wind speeds tend to increase with altitude in the mountains.
As of February 15, 1989, the National Weather Service retired its Coastal Warning Display network nationwide.
For over 100 years, display stations were established at yacht clubs, marinas, and Coast Guard stations to hoist flags, pennants and colored lights to warn mariners of storms at sea. The display stations were individually notified by the National Weather Service to raise the signals and again to lower them when the hazards passed. The National Weather Service paid for the visual signals; however, the display stations were operated by other agencies or volunteers. Although the Coastal Warning Display program has been formally discontinued, U.S. Coast Guard and other stations may continue to display warning signals without the direct participation of the National Weather Service.
Beginning June 1, 2007, U.S. Coast Guard formally re-established a Coastal Warning Display program at selected small boat stations which will hoist display flags to warn of small craft advisories, gale warnings, storm warnings and hurricane warnings.
The Coastal Warning Display program was de-emphasized in favor of frequently updated telephone recordings and NOAA Weather Radio. The latter covers the coastal areas of continental United States, Alaska, Hawaii, and the Mariana Islands with continuous weather broadcasts. The major shortcomings of the Coastal Warning Display program were that the displays reached only the small portion of the marine public within sight of them; it cannot convey specific information on movement, intensity, and duration; and the time required to notify the sites by individual telephone calls takes the forecaster away from critical tasks associated with the weather. Further, when users perceive them to be a full substitute for NOAA Weather Radio, other radio broadcasts, and the telephone recordings, they are actually being a disservice.
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A similar warning, known as a Strong Wind Warning, is issued by Environment Canada's Meteorological Service of Canada from its different offices for the Pacific, Atlantic, and Arctic waters. These warnings are coordinated for the Great Lakes region with American neighboring offices.
URGENT - MARINE WEATHER MESSAGE NATIONAL WEATHER SERVICE BUFFALO NY 1015 AM EDT SAT OCT 18 2008 LAKE ONTARIO NEARSHORE WATERS FROM THE NIAGARA RIVER TO HAMLIN BEACH- LAKE ONTARIO NEARSHORE WATERS FROM HAMLIN BEACH TO SODUS BAY- 1015 AM EDT SAT OCT 18 2008 ...SMALL CRAFT ADVISORY NOW IN EFFECT UNTIL 4 PM EDT THIS AFTERNOON... THE SMALL CRAFT ADVISORY IS NOW IN EFFECT UNTIL 4 PM EDT THIS AFTERNOON. NORTHEAST WINS OF 15 TO 20 KNOTS WILL RESULT IN WAVES OF 3 TO 5 FEET THROUGH EARLY AFTERNOON...THEN DECREASE TO 1 TO 3 FEET THIS EVENING AS WINDS DIMINISH. PRECAUTIONARY/PREPAREDNESS ACTIONS... A SMALL CRAFT ADVISORY MEANS WINDS WILL PRODUCE WAVES 4 FEET OR HIGHER. THIS WILL BE HAZARDOUS FOR SMALL CRAFT. INEXPERIENCED MARINERS... ESPECIALLY THOSE OPERATING SMALLER VESSELS... SHOULD AVOID NAVIGATING IN THESE CONDITIONS.
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