Small craft advisory
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A small craft advisory is a type of wind warning issued by the National Weather Service in the United States. In Canada a similar warning is issued by Environment Canada. It is issued when winds have reached, or are expected to reach within 12 hours, a speed marginally less than gale force. A Small Craft Advisory may also be issued when sea or lake ice exists that could be hazardous to small boats.[1]
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).
Inland, this advisory is known as a wind advisory. 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. Winds strong enough to trigger a small craft advisory may be referred to as being "advisory-force". Conversely, winds just above this intensity (39–57 miles per hour) are called "gale-force", and have a separate associated warning.
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 National Weather Service does not specifically identify what constitutes a "small craft". The size of the boat is only part of what a person should consider when venturing out under such a warning. Weight, displacement and hull design are also important factors and an even more important consideration is not only the craft, but the experience of the captain.
The next step above these advisories is a gale warning, known as a high wind warning when issued for inland locations. If the winds are associated with a tropical cyclone, then the next level above a small craft or wind advisory is a tropical storm warning. Occasionally, such bulletins may also be issued for areas above a particular elevation, as wind speeds tend to increase with altitude in the mountains.
Coastal Warning Display program
[edit]As of 15 February 1989, the National Weather Service retired its Coastal Warning Display network nationwide.[2]
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 1 June 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, tropical storm warnings, storm warnings, hurricane warnings, and hurricane-force wind warnings.[3]
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.
Canada
[edit]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.
Strong Wind Warning was previously referred to as Small Craft Warning and is still (2012) referred to as such in many publications. A Strong Wind Warning is issued for winds in the range 20–33 knots and wave heights 2–3 metres.
Example of Small Craft Advisory
[edit]This is an example of a Small Craft Advisory from the National Weather Service Forecast Office in Los Angeles, California.[4]
URGENT - MARINE WEATHER MESSAGE NATIONAL WEATHER SERVICE LOS ANGELES/OXNARD CA 906 PM PDT FRI MAR 16 2012 PZZ670-171215- /O.NEW.KLOX.SC.Y.0036.120317T0406Z-120317T1600Z/ /O.EXB.KLOX.GL.W.0016.120317T2200Z-120319T1000Z/ /O.UPG.KLOX.GL.A.0010.120318T0000Z-120319T1000Z/ WATERS FROM PT. PIEDRAS BLANCAS TO PT. ARGUELLO AND WESTWARD 60 NM- 906 PM PDT FRI MAR 16 2012 ...SMALL CRAFT ADVISORY IN EFFECT UNTIL 9 AM PDT SATURDAY... ...GALE WARNING IN EFFECT FROM 3 PM SATURDAY TO 3 AM PDT MONDAY... THE NATIONAL WEATHER SERVICE IN LOS ANGELES/OXNARD HAS ISSUED A GALE WARNING FOR THE WATERS FROM POINT PIEDRAS BLANCAS TO POINT ARGUELLO AND WESTWARD 60 NM. THIS WARNING IS IN EFFECT FROM 3 PM SATURDAY TO 3 AM PDT MONDAY. A SMALL CRAFT ADVISORY HAS ALSO BEEN ISSUED. THIS SMALL CRAFT ADVISORY IS IN EFFECT UNTIL 9 AM PDT SATURDAY. THE GALE WATCH IS NO LONGER IN EFFECT. * WINDS...SOUTHWEST WINDS WILL INCREASE TO 10 TO 20 KNOTS WITH FREQUENT GUSTS TO 25 KNOTS TONIGHT AND CONTINUE THROUGH SATURDAY MORNING. THE WINDS WILL THEN SHIFT TO NORTHWEST AND INCREASE THROUGH SATURDAY AFTERNOON. NORTHWEST WINDS 15 TO 25 KNOTS WITH FREQUENT GUSTS BETWEEN 35 AND 40 KNOTS WILL DEVELOP LATE SATURDAY AFTERNOON AND CONTINUE INTO SUNDAY EVENING. THE WINDS WILL BEGIN TO DIMINISH LATE SUNDAY NIGHT. * SEAS...SHORT-PERIOD AND STEEP HAZARDOUS SEAS BETWEEN 10 AND 12 FEET WILL DEVELOP SATURDAY AFTERNOON...THEN BUILD TO BETWEEN 15 AND 20 FEET SATURDAY NIGHT INTO SUNDAY. PRECAUTIONARY/PREPAREDNESS ACTIONS... A GALE WARNING MEANS WINDS OF 34 TO 47 KNOTS ARE IMMINENT OR OCCURRING. OPERATING A VESSEL IN GALE CONDITIONS REQUIRES EXPERIENCE AND PROPERLY EQUIPPED VESSELS. IT IS HIGHLY RECOMMENDED THAT MARINERS WITHOUT THE PROPER EXPERIENCE SEEK SAFE HARBOR PRIOR TO THE ONSET OF GALE CONDITIONS. A SMALL CRAFT ADVISORY MEANS THAT WIND SPEEDS OF 21 TO 33 KNOTS ARE EXPECTED TO PRODUCE HAZARDOUS WAVE CONDITIONS TO SMALL CRAFT. INEXPERIENCED MARINERS...ESPECIALLY THOSE OPERATING SMALLER VESSELS SHOULD AVOID NAVIGATING IN THESE CONDITIONS.
See also
[edit]References
[edit]- ^ "Small Craft Advisory Definition". NWS. Retrieved 28 September 2013.
- ^ "COASTAL WARNING DISPLAY PROGRAM". NWS. Retrieved 28 September 2013.
- ^ "COAST GUARD RE-ESTABLISHES STORM FLAG PROGRAM" (PDF). USCG. Retrieved 28 September 2013.
- ^ "Small Craft Advisory". National Weather Service Forecast Office Los Angeles/Oxnard, California. NOAA. Archived from the original on 26 March 2015. Retrieved 17 March 2012.
External links
[edit]Small craft advisory
View on GrokipediaDefinition and Purpose
Core Definition
A small craft advisory is a type of marine weather alert issued by the National Weather Service (NWS) when conditions are expected to become hazardous for smaller vessels, typically involving sustained winds of 20 to 33 knots (23 to 38 mph) or significant wave heights of 4 to 10 feet or more, depending on the region, that could lead to rough seas or difficult handling.[5] This advisory specifically targets operators of small craft, defined broadly as any waterborne vessel likely to be adversely affected by these criteria, including considerations of the boat's size, type, seaworthiness, and the operator's experience.[5] There is no fixed legal definition for small craft, but the term generally applies to recreational boats, fishing vessels, and other watercraft under 33 feet in length, which lack the stability and power of larger ships to navigate such weather safely.[3] In contrast to larger commercial vessels designed to withstand moderate winds and waves, small craft are more vulnerable to capsizing, swamping, or structural damage under these conditions, prompting the advisory to urge caution, preparation, or avoidance of waterways.[4] The advisory forms a key component of the NWS's marine warning system, which provides tiered alerts to protect maritime safety by escalating from advisories for marginal hazards to warnings for more severe threats like gales or storms.[6] The terminology "small craft" traces its roots to traditional nautical usage, where it described compact boats—often tenders or auxiliaries carried aboard larger ships for utility, rescue, or short-distance travel—distinguishing them from substantial sailing or steam vessels. Over time, this evolved in 20th-century meteorological contexts to encompass a wider range of modest-sized pleasure and work boats in weather advisories, reflecting the growing prevalence of recreational boating and the need for tailored safety guidance.Objectives and Safety Implications
The primary objective of a small craft advisory is to alert operators of small vessels to potentially hazardous marine conditions, such as sustained winds or significant wave heights, thereby enabling them to take preventive actions that reduce the risk of accidents, injuries, and fatalities.[6] Issued by meteorological services like the National Weather Service, these advisories aim to promote situational awareness among mariners whose boats may be particularly vulnerable due to size, design, or seaworthiness, ultimately contributing to overall maritime risk mitigation.[6] Safety statistics underscore the critical role of such advisories in addressing weather-related threats, which remain a notable factor in recreational boating incidents despite comprising a relatively small overall percentage. According to the U.S. Coast Guard's 2024 Recreational Boating Statistics report, weather was a contributing factor in 188 accidents, resulting in 55 deaths and 53 injuries out of 3,887 total incidents nationwide.[7] Small craft, typically defined as vessels under 26 feet in length, are involved in over 80% of fatal recreational boating accidents, highlighting their heightened susceptibility to wind and wave hazards that trigger these advisories.[7] The safety implications extend across diverse user groups, tailoring the advisory's value to specific operational contexts. For recreational boaters, who represent the majority of small craft users, advisories encourage postponing outings or equipping vessels with additional safety measures, directly lowering exposure to capsizing or swamping risks.[6] Commercial fishers, often operating smaller inshore vessels, rely on these warnings to assess storm avoidance, as studies show they adjust fishing decisions to minimize threats from rough seas, preserving both crew safety and gear integrity.[8] In search-and-rescue operations, advisories inform planning by signaling conditions hazardous to response craft, allowing coordinators to deploy appropriate resources or delay missions to avoid compounding risks.[6]Issuance Criteria
General Thresholds
A small craft advisory is typically triggered by sustained wind speeds of 20 to 33 knots or by frequent gusts meeting regional thresholds, conditions that can generate hazardous sea states for small vessels.[9] These wind thresholds are designed to alert operators when forces strong enough to challenge stability and maneuverability are imminent, often leading to rough waters even in protected areas.[3] In addition to wind, wave and sea state thresholds play a critical role, with advisories issued for significant wave heights or combined seas reaching 4 feet (1.2 meters) or greater, varying by region, which pose risks of swamping or capsizing small craft.[9] These heights represent the average of the highest one-third of waves, providing a measure of overall sea roughness that impacts vessel safety beyond mere wind influence.[10] The conditions must generally be expected to persist for more than 2 hours to warrant an advisory, focusing on impacts over open or nearshore waters where small craft are most vulnerable.[9] This duration ensures the warning addresses sustained hazards rather than transient events, allowing operators time to seek shelter. Beyond isolated wind or wave metrics, issuance considers combined environmental factors such as reduced visibility, strong currents, or interactive effects like wind opposing the tidal current, which can amplify wave steepness and overall danger to small craft.[11] These elements are evaluated holistically in marine forecasts to provide comprehensive safety guidance for recreational and commercial small vessel operations. In the United States, criteria are defined in National Weather Service Instruction (NWSI) 10-303 and adapted regionally to account for local geography.[9]Regional Variations in Criteria
Small craft advisory criteria are adapted to account for differences in water body types, with lower wind and wave thresholds often applied to inland lakes and protected waters compared to open oceans. For instance, in the Great Lakes, which function as large inland bodies, advisories are typically issued for sustained winds of 22 to 33 knots or waves exceeding 4 feet, reflecting the rapid wave development in shallower, enclosed environments.[6] In contrast, oceanic coastal areas generally require higher thresholds, such as sustained winds of 20 to 33 knots and seas of 7 feet or greater in southern U.S. regions like the Gulf of Mexico, where broader fetches allow for larger but slower-building waves.[6] These variations ensure that advisories align with the specific hazards posed to small vessels in each setting, prioritizing safety in areas with limited maneuverability. Local geography significantly influences criteria, leading to stricter standards in regions prone to amplified conditions from currents, bathymetry, or confinement. In the Great Lakes, the combination of prevailing winds and underwater topography can generate hazardous waves more quickly than in open seas, justifying wave thresholds as low as 4 feet for advisory issuance.[6] Similarly, the Gulf of Mexico's shallow shelf and frequent tropical influences result in advisories for seas of 7 feet or more, as these conditions can rapidly become dangerous for small craft due to the region's variable currents and storm surges.[6] Such adjustments prevent underestimation of risks in geographically constrained or dynamically active waters. While explicit seasonal adjustments to thresholds are not standardized, criteria in tropical and subtropical areas like the southern U.S. coasts incorporate lower wind onset levels (e.g., 20 knots) to address the prevalence of steady trade winds and recurrent convective activity, which normalize higher baseline conditions year-round.[6]| Region Type | Wind Threshold (knots) | Sea/Wave Threshold (feet) | Rationale |
|---|---|---|---|
| U.S. Coastal (e.g., Southern/Gulf of Mexico) | 20-33 | ≥7 | Accommodates open-water exposure and frequent tropical influences, where larger seas develop over extended fetches.[6] |
| U.S. Inland (e.g., Great Lakes) | 22-33 | >4 | Accounts for shallower depths and confined geography, leading to faster wave steepening and higher risks to small craft.[6] |