Marine weather warnings are issued to ensure the safety of those on or near the water. These alerts provide timely information about potentially dangerous conditions that could affect maritime activities. Among these, a Special Marine Warning is a specific and urgent alert. This article explains what a Special Marine Warning entails and outlines the necessary actions to take when one is issued.
What a Special Marine Warning Signifies
A Special Marine Warning is an urgent, short-term alert issued by the National Weather Service (NWS) for hazardous conditions affecting coastal waters, the Great Lakes, and other navigable waterways. These warnings cover conditions of short duration, generally lasting up to two hours. They are triggered by sustained marine thunderstorm winds or associated gusts of 34 knots (39 miles per hour) or greater. Such winds can capsize small boats.
Warnings can also be issued for hail measuring three-quarters of an inch or more, or for waterspouts. These events are localized and short-lived. The warning may also be prompted by mesoscale events like a strong cold front or squall line, producing winds or gusts of 34 knots or greater. The NWS issues these warnings for all boaters.
Safety Measures to Take
When a Special Marine Warning is issued, immediate action is essential for those on or near the water. Mariners should stay informed by monitoring weather updates through marine radios, weather applications, or official NWS channels. If on the water, head to the nearest safe harbor or sheltered location. Have an escape plan to ensure your route back to land is not cut off by developing storms.
Boaters should reduce speed while maintaining enough power for steerage to manage waves and high winds. Close all hatches, windows, and doors to minimize water entry and secure loose gear. Turn on navigation lights, even during daylight, to increase visibility to other vessels and potential rescue teams. Passengers should wear life jackets, and if lightning is a threat, stay below decks and away from metal objects.
Differentiating from Other Marine Alerts
A Special Marine Warning is distinct from other common marine alerts in its specific nature and duration. A Small Craft Advisory is issued for sustained winds between 20 to 33 knots (24 to 38 miles per hour) or hazardous sea conditions. Unlike a Special Marine Warning, a Small Craft Advisory does not prohibit boating but advises caution.
A Gale Warning signifies sustained winds ranging from 34 to 47 knots (39 to 54 miles per hour). This alert covers broader areas and longer durations than a Special Marine Warning. A Storm Warning is issued for even stronger sustained winds of 48 knots (55 miles per hour) or more. These warnings indicate more widespread and prolonged severe conditions. The Special Marine Warning, in contrast, focuses on sudden, severe, localized, and short-duration threats like squalls, thunderstorms with strong gusts, or waterspouts.