Weather by Lee

Inside Weather: Small Craft Advisory

A Small Craft Advisory is an important function of the National Weather Service marine forecast program. It is basically putting your tax dollars to work.

There are a few choices you have to receive this information. You can use the channel 16 voice broadcast in U.S. waters, which the Coast Guard will issue when a SCA is issued, or in many areas there are specifi ed stations on the VHF which broadcast weather continuously. Then there is the alpha numeric (NAVTEX) text message or the National Digital Forecast Database graphics format. These are all a form of safety advisory to mariners...as issued by coastal and the Great Lakes National Weather Service Forecast Offi ces. Most sailors will use the Coastal Waters Forecast or Near Shore Marine Forecast to monitor their weather.

What governs the issuance of a Small Craft Advisory is specifi c to geographic areas (e.g. for winds it will be somewhere between 20 to 33 knots). The criteria for waves will have more variability. For example, in Morehead City, NC, Signifi cant Wave Height... defi ned as the average of one third of the waves present... is fi ve feet, while in Eureka, CA, it is 15 feet. A Small Craft Advisory may also be issued when sea or lake ice exists that could be hazardous to small boats.

There is no precise defi nition of a small craft as to a boat’s size. Any vessel that may be adversely affected by Small Craft Advisory criteria should be considered a small craft. Other important considerations must include the experience of the vessel operator (including crew), and the type and sea worthiness of the vessel impacted. Each geographic area of the U.S. has its own separate criteria, often based on casualties or vessel damage (in other words, having been written in blood). If you’d like to keep up with these and other weather phenomena you can refer to my web page (www.weatherbylee. com) and under “links” on the drop down menu at the top click “marine links” and then scroll down further until you get to the National Weather Service (NWS) Marine program highlighted in red. You can then refer to the U.S. Map on the upper left hand corner of the NWS Marine Forecast page. You can click on the map to expand the map size. Note that each “red dot” represents a local National Weather Service Forecast Offi ce that has marine weather advisory, warnings, and forecast responsibilities. Choose the local National Weather Service Forecast Offi ce of interest and click on it to get your marine forecast in either text or graphic format as seen here.

And that is how to fi nd Small Craft Advisories!

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