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ASA 103 Navigation & Weather

· ASA103,sailing

Define "small craft advisory" and "gale warning" and describe precautions to be taken for each.

Although "small craft" is not officially defined, the recommendation is for sailors at the ASA 103 level to heed small craft advisories. These are issued by the National Weather Service and broadcasted by NOAA Weather Radio during hazardous wind and sea conditions.

A gale warning is an alert for winds exceeding 34 knots, but under 47 knots. These winds should be considered very dangerous..

Describe how to prevent undue magnetic influence on a compass.

A compass is simply a magnet that rotates on a low friction point so that it will point towards the Magnetic North Pole. Objects that contain iron, such as the engine, can affect which direction the compass points in.

Describe the dangers of, and how to avoid, a 'lee shore'

The best way to avoid crashing your boat into the shore that is leeward is by giving yourself plenty of space. Stay aware of any obstruction that the wind could blow you into.

Obtain and interpret marine weather information

You can find marine weather forecasts by region on the National Weather Service website. There are also third party applications and other commercial weather services that can provide forecasts — these use data both from the NWS as well as other sources to compile their own forecasts. It is recommended to check the weather forecast before sailing, but once on the boat you can obtain updated forecasts by turning on your VHF radio and tuning it to NOAA's weather radio station, which runs in a loop continuously. 

Describe and identify Cumulonimbus clouds and what dangers they may signify

If you see cumulonimbus clouds, it means there is a good chance of thunderstorms with lightning, rain, and wind. These clouds tend to be large and extend high into the air, often forming a cauliflower or anvil shape.

 The best thing to do is avoid it by sailing 90 degrees to it, or to find shelter by returning to port or finding a protected place to anchor. If you are going to get caught in it, take down and furl all sails so they do not get damaged and turn on your auxiliary engine to maintain control of the boat. Close all ports and hatches to keep water out. Because of lightning and falling overboard risks, try to limit the number of people on deck and send crew members below. Ideally everyone should be wearing their life vests.