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Sailing reference
Clear explanations of the language used in navigation, pilotage, weather, safety and life under sail.
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A travelling area of low pressure carrying fronts and bad weather
Forms on the polar front where cold and warm air masses meet, then deepens as it tracks generally eastward, typically at 20 to 30 knots in the temperate zone. Its classic structure has a warm front ahead, a warm sector, and a faster cold front behind that eventually catches up to form an occlusion. Winds circulate anticlockwise in the Northern Hemisphere and back then veer sharply as the fronts pass.
Read definition →Two unequal high waters and two unequal low waters daily
Results from comparable semi-diurnal and diurnal constituent amplitudes, giving a marked diurnal inequality with higher high water, lower high water, higher low water and lower low water each cycle. Typical of the Pacific coasts of North America and much of Australia. Form factors between roughly 0.25 and 3.0 denote mixed regimes. Navigators there must identify which of the day's two low waters is the critical one for clearance calculations.
Read definition →A one-touch button storing the position where someone fell in
Pressing the man overboard key on a GNSS receiver, plotter or DSC radio instantly saves the current position as a waypoint and switches the display to bearing, range and often a return course to it. Because the casualty drifts with tidal stream and wind while the boat manoeuvres, the mark is a datum for the start of the search, not the person's present position, and a dedicated lookout must still be posted.
Sailing reference
Clear explanations of the language used in navigation, pilotage, weather, safety and life under sail.