weather.mailasail.com/Franks-Weather/How-Waves-And…

Frank's Weather has some useful background on waves

"There are requests from time to time for more detailed forecasts of sea conditions. I have been asked why the UK does not include swell height in its marine forecasts.

Here, I try to explain...weather.mailasail.com/Franks-Weather/How-Waves-And…

Frank's Weather has some useful background on waves

"There are requests from time to time for more detailed forecasts of sea conditions. I have been asked why the UK does not include swell height in its marine forecasts.

Here, I try to explain how waves and swell are formed and why sea state can be so variable in space and time.

Sea state depends on wind, current, coastal topography, the depth and nature of the sea bed. A sailor should be able to predict, qualitatively, how rough the sea is likely to be using a local wind forecast, tidal atlas and charted warnings of overfills and eddies. As in all of sailing, predictions will improve with experience gained and lessons learned. It is my belief that sea state near the coast cannot usefully be predicted on the space/time scales of an inshore waters or offshore forecast.

Swell originates beyond the areas of local forecasts and varies depending on its source, so it is hard for a sailor to predict. It can be a hazard at some harbour entrances and, in those cases, swell forecasts for the coasts affected are valuable. " Show more