Statistiques de Surf de Caerhays

The figure shows the variation of swells directed at Caerhays through a typical August. It is based on 3574 NWW3 model predictions since 2006 (values every 3 hours). The wave model does not forecast surf and wind right at the shore so we have chosen the best grid node based on what we know about Caerhays, and at Caerhays the best grid node is 28 km away (17 miles). The rose diagram describes the distribution of swell sizes and directions, while the graph at the bottom shows the same thing without direction information. Five colours show increasing wave sizes. The smallest swells, less than 0.5m (1.5 feet), high are coloured blue. These were forecast only 73% of the time. Green and yellow represent increasing swell sizes and red represents biggest swells greater than >3m (>10ft). In either graph, the area of any colour is proportional to how commonly that size swell was forecast. The diagram implies that the dominant swell direction, shown by the longest spokes, was SW, whereas the the prevailing wind blows from the W. Because the wave model grid is away from the coast, sometimes a strong offshore wind blows largest waves away from Caerhays and out to sea. We combine these with the no surf category of the bar chart. To simplify things we don't show these in the rose diagram. Because wind determines whether or not waves are clean enough to surf at Caerhays, you can select a similar diagram that shows only the swells that were forecast to coincide with glassy or offshore wind conditions. Over an average August, swells large enough to cause surfable waves at Caerhays run for about 15% of the time.

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