Statistiques de Surf de Porth Nefyn

The figure describes the variation of swells directed at Porth Nefyn over a normal August. It is based on 3589 NWW3 model predictions since 2006 (values every 3 hours). The wave model does not forecast wind and surf right at the coast so we have chosen the most applicable grid node based on what we know about Porth Nefyn, and at Porth Nefyn the best grid node is 7 km away (4 miles). The rose diagram illustrates the distribution of swell directions and swell sizes, 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 occurred 49% of the time. Green and yellow illustrate increasing swell sizes and red represents the highest swells, greater than >3m (>10ft). In both graphs, the area of any colour is proportional to how commonly that size swell happens. The diagram implies that the dominant swell direction, shown by the largest spokes, was SW, whereas the the dominant wind blows from the WSW. Because the wave model grid is away from the coast, sometimes a strong offshore wind blows largest waves away from Porth Nefyn and out to sea. We lump these in with the no surf category of the bar chart. To simplify things we don't show these in the rose graph. Because wind determines whether or not waves are good for surfing at Porth Nefyn, you can view an alternative image that shows only the swells that were expected to coincide with glassy or offshore wind conditions. During a typical August, swells large enough to cause clean enough to surf waves at Porth Nefyn run for about 2.0% of the time.

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