Porth Nefyn Surf Stats

The graph describes the variation of swells directed at Porth Nefyn through a typical May, based on 3438 NWW3 model predictions since 2007 (values every 3 hours). The wave model does not forecast surf and wind right at the shore so we have chosen the optimum 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 sizes and directions, while the graph at the bottom shows the same thing but without direction information. Five colours show increasing wave sizes. The smallest swells, less than 0.5m (1.5 feet), high are coloured blue. These happened 65% of the time. Green and yellow illustrate increasing swell sizes and red illustrates the highest swells, greater than >3m (>10ft). In each graph, the area of any colour is proportional to how commonly that size swell happens. The diagram implies that the prevailing swell direction, shown by the longest spokes, was SW (which was the same as the dominant wind direction). 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 group these with the no surf category of the bar chart. To avoid confusion we don't show these in the rose plot. Because wind determines whether or not waves are good for surfing at Porth Nefyn, you can load a different image that shows only the swells that were expected to coincide with glassy or offshore wind conditions. Over an average May, swells large enough to cause clean enough to surf waves at Porth Nefyn run for about 1.0% of the time.

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