Gwithian Surf Stats

The rose diagram describes the variation of swells directed at Gwithian through an average May and is based upon 3440 NWW3 model predictions since 2007 (values every 3 hours). The wave model does not forecast surf and wind right at the coastline so we have chosen the most applicable grid node based on what we know about Gwithian. In this particular case the best grid node is 32 km away (20 miles). The rose diagram shows the distribution of swell directions and swell sizes, while the graph at the bottom shows the same thing but lacks direction information. Five colours illustrate increasing wave sizes. Blue shows the smallest swells, less that 0.5m (1.5 feet) high. These happened only 14% of the time. Green and yellow illustrate increasing swell sizes and red represents 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 largest spokes, was W, whereas the the dominant wind blows from the WNW. Because the wave model grid is away from the coast, sometimes a strong offshore wind blows largest waves away from Gwithian and out to sea. We combine these with the no surf category of the bar chart. To keep it simple we don't show these in the rose graph. Because wind determines whether or not waves are surfable at Gwithian, you can select a similar diagram that shows only the swells that were expected to coincide with glassy or offshore wind conditions. In a typical May, swells large enough to cause good for surfing waves at Gwithian run for about 46% of the time.

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