Llanddwyn Island Surf Stats

The figure illustrates the combination of swells directed at Llanddwyn Island through an average October. It is based on 3471 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 Llanddwyn Island. In this particular case the best grid node is 16 km away (10 miles). The rose diagram illustrates the distribution of swell sizes and swell direction, while the graph at the bottom shows the same thing but without direction information. Five colours represent increasing wave sizes. Very small swells of less than 0.5m (1.5 feet) high are shown in blue. These happened 42% of the time. Green and yellow show increasing swell sizes and red shows largest 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 most common wind blows from the SSW. Because the wave model grid is offshore, sometimes a strong offshore wind blows largest waves away from Llanddwyn Island and away from the coast. We combine these 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 surfable at Llanddwyn Island, you can select a similar diagram that shows only the swells that were predicted to coincide with glassy or offshore wind conditions. In a typical October, swells large enough to cause good for surfing waves at Llanddwyn Island run for about 58% of the time.

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