Trearddur Bay (Holy Island) Surf Stats

The rose diagram describes the variation of swells directed at Trearddur Bay (Holy Island) through an average October and is based upon 2975 NWW3 model predictions since 2008 (values every 3 hours). The wave model does not forecast wind and surf right at the shore so we have chosen the best grid node based on what we know about Trearddur Bay (Holy Island), and at Trearddur Bay (Holy Island) the best grid node is 26 km away (16 miles). The rose diagram illustrates the distribution of swell sizes and swell direction, while the graph at the bottom shows the same thing but lacks direction information. Five colours show increasing wave sizes. The smallest swells, less than 0.5m (1.5 feet), high are coloured blue. These happened only 44% of the time. Green and yellow represent increasing swell sizes and highest swells greater than >3m (>10ft) are shown in red. In each graph, the area of any colour is proportional to how commonly that size swell was forecast. The diagram implies that the prevailing swell direction, shown by the biggest spokes, was SW (which was the same as the dominant wind direction). Because the wave model grid is offshore, sometimes a strong offshore wind blows largest waves away from Trearddur Bay (Holy Island) and away from the coast. We combine these with the no surf category of the bar chart. To keep it simple we don't show these in the rose diagram. Because wind determines whether or not waves are clean enough to surf at Trearddur Bay (Holy 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 surfable waves at Trearddur Bay (Holy Island) run for about 26% of the time.

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