Bay of Skaill Surf Stats

The figure describes the variation of swells directed at Bay of Skaill through a typical April. It is based on 3360 NWW3 model predictions since 2007 (values every 3 hours). The wave model does not forecast wind or surf right at the coast so we have chosen the optimum grid node based on what we know about Bay of Skaill, and at Bay of Skaill the best grid node is 11 km away (7 miles). The rose diagram describes the distribution of swell directions and swell sizes, 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 22% of the time. Green and yellow represent 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 occurs. The diagram implies that the most common swell direction, shown by the largest spokes, was WNW, whereas the the dominant wind blows from the SSW. Because the wave model grid is out to sea, sometimes a strong offshore wind blows largest waves away from Bay of Skaill and offshore. 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 Bay of Skaill, you can select a similar diagram that shows only the swells that were expected to coincide with glassy or offshore wind conditions. Over an average April, swells large enough to cause good for surfing waves at Bay of Skaill run for about 78% of the time.

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