Three Arch Bay Surf Stats

The graph shows the variation of swells directed at Three Arch Bay over a normal November, based on 3347 NWW3 model predictions since 2006 (values every 3 hours). The wave model does not forecast wind or surf right at the coastline so we have chosen the best grid node based on what we know about Three Arch Bay, and at Three Arch Bay the best grid node is 21 km away (13 miles). The rose diagram shows the distribution of swell sizes and swell direction, 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 occurred 15% of the time. Green and yellow show increasing swell sizes and red represents biggest swells greater than >3m (>10ft). In either graph, the area of any colour is proportional to how frequently that size swell occurs. The diagram suggests that the prevailing swell direction, shown by the largest spokes, was SW, whereas the the prevailing wind blows from the WNW. Because the wave model grid is out to sea, sometimes a strong offshore wind blows largest waves away from Three Arch Bay and offshore. We group 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 clean enough to surf at Three Arch Bay, you can select a similar diagram that shows only the swells that were forecast to coincide with glassy or offshore wind conditions. During a typical November, swells large enough to cause surfable waves at Three Arch Bay run for about 85% of the time.

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