Shag Rock Surf Stats

The rose diagram describes the variation of swells directed at Shag Rock through a typical May, based on 3422 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 Shag Rock, and at Shag Rock the best grid node is 16 km away (10 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 illustrate increasing wave sizes. Blue shows the smallest swells, less that 0.5m (1.5 feet) high. These occurred only 1.6% of the time. Green and yellow show increasing swell sizes and red represents highest swells greater than >3m (>10ft). In either graph, the area of any colour is proportional to how often that size swell was forecast. The diagram indicates that the dominant swell direction, shown by the largest spokes, was WSW (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 Shag Rock and away from the coast. We lump these in with the no surf category of the bar chart. To avoid confusion we don't show these in the rose diagram. Because wind determines whether or not waves are clean enough to surf at Shag Rock, you can select a similar diagram that shows only the swells that were forecast to coincide with glassy or offshore wind conditions. Over an average May, swells large enough to cause surfable waves at Shag Rock run for about 98% of the time.

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