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Grannys Grave Beach Swell Statistics, August: All Swell – Any Wind

The rose diagram illustrates the combination of swells directed at Grannys Grave Beach through an average August, based on 2976 NWW3 model predictions since 2006 (values every 3 hours). The wave model does not forecast wind and surf right at the coastline so we have chosen the optimum grid node based on what we know about Grannys Grave Beach. In this particular case 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 without direction information. Five colours illustrate increasing wave sizes. Blue shows the smallest swells, less that 0.5m (1.5 feet) high. These happened only 99% of the time. Green and yellow illustrate increasing swell sizes and red illustrates the largest swells, greater than >3m (>10ft). In each graph, the area of any colour is proportional to how often that size swell happens.

The diagram indicates that the dominant swell direction, shown by the biggest spokes, was S, whereas the the most common wind blows from the WNW. Because the wave model grid is out to sea, sometimes a strong offshore wind blows largest waves away from Grannys Grave Beach and offshore. We lump these in 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 Grannys Grave Beach, you can load a different image that shows only the swells that were predicted to coincide with glassy or offshore wind conditions. In a typical August, swells large enough to cause surfable waves at Grannys Grave Beach run for about 1.0% of the time.

IMPORTANT: Beta version feature! Swell heights are open water values from NWW3. There is no attempt to model near-shore effects. Coastal wave heights will generally be less, especially if the break does not have unobstructed exposure to the open ocean.