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

This picture shows the variation of swells directed at Grannys Grave Beach through a typical December, based on 2953 NWW3 model predictions since 2006 (values every 3 hours). The wave model does not forecast surf and wind right at the coast so we have chosen the best 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 sizes and directions, while the graph at the bottom shows the same thing 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 only 98% of the time. Green and yellow represent increasing swell sizes and red illustrates the biggest swells, greater than >3m (>10ft). In either graph, the area of any colour is proportional to how often that size swell occurs.

The diagram indicates that the dominant swell direction, shown by the biggest spokes, was SE, whereas the the prevailing wind blows from the SSW. Because the wave model grid is away from the coast, sometimes a strong offshore wind blows largest waves away from Grannys Grave Beach and out to sea. We combine these with the no surf category of the bar chart. To simplify things we don't show these in the rose plot. Because wind determines whether or not waves are good for surfing at Grannys Grave Beach, you can view an alternative image that shows only the swells that were expected to coincide with glassy or offshore wind conditions. Over an average December, swells large enough to cause clean enough to surf waves at Grannys Grave Beach run for about 2.0% 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.