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Diamond Head Swell Statistics, Summer: All Swell – Any Wind

This chart shows the combination of swells directed at Diamond Head through an average southern hemisphere summer and is based upon 7765 NWW3 model predictions since 2006 (values every 3 hours). The wave model does not forecast wind and surf right at the shore so we have chosen the optimum grid node based on what we know about Diamond Head. In this particular case the best grid node is 31 km away (19 miles).

The rose diagram illustrates 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 happened only 25% of the time. Green and yellow represent increasing swell sizes and red shows the biggest swells, greater than >3m (>10ft). In either graph, the area of any colour is proportional to how commonly that size swell occurs.

The diagram implies that the prevailing swell direction, shown by the biggest spokes, was E, whereas the the prevailing wind blows from the ENE. Because the wave model grid is out to sea, sometimes a strong offshore wind blows largest waves away from Diamond Head and offshore. We group these with the no surf category of the bar chart. To avoid confusion we don't show these in the rose graph. Because wind determines whether or not waves are clean enough to surf at Diamond Head, 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 southern hemisphere summer, swells large enough to cause surfable waves at Diamond Head run for about 75% 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.