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Dadonghai Swell Statistics, August: All Swell – Any Wind

This chart illustrates the variation of swells directed at Dadonghai over a normal August, based on 2976 NWW3 model predictions since 2006 (values every 3 hours). The wave model does not forecast surf and wind right at the shore so we have chosen the best grid node based on what we know about Dadonghai. In the case of Dadonghai, the best grid node is 25 km away (16 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 occurred only 57% of the time. Green and yellow illustrate increasing swell sizes and largest swells greater than >3m (>10ft) are shown in red. In both graphs, the area of any colour is proportional to how commonly that size swell occurs.

The diagram implies that the most common swell direction, shown by the largest spokes, was S (which was the same as the most common wind direction). Because the wave model grid is away from the coast, sometimes a strong offshore wind blows largest waves away from Dadonghai and out to sea. We group these 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 surfable at Dadonghai, you can view an alternative image that shows only the swells that were predicted to coincide with glassy or offshore wind conditions. During a typical August, swells large enough to cause good for surfing waves at Dadonghai run for about 4% 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.