China Beach Surf Stats

The rose diagram describes the range of swells directed at China Beach through a typical May, based on 3402 NWW3 model predictions since 2007 (values every 3 hours). The wave model does not forecast surf and wind right at the shore so we have chosen the most applicable grid node based on what we know about China Beach. In this particular case the best grid node is 23 km away (14 miles). The rose diagram shows the distribution of swell directions and swell sizes, 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 61% of the time. Green and yellow show increasing swell sizes and red illustrates the highest swells, greater than >3m (>10ft). In each 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 NE, whereas the the dominant wind blows from the SSE. Because the wave model grid is offshore, sometimes a strong offshore wind blows largest waves away from China Beach and away from the coast. 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 plot. Because wind determines whether or not waves are clean enough to surf at China Beach, you can select a similar diagram that shows only the swells that were expected to coincide with glassy or offshore wind conditions. Over an average May, swells large enough to cause surfable waves at China Beach run for about 39% of the time.

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