San Pancho (San Francisco) Surf Stats

The rose diagram describes the variation of swells directed at San Pancho (San Francisco) over a normal May. It is based on 3422 NWW3 model predictions since 2007 (values every 3 hours). The wave model does not forecast surf and wind right at the coast so we have chosen the optimum grid node based on what we know about San Pancho (San Francisco). In this particular case the best grid node is 14 km away (9 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 illustrate increasing wave sizes. Blue shows the smallest swells, less that 0.5m (1.5 feet) high. These were forecast only 0.4% of the time. Green and yellow illustrate increasing swell sizes and highest swells greater than >3m (>10ft) are shown in red. In either graph, the area of any colour is proportional to how frequently that size swell occurs. The diagram suggests that the prevailing swell direction, shown by the largest spokes, was SSW, whereas the the dominant wind blows from the NNW. Because the wave model grid is away from the coast, sometimes a strong offshore wind blows largest waves away from San Pancho (San Francisco) and out to sea. We lump these in 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 clean enough to surf at San Pancho (San Francisco), you can view an alternative image that shows only the swells that were forecast to coincide with glassy or offshore wind conditions. During a typical May, swells large enough to cause surfable waves at San Pancho (San Francisco) run for about 100% of the time.

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