The graph shows the combination of swells directed at Fort Point through an average June. It is based on 1600 NWW3 model predictions since 2006 (values every 3 hours). The wave model does not forecast wind or surf right at the shore so we have chosen the optimum grid node based on what we know about Fort Point. In the case of Fort Point, the best grid node is 34 km away (21 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 illustrate increasing wave sizes. Blue shows the smallest swells, less that 0.5m (1.5 feet) high. These were forecast only 32% of the time. Green and yellow show increasing swell sizes and red shows biggest swells greater than >3m (>10ft). In both graphs, the area of any colour is proportional to how often that size swell occurs.
The diagram indicates that the most common swell direction, shown by the longest spokes, was WNW (which was the same as the prevailing wind direction). Because the wave model grid is away from the coast, sometimes a strong offshore wind blows largest waves away from Fort Point and out to sea. 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 diagram. Because wind determines whether or not waves are good for surfing at Fort Point, you can load a different image that shows only the swells that were expected to coincide with glassy or offshore wind conditions. In a typical June, swells large enough to cause clean enough to surf waves at Fort Point run for about 37% 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.