Ocean Beach Swell Statistics, Spring: All Swell – Any Wind
The figure shows the combination of swells directed at Ocean Beach through a typical southern hemisphere spring, based on 6516 NWW3 model predictions since 2006 (values every 3 hours). The wave model does not forecast surf and wind right at the coast so we have chosen the best grid node based on what we know about Ocean Beach. In the case of Ocean Beach, the best grid node is 25 km away (16 miles).
The rose diagram illustrates the distribution of swell sizes and swell direction, while the graph at the bottom shows the same thing but 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 32% of the time. Green and yellow represent increasing swell sizes and red shows biggest swells greater than >3m (>10ft). In either graph, the area of any colour is proportional to how frequently that size swell happens.
The diagram suggests that the prevailing swell direction, shown by the largest spokes, was SE, whereas the the prevailing wind blows from the WNW. Because the wave model grid is away from the coast, sometimes a strong offshore wind blows largest waves away from Ocean Beach and out to sea. We combine these 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 surfable at Ocean Beach, you can view an alternative image that shows only the swells that were predicted to coincide with glassy or offshore wind conditions. Over an average southern hemisphere spring, swells large enough to cause good for surfing waves at Ocean Beach run for about 34% 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.