The figure describes the variation of swells directed at Corona Del Mar Jetty through a typical March and is based upon 1724 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 Corona Del Mar Jetty, and at Corona Del Mar Jetty the best grid node is 16 km away (10 miles).
The rose diagram shows the distribution of swell sizes and directions, while the graph at the bottom shows the same thing but lacks direction information. Five colours show increasing wave sizes. The smallest swells, less than 0.5m (1.5 feet), high are coloured blue. These happened only 23% of the time. Green and yellow represent increasing swell sizes and red represents highest swells greater than >3m (>10ft). In both graphs, the area of any colour is proportional to how frequently that size swell was forecast.
The diagram suggests that the dominant swell direction, shown by the longest spokes, was SSW, whereas the the dominant wind blows from the W. Because the wave model grid is away from the coast, sometimes a strong offshore wind blows largest waves away from Corona Del Mar Jetty 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 surfable at Corona Del Mar Jetty, 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 March, swells large enough to cause good for surfing waves at Corona Del Mar Jetty run for about 9% 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.