This picture shows the variation of swells directed at Killer Point through a typical November. It is based on 1680 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 Killer Point. In the case of Killer Point, the best grid node is 26 km away (16 miles).
The rose diagram describes the distribution of swell sizes and directions, while the graph at the bottom shows the same thing but 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 only 1.2% of the time. Green and yellow represent increasing swell sizes and red represents the biggest swells, greater than >3m (>10ft). In both graphs, the area of any colour is proportional to how commonly that size swell was forecast.
The diagram implies that the most common swell direction, shown by the biggest spokes, was NW, whereas the the prevailing wind blows from the NNE. Because the wave model grid is out to sea, sometimes a strong offshore wind blows largest waves away from Killer Point and offshore. We lump these in with the no surf category of the bar chart. To simplify things we don't show these in the rose diagram. Because wind determines whether or not waves are surfable at Killer Point, you can load a different image that shows only the swells that were forecast to coincide with glassy or offshore wind conditions. Over an average November, swells large enough to cause good for surfing waves at Killer Point run for about 77% 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.