This image describes the variation of swells directed at Boucan Lefts over a normal southern hemisphere autumn. It is based on 4842 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 best grid node based on what we know about Boucan Lefts. In the case of Boucan Lefts, the best grid node is 24 km away (15 miles).
The rose diagram shows the distribution of swell directions and swell sizes, while the graph at the bottom shows the same thing but lacks direction information. Five colours illustrate increasing wave sizes. Blue shows the smallest swells, less that 0.5m (1.5 feet) high. These occurred only 11% of the time. Green and yellow illustrate increasing swell sizes and red represents highest swells greater than >3m (>10ft). In each graph, the area of any colour is proportional to how commonly that size swell occurs.
The diagram implies that the dominant swell direction, shown by the biggest spokes, was SSW, whereas the the dominant wind blows from the E. Because the wave model grid is out to sea, sometimes a strong offshore wind blows largest waves away from Boucan Lefts and offshore. We combine these with the no surf category of the bar chart. To simplify things we don't show these in the rose graph. Because wind determines whether or not waves are surfable at Boucan Lefts, 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 southern hemisphere autumn, swells large enough to cause good for surfing waves at Boucan Lefts run for about 89% 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.