This picture illustrates the combination of swells directed at Pilgrim Avenue through an average April. It is based on 1638 NWW3 model predictions since 2007 (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 Pilgrim Avenue, and at Pilgrim Avenue the best grid node is 41 km away (25 miles).
The rose diagram illustrates 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 happened only 25% of the time. Green and yellow show increasing swell sizes and largest swells greater than >3m (>10ft) are shown in red. In either graph, the area of any colour is proportional to how often that size swell occurs.
The diagram indicates that the dominant swell direction, shown by the longest spokes, was SSE, whereas the the most common wind blows from the WSW. Because the wave model grid is offshore, sometimes a strong offshore wind blows largest waves away from Pilgrim Avenue and away from the coast. 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 clean enough to surf at Pilgrim Avenue, 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 April, swells large enough to cause surfable waves at Pilgrim Avenue run for about 42% 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.