This image shows only the swells directed at Cap Ferret that coincided with light winds or offshore conditions through a typical January. It is based on 1728 predictions, one every 3 hours. The direction of the spokes show where quality surf generating swell comes from. Five colours illustrate increasing wave sizes. Blue shows the smallest swells, less that 0.5m (1.5 feet) high. Green and yellow represent increasing swell sizes and largest swells greater than >3m (>10ft) are shown in red. In each graph, the area of any colour is proportional to how commonly that size swell happens.
The diagram implies that the most common swell direction, shown by the longest spokes, was WNW, whereas the the most common wind blows from the S. The chart at the bottom shows the same thing but without direction information. For example, swells larger than 1.5 feet (0.5m) coincided with good wind conditions 40% of the time, equivalent to 12 days. Open sea swells exceeding >3m (>10ft) are unlikely to arise in a normal January but 13% of the time we expect swell in the range 2-3m (6.5-10ft) 13%, equivalent to (4 days). Taking into account the ratio of these swells that coincided with predicted offshore winds, and given the fact that Cap Ferret is exposed to open water swells, we estimate that clean surf can be found at Cap Ferret about 40% of the time and that surf is blown out by onshore wind 57% of the time. This is means that we expect 30 days with waves in a typical January, of which 12 days should be surfable.
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.