This image shows only the swells directed at Gansbaai that coincided with light winds or offshore conditions through a typical June. It is based on 1594 predictions, one every 3 hours. The direction of the spokes show where quality surf generating swell comes from. Five colours represent increasing wave sizes. Very small swells of less than 0.5m (1.5 feet) high are shown in blue. Green and yellow show 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 was forecast.
The diagram implies that the prevailing swell direction, shown by the largest spokes, was SW, whereas the the most common wind blows from the WNW. 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 36% of the time, equivalent to 11 days. Expect open water swells to exceed >3m (>10ft) 8% of the time (2 days). Taking into account the ratio of these swells that coincided with forecast offshore winds, and given the fact that Gansbaai is slightly protected from open water swells, we calculate that clean surf can be found at Gansbaai about 36% of the time and that surf is blown out by onshore wind 59% of the time. This is means that we expect 28 days with waves in a typical June, of which 11 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.