This image shows only the swells directed at Alexandra Headland that coincided with light winds or offshore conditions over a normal 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 show increasing wave sizes. The smallest swells, less than 0.5m (1.5 feet), high are coloured blue. Green and yellow show increasing swell sizes and red represents biggest swells greater than >3m (>10ft). In both graphs, the area of any colour is proportional to how commonly that size swell happens.
The diagram implies that the dominant swell direction, shown by the largest spokes, was SE, whereas the the prevailing 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 44% of the time, equivalent to 13 days. Open sea swells exceeding >3m (>10ft) are unlikely to arise in a normal June but 10% of the time we expect swell in the range 2-3m (6.5-10ft) 10%, equivalent to (3 days). Taking into account the fraction of these swells that coincided with forecast offshore winds, and given the fact that Alexandra Headland is exposed to open water swells, we estimate that clean surf can be found at Alexandra Headland about 44% of the time and that surf is messed up by onshore wind 43% of the time. This is means that we expect 26 days with waves in a typical June, of which 13 days should be clean enough to surf.
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.