This image shows only the swells directed at Walton Rocks (Power Plant) that coincided with light winds or offshore conditions over a normal November. It is based on 1680 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 show increasing swell sizes and biggest swells greater than >3m (>10ft) are shown in red. In both graphs, the area of any colour is proportional to how commonly that size swell was forecast.
The diagram implies that the most common swell direction, shown by the longest spokes, was ENE (which was the same as the prevailing wind direction). 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 15% of the time, equivalent to 4 days. Open sea swells exceeding >3m (>10ft) are unlikely to occur in a normal November. Taking into account the fraction of these swells that coincided with expected offshore winds, and given the fact that Walton Rocks (Power Plant) is exposed to open water swells, we estimate that clean surf can be found at Walton Rocks (Power Plant) about 15% of the time and that surf is messed up by onshore wind 81% of the time. This is means that we expect 29 days with waves in a typical November, of which 4 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.