This image shows only the swells directed at Walton Rocks (Power Plant) that coincided with light winds or offshore conditions through a typical January and is based upon 1728 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 biggest swells greater than >3m (>10ft) are shown in red. In both graphs, the area of any colour is proportional to how frequently that size swell was forecast.
The diagram suggests that the prevailing swell direction, shown by the longest spokes, was ENE, whereas the the prevailing wind blows from the ENE. 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 22% of the time, equivalent to 7 days. Open sea swells exceeding >3m (>10ft) are unlikely to occur in a normal January. Taking into account the proportion of these swells that coincided with predicted offshore winds, and given the fact that Walton Rocks (Power Plant) is exposed to open water swells, we calculate that clean surf can be found at Walton Rocks (Power Plant) about 22% of the time and that surf is messed up by onshore wind 60% of the time. This is means that we expect 25 days with waves in a typical January, of which 7 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.