This image shows only the swells directed at Kanaha that coincided with light winds or offshore conditions through a typical April. 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 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 either graph, the area of any colour is proportional to how often that size swell was forecast.
The diagram indicates that the dominant swell direction, shown by the longest spokes, was NNE, whereas the the prevailing wind blows from the E. 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 46% of the time, equivalent to 14 days. Open sea swells exceeding >3m (>10ft) are unlikely to occur in a normal April but 18% of the time we expect swell in the range 2-3m (6.5-10ft) 18%, equivalent to (5 days). Taking into account the ratio of these swells that coincided with expected offshore winds we calculate that clean surf can be found at Kanaha about 46% of the time and that surf is messed up by onshore wind 15% of the time. This is means that we expect 18 days with waves in a typical April, of which 14 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.