This image shows only the swells directed at Kerloch that coincided with light winds or offshore conditions over a normal northern hemisphere spring and is based upon 4850 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 represent increasing swell sizes and red represents the highest swells, greater than >3m (>10ft). In either graph, the area of any colour is proportional to how commonly that size swell occurs.
The diagram implies that the dominant swell direction, shown by the longest spokes, was W, whereas the the dominant wind blows from the NNW. 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 25% of the time, equivalent to 23 days. Open water swells exceeding >3m (>10ft) only happen 0.6% of the time in a typical northern hemisphere spring, equivalent to just one day but 5% of the time we expect swell in the range 2-3m (6.5-10ft) 5%, equivalent to (5 days). Taking into account the fraction of these swells that coincided with forecast offshore winds, and given the fact that Kerloch is exposed to open water swells, we think that that clean surf can be found at Kerloch about 25% of the time and that surf is spoilt by onshore wind 33% of the time. This is means that we expect 53 days with waves in a typical northern hemisphere spring, of which 23 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.