This image shows only the swells directed at Lackan Bay 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 represent increasing wave sizes. Very small swells of less than 0.5m (1.5 feet) high are shown in blue. Green and yellow represent increasing swell sizes and largest 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 happens.
The diagram implies that the prevailing swell direction, shown by the biggest spokes, was NW, whereas the the most common wind blows from the SW. 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 18% of the time, equivalent to 5 days. Open water swells exceeding >3m (>10ft) only arise 2% of the time in a typical April, equivalent to just one day 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 expected offshore winds, and given the fact that Lackan Bay is slightly protected from open water swells, we calculate that clean surf can be found at Lackan Bay about 18% of the time and that surf is blown out by onshore wind 30% of the time. This is means that we expect 14 days with waves in a typical April, of which 5 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.