Aberarth Swell Statistics, Winter: Surf with Light or Offshore Winds
This image shows only the swells directed at Aberarth that coincided with light winds or offshore conditions through a typical northern hemisphere winter. It is based on 6930 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 red illustrates 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 largest spokes, was SW (which was the same as the dominant 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 16% of the time, equivalent to 15 days. Open water swells exceeding >3m (>10ft) only happen 1.3% of the time in a typical northern hemisphere winter, equivalent to just one day but 7% of the time we expect swell in the range 2-3m (6.5-10ft) 7%, equivalent to (6 days). Taking into account the fraction of these swells that coincided with forecast offshore winds, and given the fact that Aberarth is slightly protected from open water swells, we think that that clean surf can be found at Aberarth about 16% of the time and that surf is blown out by onshore wind 27% of the time. This is means that we expect 39 days with waves in a typical northern hemisphere winter, of which 15 days should be clean enough to surf.
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.