Abereiddy Swell Statistics, Autumn: Surf with Light or Offshore Winds
This image shows only the swells directed at Abereiddy that coincided with light winds or offshore conditions over a normal northern hemisphere autumn. It is based on 7252 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 show increasing swell sizes and highest swells greater than >3m (>10ft) are shown in red. In each graph, the area of any colour is proportional to how often that size swell occurs.
The diagram indicates that the prevailing 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 10% of the time, equivalent to 9 days. Open sea swells exceeding >3m (>10ft) are unlikely to happen in a normal northern hemisphere autumn but 4% of the time we expect swell in the range 2-3m (6.5-10ft) 4%, equivalent to (4 days). Taking into account the proportion of these swells that coincided with predicted offshore winds, and given the fact that Abereiddy is slightly protected from open water swells, we calculate that clean surf can be found at Abereiddy about 10% of the time and that surf is spoilt by onshore wind 37% of the time. This is means that we expect 43 days with waves in a typical northern hemisphere autumn, of which 9 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.