Abereiddy Swell Statistics, Spring: Surf with Light or Offshore Winds
This image shows only the swells directed at Abereiddy that coincided with light winds or offshore conditions through a typical northern hemisphere spring. It is based on 6580 predictions, one every 3 hours. The direction of the spokes show where quality surf generating swell comes from. Five colours illustrate increasing wave sizes. Blue shows the smallest swells, less that 0.5m (1.5 feet) high. Green and yellow represent increasing swell sizes and red shows biggest swells greater than >3m (>10ft). In both graphs, the area of any colour is proportional to how commonly that size swell was forecast.
The diagram implies that the dominant swell direction, shown by the longest spokes, was SW, whereas the the prevailing wind blows from the W. 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 8% of the time, equivalent to 7 days. Open sea swells exceeding >3m (>10ft) are unlikely to occur in a normal northern hemisphere spring but 3% of the time we expect swell in the range 2-3m (6.5-10ft) 3%, equivalent to (3 days). Taking into account the ratio of these swells that coincided with predicted offshore winds, and given the fact that Abereiddy is slightly protected from open water swells, we estimate that clean surf can be found at Abereiddy about 8% of the time and that surf is blown out by onshore wind 23% of the time. This is means that we expect 28 days with waves in a typical northern hemisphere spring, of which 7 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.