Aberarth Swell Statistics, December: Surf with Light or Offshore Winds
This image shows only the swells directed at Aberarth that coincided with light winds or offshore conditions over a normal December and is based upon 2457 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 show increasing swell sizes and biggest 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 was forecast.
The diagram implies that the most common swell direction, shown by the longest spokes, was SW, whereas the the prevailing 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 occur 2% of the time in a typical December, equivalent to just one day but 8% of the time we expect swell in the range 2-3m (6.5-10ft) 8%, equivalent to (2 days). Taking into account the fraction of these swells that coincided with expected 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 18% of the time and that surf is spoilt by onshore wind 31% of the time. This is means that we expect 15 days with waves in a typical December, 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.