Abereiddy Swell Statistics, September: Surf with Light or Offshore Winds
The rose diagram shows only the swells directed at Abereiddy that coincided with light winds or offshore conditions through a typical September. It is based on 2400 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 illustrate increasing swell sizes and red illustrates the highest swells, greater than >3m (>10ft). In each graph, 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 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 5% of the time, equivalent to 2 days. Open sea swells exceeding >3m (>10ft) are unlikely to arise in a normal September. Taking into account the ratio of these swells that coincided with forecast 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 5% of the time and that surf is blown out by onshore wind 24% of the time. This is means that we expect 9 days with waves in a typical September, of which 2 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.