Avon Pier Swell Statistics, Autumn: Surf with Light or Offshore Winds
This image shows only the swells directed at Avon Pier that coincided with light winds or offshore conditions through a typical 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 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 represents highest swells greater than >3m (>10ft). In both graphs, 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 SSE, whereas the the dominant wind blows from the NNW. 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 24% of the time, equivalent to 22 days. Open sea swells exceeding >3m (>10ft) are unlikely to arise 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 ratio of these swells that coincided with expected offshore winds, and given the fact that Avon Pier is exposed to open water swells, we estimate that clean surf can be found at Avon Pier about 24% of the time and that surf is blown out by onshore wind 29% of the time. This is means that we expect 48 days with waves in a typical northern hemisphere autumn, of which 22 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.