Annestown Swell Statistics, Autumn: Surf with Light or Offshore Winds
This image shows only the swells directed at Annestown 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 represent increasing swell sizes and red shows the biggest swells, greater than >3m (>10ft). In both graphs, the area of any colour is proportional to how commonly that size swell occurs.
The diagram implies that the most common swell direction, shown by the longest spokes, was SW, whereas the the prevailing wind blows from the WSW. 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 1.5% of the time, equivalent to 1 days. Open sea swells exceeding >3m (>10ft) are unlikely to happen in a normal northern hemisphere autumn. Taking into account the proportion of these swells that coincided with predicted offshore winds, and given the fact that Annestown is slightly protected from open water swells, we calculate that clean surf can be found at Annestown about 1.5% of the time and that surf is spoilt by onshore wind 26% of the time. This is means that we expect 25 days with waves in a typical northern hemisphere autumn, of which 1 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.