The rose diagram shows only the swells directed at Ansteys that coincided with light winds or offshore conditions over a normal August. It is based on 1736 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 show increasing swell sizes and red shows largest 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 E, whereas the the most common wind blows from the NNE. 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 19% of the time, equivalent to 6 days. Open sea swells exceeding >3m (>10ft) are unlikely to arise in a normal August but 5% of the time we expect swell in the range 2-3m (6.5-10ft) 5%, equivalent to (2 days). Taking into account the proportion of these swells that coincided with expected offshore winds, and given the fact that Ansteys is exposed to open water swells, we estimate that clean surf can be found at Ansteys about 19% of the time and that surf is blown out by onshore wind 32% of the time. This is means that we expect 16 days with waves in a typical August, of which 6 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.