This image shows only the swells directed at Horseshoe that coincided with light winds or offshore conditions over a normal northern hemisphere autumn. It is based on 5144 predictions, one every 3 hours. The direction of the spokes show where quality surf generating swell comes from. Five colours represent increasing wave sizes. Very small swells of less than 0.5m (1.5 feet) high are shown in blue. Green and yellow represent increasing swell sizes and red illustrates the largest swells, greater than >3m (>10ft). In each graph, the area of any colour is proportional to how frequently that size swell was forecast.
The diagram suggests that the dominant swell direction, shown by the longest spokes, was WSW, whereas the the most common wind blows from the WNW. 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 31% of the time, equivalent to 28 days. Open sea swells exceeding >3m (>10ft) are unlikely to occur in a normal northern hemisphere autumn but 4% of the time you can expect swell in the range 1.3-2m (4-6.5ft) 4%, equivalent to (4 days). Taking into account the proportion of these swells that coincided with predicted offshore winds, and given the fact that Horseshoe is exposed to open water swells, we think that that clean surf can be found at Horseshoe about 31% of the time and that surf is blown out by onshore wind 20% of the time. This is means that we expect 46 days with waves in a typical northern hemisphere autumn, of which 28 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.