This image shows only the swells directed at Horseshoe that coincided with light winds or offshore conditions through a typical northern hemisphere winter. It is based on 5048 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 illustrate increasing swell sizes and red illustrates highest swells greater than >3m (>10ft). In each graph, the area of any colour is proportional to how often that size swell was forecast.
The diagram indicates that the dominant swell direction, shown by the biggest spokes, was WSW, 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 49% of the time, equivalent to 45 days. Open sea swells exceeding >3m (>10ft) are unlikely to occur in a normal northern hemisphere winter but 10% of the time you can expect swell in the range 1.3-2m (4-6.5ft) 10%, equivalent to (9 days). Taking into account the proportion of these swells that coincided with expected offshore winds, and given the fact that Horseshoe is exposed to open water swells, we estimate that clean surf can be found at Horseshoe about 49% of the time and that surf is messed up by onshore wind 33% of the time. This is means that we expect 75 days with waves in a typical northern hemisphere winter, of which 45 days should be clean enough to surf.
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.