The rose diagram shows only the swells directed at Belgas 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 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 illustrates the highest swells, greater than >3m (>10ft). In both graphs, the area of any colour is proportional to how often that size swell happens.
The diagram indicates that the dominant swell direction, shown by the biggest spokes, was NW (which was the same as the dominant wind direction). 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 14% of the time, equivalent to 13 days. Open water swells exceeding >3m (>10ft) only arise 1.1% of the time in a typical northern hemisphere autumn, equivalent to just one day 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 we think that that clean surf can be found at Belgas about 14% of the time and that surf is blown out by onshore wind 47% of the time. This is means that we expect 56 days with waves in a typical northern hemisphere autumn, of which 13 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.