San Miguel - Areias Swell Statistics, Autumn: Surf with Light or Offshore Winds
This image shows only the swells directed at San Miguel - Areias that coincided with light winds or offshore conditions through a typical northern hemisphere autumn and is based upon 7252 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 largest swells greater than >3m (>10ft) are shown in red. In each graph, the area of any colour is proportional to how commonly that size swell occurs.
The diagram implies that the dominant swell direction, shown by the biggest spokes, was NW, whereas the the most common wind blows from the W. 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 21% of the time, equivalent to 19 days. Open water swells exceeding >3m (>10ft) only happen 1.4% of the time in a typical northern hemisphere autumn, equivalent to just one day but 10% of the time we expect swell in the range 2-3m (6.5-10ft) 10%, equivalent to (9 days). Taking into account the proportion of these swells that coincided with forecast offshore winds, and given the fact that San Miguel - Areias is slightly protected from open water swells, we think that that clean surf can be found at San Miguel - Areias about 21% of the time and that surf is messed up by onshore wind 46% of the time. This is means that we expect 61 days with waves in a typical northern hemisphere autumn, of which 19 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.