San Miguel - Areias Swell Statistics, September: 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 over a normal September. It is based on 2400 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 represents biggest swells greater than >3m (>10ft). In both graphs, the area of any colour is proportional to how frequently that size swell occurs.
The diagram suggests that the most common swell direction, shown by the longest spokes, was NNW, whereas the the prevailing 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 14% of the time, equivalent to 4 days. Open sea swells exceeding >3m (>10ft) are unlikely to happen in a normal September but 10% of the time you can expect swell in the range 1.3-2m (4-6.5ft) 10%, equivalent to (3 days). Taking into account the fraction of these swells that coincided with expected offshore winds, and given the fact that San Miguel - Areias is slightly protected from open water swells, we calculate that clean surf can be found at San Miguel - Areias about 14% of the time and that surf is blown out by onshore wind 43% of the time. This is means that we expect 17 days with waves in a typical September, of which 4 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.