San Miguel - Areias Swell Statistics, December: Surf with Light or Offshore Winds
The rose diagram shows only the swells directed at San Miguel - Areias that coincided with light winds or offshore conditions over a normal December. It is based on 2457 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 shows the biggest 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 longest spokes, was NW, whereas the the prevailing wind blows from the SW. 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 30% of the time, equivalent to 9 days. Expect open water swells to exceed >3m (>10ft) 5% of the time (2 days). Taking into account the fraction 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 calculate that clean surf can be found at San Miguel - Areias about 30% of the time and that surf is blown out by onshore wind 41% of the time. This is means that we expect 21 days with waves in a typical December, of which 9 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.