Arrifana Swell Statistics, Winter: Surf with Light or Offshore Winds
This image shows only the swells directed at Arrifana that coincided with light winds or offshore conditions over a normal northern hemisphere winter. It is based on 6931 predictions, one every 3 hours. The direction of the spokes show where quality surf generating swell comes from. Five colours show increasing wave sizes. The smallest swells, less than 0.5m (1.5 feet), high are coloured blue. Green and yellow show increasing swell sizes and red shows largest 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 most common swell direction, shown by the biggest spokes, was WNW, whereas the the most common wind blows from the N. 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 40% of the time, equivalent to 36 days. Expect open water swells to exceed >3m (>10ft) 3% of the time (3 days). Taking into account the proportion of these swells that coincided with forecast offshore winds, and given the fact that Arrifana is slightly protected from open water swells, we estimate that clean surf can be found at Arrifana about 40% of the time and that surf is spoilt by onshore wind 42% of the time. This is means that we expect 75 days with waves in a typical northern hemisphere winter, of which 36 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.