Arrieta Swell Statistics, December: Surf with Light or Offshore Winds
This image shows only the swells directed at Arrieta 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 represent increasing wave sizes. Very small swells of less than 0.5m (1.5 feet) high are shown in blue. Green and yellow show increasing swell sizes and red represents largest swells greater than >3m (>10ft). In both graphs, the area of any colour is proportional to how frequently that size swell happens.
The diagram suggests that the most common swell direction, shown by the longest spokes, was NW, whereas the the most common wind blows from the ENE. 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 3% of the time, equivalent to 1 days. Open sea swells exceeding >3m (>10ft) are unlikely to arise in a normal December. Taking into account the fraction of these swells that coincided with forecast offshore winds, and given the fact that Arrieta is quite sheltered from open water swells, we estimate that clean surf can be found at Arrieta about 3% of the time and that surf is messed up by onshore wind 34% of the time. This is means that we expect 11 days with waves in a typical December, of which 1 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.