Aticama Swell Statistics, Setembro: Surf with Light or Offshore Winds
The rose diagram shows only the swells directed at Aticama that coincided with light winds or offshore conditions through a typical September and is based upon 2400 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 red represents largest swells greater than >3m (>10ft). In both graphs, the area of any colour is proportional to how commonly that size swell was forecast.
The diagram implies that the prevailing swell direction, shown by the longest spokes, was SSW, 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 55% of the time, equivalent to 16 days. Open sea swells exceeding >3m (>10ft) are unlikely to occur in a normal September but 11% of the time you can expect swell in the range 1.3-2m (4-6.5ft) 11%, equivalent to (3 days). Taking into account the fraction of these swells that coincided with expected offshore winds, and given the fact that Aticama is exposed to open water swells, we estimate that clean surf can be found at Aticama about 55% of the time and that surf is messed up by onshore wind 37% of the time. This is means that we expect 28 days with waves in a typical September, of which 16 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.