Arrifana Swell Statistics, Fevereiro: 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 February. It is based on 2102 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 biggest swells greater than >3m (>10ft) are shown in red. In each graph, the area of any colour is proportional to how often that size swell occurs.
The diagram indicates that the prevailing swell direction, shown by the longest spokes, was WNW, whereas the the prevailing wind blows from the NNW. 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 36% of the time, equivalent to 10 days. Open water swells exceeding >3m (>10ft) only happen 3% of the time in a typical February, equivalent to just one day but 17% of the time we expect swell in the range 2-3m (6.5-10ft) 17%, equivalent to (5 days). Taking into account the ratio of these swells that coincided with forecast offshore winds, and given the fact that Arrifana is slightly protected from open water swells, we think that that clean surf can be found at Arrifana about 36% of the time and that surf is spoilt by onshore wind 43% of the time. This is means that we expect 22 days with waves in a typical February, of which 10 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.