This image shows only the swells directed at Barrinha that coincided with light winds or offshore conditions over a normal southern hemisphere winter. It is based on 5066 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 illustrates the largest swells, greater than >3m (>10ft). In either graph, the area of any colour is proportional to how frequently that size swell happens.
The diagram suggests that the dominant swell direction, shown by the longest spokes, was SSE, 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 27% of the time, equivalent to 25 days. Open sea swells exceeding >3m (>10ft) are unlikely to arise in a normal southern hemisphere winter but 12% of the time we expect swell in the range 2-3m (6.5-10ft) 12%, equivalent to (11 days). Taking into account the fraction of these swells that coincided with forecast offshore winds, and given the fact that Barrinha is slightly protected from open water swells, we think that that clean surf can be found at Barrinha about 27% of the time and that surf is messed up by onshore wind 25% of the time. This is means that we expect 47 days with waves in a typical southern hemisphere winter, of which 25 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.