Barre de Balizas Swell Statistics, Winter: Surf with Light or Offshore Winds
The rose diagram shows only the swells directed at Barre de Balizas that coincided with light winds or offshore conditions through a typical southern hemisphere winter and is based upon 5802 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 illustrate increasing swell sizes and biggest swells greater than >3m (>10ft) are shown in red. In either graph, the area of any colour is proportional to how commonly that size swell happens.
The diagram implies that the dominant swell direction, shown by the longest spokes, was SE, whereas the the prevailing 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 32% of the time, equivalent to 29 days. Open sea swells exceeding >3m (>10ft) are unlikely to arise in a normal southern hemisphere winter but 3% of the time we expect swell in the range 2-3m (6.5-10ft) 3%, equivalent to (3 days). Taking into account the fraction of these swells that coincided with expected offshore winds, and given the fact that Barre de Balizas is exposed to open water swells, we estimate that clean surf can be found at Barre de Balizas about 32% of the time and that surf is spoilt by onshore wind 42% of the time. This is means that we expect 67 days with waves in a typical southern hemisphere winter, of which 29 days should be clean enough to surf.
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.