Ahu Ahu Road Swell Statistics, May: Surf with Light or Offshore Winds
The rose diagram shows only the swells directed at Ahu Ahu Road that coincided with light winds or offshore conditions over a normal May. It is based on 2200 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 shows the highest swells, greater than >3m (>10ft). In each graph, the area of any colour is proportional to how frequently that size swell was forecast.
The diagram suggests that the dominant swell direction, shown by the biggest spokes, was WSW (which was the same as the dominant wind direction). 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 35% of the time, equivalent to 11 days. Open sea swells exceeding >3m (>10ft) are unlikely to occur in a normal May but 9% of the time we expect swell in the range 2-3m (6.5-10ft) 9%, equivalent to (3 days). Taking into account the fraction of these swells that coincided with expected offshore winds, and given the fact that Ahu Ahu Road is exposed to open water swells, we calculate that clean surf can be found at Ahu Ahu Road about 35% of the time and that surf is spoilt by onshore wind 57% of the time. This is means that we expect 29 days with waves in a typical May, of which 11 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.