The rose diagram shows only the swells directed at Keaau that coincided with light winds or offshore conditions over a normal August and is based upon 1736 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 the highest 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 prevailing swell direction, shown by the longest spokes, was NNW, whereas the the dominant 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 5% of the time, equivalent to 2 days. Open sea swells exceeding >3m (>10ft) are unlikely to arise in a normal August. Taking into account the proportion of these swells that coincided with expected offshore winds, and given the fact that Keaau is exposed to open water swells, we calculate that clean surf can be found at Keaau about 5% of the time and that surf is messed up by onshore wind 1.0% of the time. This is means that we expect 2 days with waves in a typical August, of which 2 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.