This image shows only the swells directed at Sanur Reef that coincided with light winds or offshore conditions over a normal September. It is based on 1680 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 represent increasing swell sizes and red represents highest swells greater than >3m (>10ft). In either graph, the area of any colour is proportional to how commonly that size swell occurs.
The diagram implies that the dominant swell direction, shown by the longest spokes, was SSW, whereas the the dominant wind blows from the SE. 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 8% of the time, equivalent to 2 days. Open sea swells exceeding >3m (>10ft) are unlikely to happen in a normal September but 8% of the time we expect swell in the range 2-3m (6.5-10ft) 8%, equivalent to (2 days). Taking into account the fraction of these swells that coincided with expected offshore winds, and given the fact that Sanur Reef is quite sheltered from open water swells, we estimate that clean surf can be found at Sanur Reef about 8% of the time and that surf is spoilt by onshore wind 59% of the time. This is means that we expect 20 days with waves in a typical September, 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.