Ampang Swell Statistics, Autumn: Surf with Light or Offshore Winds
This image shows only the swells directed at Ampang that coincided with light winds or offshore conditions through a typical southern hemisphere autumn. It is based on 6580 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 illustrate increasing swell sizes and red shows biggest 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 prevailing swell direction, shown by the largest spokes, was SSW, whereas the the prevailing wind blows from the ESE. 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 26% of the time, equivalent to 24 days. Open sea swells exceeding >3m (>10ft) are unlikely to happen in a normal southern hemisphere autumn but 4% of the time we expect swell in the range 2-3m (6.5-10ft) 4%, equivalent to (4 days). Taking into account the proportion of these swells that coincided with predicted offshore winds, and given the fact that Ampang is slightly protected from open water swells, we estimate that clean surf can be found at Ampang about 26% of the time and that surf is blown out by onshore wind 35% of the time. This is means that we expect 56 days with waves in a typical southern hemisphere autumn, of which 24 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.