Ampang Swell Statistics, Summer: 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 summer. It is based on 6931 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 largest swells greater than >3m (>10ft) are shown in red. In each 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 biggest spokes, was SSW, whereas the the most common 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 44% of the time, equivalent to 40 days. Open sea swells exceeding >3m (>10ft) are unlikely to arise in a normal southern hemisphere summer but 8% of the time we expect swell in the range 2-3m (6.5-10ft) 8%, equivalent to (7 days). Taking into account the ratio of these swells that coincided with forecast offshore winds, and given the fact that Ampang is slightly protected from open water swells, we calculate that clean surf can be found at Ampang about 44% of the time and that surf is messed up by onshore wind 9% of the time. This is means that we expect 48 days with waves in a typical southern hemisphere summer, of which 40 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.