Arugam Bay Swell Statistics, Winter: Surf with Light or Offshore Winds
This image shows only the swells directed at Arugam Bay that coincided with light winds or offshore conditions through a typical northern hemisphere winter. 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 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 biggest swells, greater than >3m (>10ft). In either graph, the area of any colour is proportional to how often that size swell occurs.
The diagram indicates that the dominant swell direction, shown by the largest spokes, was S, whereas the the prevailing wind blows from the NNE. 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 40% of the time, equivalent to 36 days. Open sea swells exceeding >3m (>10ft) are unlikely to happen in a normal northern hemisphere winter but 18% of the time you can expect swell in the range 1.3-2m (4-6.5ft) 18%, equivalent to (16 days). Taking into account the proportion of these swells that coincided with forecast offshore winds, and given the fact that Arugam Bay is exposed to open water swells, we estimate that clean surf can be found at Arugam Bay about 40% of the time and that surf is blown out by onshore wind 18% of the time. This is means that we expect 53 days with waves in a typical northern hemisphere winter, of which 36 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.