Arugam Bay Swell Statistics, January: 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 January. It is based on 2372 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 show increasing swell sizes and red illustrates the biggest swells, greater than >3m (>10ft). In either graph, the area of any colour is proportional to how commonly that size swell happens.
The diagram implies that the most common swell direction, shown by the biggest 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 43% of the time, equivalent to 13 days. Open sea swells exceeding >3m (>10ft) are unlikely to arise in a normal January but 25% of the time you can expect swell in the range 1.3-2m (4-6.5ft) 25%, equivalent to (8 days). Taking into account the fraction of these swells that coincided with expected offshore winds, and given the fact that Arugam Bay is exposed to open water swells, we calculate that clean surf can be found at Arugam Bay about 43% of the time and that surf is spoilt by onshore wind 10% of the time. This is means that we expect 16 days with waves in a typical January, of which 13 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.