Arugam Bay Swell Statistics, January: All Swell – Any Wind
This picture shows the variation of swells directed at Arugam Bay over a normal January, based on 2372 NWW3 model predictions since 2007 (values every 3 hours). The wave model does not forecast surf and wind right at the shore so we have chosen the optimum grid node based on what we know about Arugam Bay. In the case of Arugam Bay, the best grid node is 42 km away (26 miles).
The rose diagram describes the distribution of swell sizes and directions, while the graph at the bottom shows the same thing but without direction information. Five colours show increasing wave sizes. The smallest swells, less than 0.5m (1.5 feet), high are coloured blue. These occurred only 47% of the time. Green and yellow illustrate increasing swell sizes and red represents 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. Because the wave model grid is out to sea, sometimes a strong offshore wind blows largest waves away from Arugam Bay and offshore. We group these with the no surf category of the bar chart. To avoid confusion we don't show these in the rose plot. Because wind determines whether or not waves are good for surfing at Arugam Bay, you can load a different image that shows only the swells that were predicted to coincide with glassy or offshore wind conditions. During a typical January, swells large enough to cause clean enough to surf waves at Arugam Bay run for about 53% of the time.
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.