Arugam Bay Swell Statistics, August: All Swell – Any Wind
This chart illustrates the combination of swells directed at Arugam Bay through an average August. It is based on 2480 NWW3 model predictions since 2006 (values every 3 hours). The wave model does not forecast surf and wind right at the coastline 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 swell direction, while the graph at the bottom shows the same thing but without direction information. Five colours represent increasing wave sizes. Very small swells of less than 0.5m (1.5 feet) high are shown in blue. These occurred only 0% of the time. Green and yellow illustrate increasing swell sizes and red shows largest swells greater than >3m (>10ft). In each 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 S, whereas the the most common wind blows from the SW. Because the wave model grid is away from the coast, sometimes a strong offshore wind blows largest waves away from Arugam Bay and out to sea. We combine these with the no surf category of the bar chart. To simplify things 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 expected to coincide with glassy or offshore wind conditions. In a typical August, swells large enough to cause clean enough to surf waves at Arugam Bay run for about 100% 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.