Arugam Bay Swell Statistics, Autumn: All Swell – Any Wind
The graph illustrates the variation of swells directed at Arugam Bay over a normal northern hemisphere autumn, based on 7252 NWW3 model predictions since 2006 (values every 3 hours). The wave model does not forecast wind or surf right at the shore so we have chosen the most applicable grid node based on what we know about Arugam Bay. In this particular case 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 lacks 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 happened only 16% of the time. Green and yellow illustrate increasing swell sizes and red represents largest swells greater than >3m (>10ft). In each graph, the area of any colour is proportional to how frequently that size swell occurs.
The diagram suggests that the dominant swell direction, shown by the biggest spokes, was S, whereas the the most common wind blows from the WSW. 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 avoid confusion we don't show these in the rose plot. Because wind determines whether or not waves are surfable at Arugam Bay, you can view an alternative image that shows only the swells that were forecast to coincide with glassy or offshore wind conditions. During a typical northern hemisphere autumn, swells large enough to cause good for surfing waves at Arugam Bay run for about 84% 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.