Arugam Bay Swell Statistics, Spring: All Swell – Any Wind
The figure illustrates the variation of swells directed at Arugam Bay over a normal northern hemisphere spring. It is based on 6580 NWW3 model predictions since 2007 (values every 3 hours). The wave model does not forecast surf and wind right at the coast so we have chosen the best 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 shows the distribution of swell sizes and directions, 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 happened only 0.9% of the time. Green and yellow represent increasing swell sizes and red represents the 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 biggest spokes, was S (which was the same as the most common wind direction). 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 graph. Because wind determines whether or not waves are surfable 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 northern hemisphere spring, swells large enough to cause good for surfing waves at Arugam Bay run for about 99% 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.