Arugam Bay Swell Statistics, February: All Swell – Any Wind
This image shows the variation of swells directed at Arugam Bay through a typical February and is based upon 2102 NWW3 model predictions since 2007 (values every 3 hours). The wave model does not forecast surf and wind right at the coastline 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 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 27% of the time. Green and yellow show increasing swell sizes and red represents biggest swells greater than >3m (>10ft). In both graphs, the area of any colour is proportional to how commonly that size swell occurs.
The diagram implies that the dominant swell direction, shown by the largest spokes, was S, whereas the the prevailing wind blows from the NE. Because the wave model grid is out to sea, sometimes a strong offshore wind blows largest waves away from Arugam Bay and offshore. We lump these in 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 clean enough to surf at Arugam Bay, you can view an alternative image that shows only the swells that were expected to coincide with glassy or offshore wind conditions. Over an average February, swells large enough to cause surfable waves at Arugam Bay run for about 73% 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.