The graph describes the variation of swells directed at Lightning Bolt through an average northern hemisphere spring and is based upon 4850 NWW3 model predictions since 2007 (values every 3 hours). The wave model does not forecast wind or surf right at the coast so we have chosen the most applicable grid node based on what we know about Lightning Bolt, and at Lightning Bolt the best grid node is 15 km away (9 miles).
The rose diagram describes the distribution of swell sizes and directions, while the graph at the bottom shows the same thing 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 52% of the time. Green and yellow represent increasing swell sizes and red represents highest swells greater than >3m (>10ft). In both graphs, the area of any colour is proportional to how often that size swell occurs.
The diagram indicates that the most common swell direction, shown by the largest spokes, was ESE, whereas the the dominant wind blows from the E. Because the wave model grid is out to sea, sometimes a strong offshore wind blows largest waves away from Lightning Bolt and offshore. We lump these in 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 Lightning Bolt, you can select a similar diagram that shows only the swells that were expected to coincide with glassy or offshore wind conditions. In a typical northern hemisphere spring, swells large enough to cause good for surfing waves at Lightning Bolt run for about 48% 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.