The graph shows the combination of swells directed at Le Letty over a normal July, based on 1736 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 most applicable grid node based on what we know about Le Letty. In the case of Le Letty, the best grid node is 34 km away (21 miles).
The rose diagram describes the distribution of swell directions and swell sizes, while the graph at the bottom shows the same thing without direction information. Five colours illustrate increasing wave sizes. Blue shows the smallest swells, less that 0.5m (1.5 feet) high. These were forecast only 23% of the time. Green and yellow represent increasing swell sizes and red illustrates the biggest 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 longest spokes, was W (which was the same as the prevailing wind direction). Because the wave model grid is away from the coast, sometimes a strong offshore wind blows largest waves away from Le Letty and out to sea. We lump these in with the no surf category of the bar chart. To keep it simple we don't show these in the rose plot. Because wind determines whether or not waves are surfable at Le Letty, you can view an alternative image that shows only the swells that were expected to coincide with glassy or offshore wind conditions. During a typical July, swells large enough to cause good for surfing waves at Le Letty run for about 77% 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.