Statistiques de Houle pour ADs/Doubles, Mars: Toutes Houles – Tous Vents
The figure illustrates the variation of swells directed at ADs/Doubles through an average March. It is based on 2220 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 best grid node based on what we know about ADs/Doubles. In this particular case the best grid node is 28 km away (17 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 represent increasing wave sizes. Very small swells of less than 0.5m (1.5 feet) high are shown in blue. These were forecast only 67% of the time. Green and yellow represent increasing swell sizes and red represents largest swells greater than >3m (>10ft). In each graph, the area of any colour is proportional to how commonly that size swell happens.
The diagram implies that the most common swell direction, shown by the largest spokes, was E, whereas the the most common wind blows from the ENE. Because the wave model grid is away from the coast, sometimes a strong offshore wind blows largest waves away from ADs/Doubles 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 ADs/Doubles, you can select a similar diagram that shows only the swells that were forecast to coincide with glassy or offshore wind conditions. In a typical March, swells large enough to cause good for surfing waves at ADs/Doubles run for about 33% 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.