Statistiques de Surf de St Jean de Monts

This picture illustrates the combination of swells directed at St Jean de Monts over a normal October. It is based on 3471 NWW3 model predictions since 2006 (values every 3 hours). The wave model does not forecast wind and surf right at the shore so we have chosen the best grid node based on what we know about St Jean de Monts, and at St Jean de Monts the best grid node is 31 km away (19 miles). The rose diagram illustrates the distribution of swell directions and swell sizes, while the graph at the bottom shows the same thing but lacks direction information. Five colours illustrate increasing wave sizes. Blue shows the smallest swells, less that 0.5m (1.5 feet) high. These happened only 10% of the time. Green and yellow illustrate increasing swell sizes and largest swells greater than >3m (>10ft) are shown in red. In either graph, the area of any colour is proportional to how commonly that size swell was forecast. The diagram implies that the dominant swell direction, shown by the biggest spokes, was W, whereas the the most common wind blows from the SE. Because the wave model grid is out to sea, sometimes a strong offshore wind blows largest waves away from St Jean de Monts 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 clean enough to surf at St Jean de Monts, you can load a different image that shows only the swells that were expected to coincide with glassy or offshore wind conditions. During a typical October, swells large enough to cause surfable waves at St Jean de Monts run for about 90% of the time.

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