The rose diagram shows only the swells directed at Cap Blanc Nez that coincided with light winds or offshore conditions over a normal March. It is based on 1228 predictions, one every 3 hours. The direction of the spokes show where quality surf generating swell comes from. Five colours show increasing wave sizes. The smallest swells, less than 0.5m (1.5 feet), high are coloured blue. Green and yellow illustrate increasing swell sizes and red shows the largest swells, greater than >3m (>10ft). In either graph, the area of any colour is proportional to how frequently that size swell occurs.
The diagram suggests that the most common swell direction, shown by the largest spokes, was NNE, whereas the the most common wind blows from the NW. The chart at the bottom shows the same thing but without direction information. For example, swells larger than 1.5 feet (0.5m) coincided with good wind conditions 7% of the time, equivalent to 2 days. Open sea swells exceeding >3m (>10ft) are unlikely to happen in a normal March. Taking into account the ratio of these swells that coincided with forecast offshore winds we calculate that clean surf can be found at Cap Blanc Nez about 7% of the time and that surf is spoilt by onshore wind 31% of the time. This is means that we expect 12 days with waves in a typical March, of which 2 days should be surfable.
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.