This picture illustrates the range of swells directed at Playa de Arnao through an average year, based on 20068 NWW3 model predictions since 2006 (values every 3 hours). The wave model does not forecast surf and wind right at the shore so we have chosen the optimum grid node based on what we know about Playa de Arnao. In the case of Playa de Arnao, the best grid node is 47 km away (29 miles).
The rose diagram shows the distribution of swell directions and swell sizes, while the graph at the bottom shows the same thing but 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 occurred only 10% of the time. Green and yellow represent increasing swell sizes and red illustrates largest swells greater than >3m (>10ft). In either graph, the area of any colour is proportional to how frequently that size swell happens.
The diagram suggests that the prevailing swell direction, shown by the biggest spokes, was NW, whereas the the most common wind blows from the NNW. Because the wave model grid is out to sea, sometimes a strong offshore wind blows largest waves away from Playa de Arnao and offshore. We group these 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 good for surfing at Playa de Arnao, 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 year, swells large enough to cause clean enough to surf waves at Playa de Arnao run for about 90% 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.