This picture illustrates the range of swells directed at Playa de Rio Sieira/Furnas through a typical July and is based upon 1736 NWW3 model predictions since 2006 (values every 3 hours). The wave model does not forecast wind and surf right at the coastline so we have chosen the optimum grid node based on what we know about Playa de Rio Sieira/Furnas. In the case of Playa de Rio Sieira/Furnas, the best grid node is 15 km away (9 miles).
The rose diagram describes the distribution of swell sizes and swell direction, while the graph at the bottom shows the same thing without direction information. Five colours show increasing wave sizes. The smallest swells, less than 0.5m (1.5 feet), high are coloured blue. These occurred only 7% of the time. Green and yellow illustrate increasing swell sizes and red shows the largest swells, greater than >3m (>10ft). In both graphs, the area of any colour is proportional to how commonly that size swell was forecast.
The diagram implies that the most common swell direction, shown by the longest spokes, was WNW, whereas the the most common wind blows from the NW. Because the wave model grid is away from the coast, sometimes a strong offshore wind blows largest waves away from Playa de Rio Sieira/Furnas and out to sea. We lump these in with the no surf category of the bar chart. To avoid confusion we don't show these in the rose plot. Because wind determines whether or not waves are surfable at Playa de Rio Sieira/Furnas, you can view an alternative image that shows only the swells that were expected to coincide with glassy or offshore wind conditions. Over an average July, swells large enough to cause good for surfing waves at Playa de Rio Sieira/Furnas run for about 93% 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.