Prainha Surf Stats

The figure describes the variation of swells directed at Prainha over a normal October and is based upon 3471 NWW3 model predictions since 2006 (values every 3 hours). The wave model does not forecast wind or surf right at the coastline so we have chosen the optimum grid node based on what we know about Prainha. In the case of Prainha, the best grid node is 26 km away (16 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 77% of the time. Green and yellow show increasing swell sizes and red shows the highest 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 prevailing swell direction, shown by the biggest spokes, was SE, whereas the the dominant wind blows from the ESE. Because the wave model grid is offshore, sometimes a strong offshore wind blows largest waves away from Prainha and away from the coast. We combine these with the no surf category of the bar chart. To keep it simple we don't show these in the rose graph. Because wind determines whether or not waves are good for surfing at Prainha, you can view an alternative 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 clean enough to surf waves at Prainha run for about 23% of the time.

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