Sao Juliao Swell Statistics, All Year: All Swell – Any Wind
The rose diagram describes the combination of swells directed at Sao Juliao through a typical year, based on 26892 NWW3 model predictions since 2006 (values every 3 hours). The wave model does not forecast wind or surf right at the shore so we have chosen the most applicable grid node based on what we know about Sao Juliao. In this particular case the best grid node is 10 km away (6 miles).
The rose diagram describes the distribution of swell directions and swell sizes, while the graph at the bottom shows the same thing but lacks direction information. Five colours show increasing wave sizes. The smallest swells, less than 0.5m (1.5 feet), high are coloured blue. These happened only 16% of the time. Green and yellow represent increasing swell sizes and highest 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 happens.
The diagram implies that the prevailing swell direction, shown by the largest spokes, was WNW, whereas the the dominant wind blows from the NNW. Because the wave model grid is offshore, sometimes a strong offshore wind blows largest waves away from Sao Juliao and away from the coast. We lump these in 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 Sao Juliao, you can select a similar diagram that shows only the swells that were forecast to coincide with glassy or offshore wind conditions. Over an average year, swells large enough to cause clean enough to surf waves at Sao Juliao run for about 84% 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.