Praia da Leirosa Swell Statistics, April: All Swell – Any Wind
This chart illustrates the variation of swells directed at Praia da Leirosa over a normal April, based on 2160 NWW3 model predictions since 2007 (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 Praia da Leirosa. In the case of Praia da Leirosa, the best grid node is 11 km away (7 miles).
The rose diagram shows 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 occurred only 5% of the time. Green and yellow represent increasing swell sizes and red illustrates the largest swells, greater than >3m (>10ft). In both graphs, 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 largest spokes, was WNW, whereas the the most common wind blows from the NNW. Because the wave model grid is offshore, sometimes a strong offshore wind blows largest waves away from Praia da Leirosa and away from the coast. We combine these with the no surf category of the bar chart. To simplify things we don't show these in the rose diagram. Because wind determines whether or not waves are clean enough to surf at Praia da Leirosa, you can load a different image that shows only the swells that were forecast to coincide with glassy or offshore wind conditions. During a typical April, swells large enough to cause surfable waves at Praia da Leirosa run for about 95% 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.