Praia da Leirosa Swell Statistics, April: All Swell – Any Wind
The rose diagram illustrates the range of swells directed at Praia da Leirosa over a normal April. It is based on 1680 NWW3 model predictions since 2007 (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 Praia da Leirosa, and at Praia da Leirosa the best grid node is 11 km away (7 miles).
The rose diagram illustrates the distribution of swell sizes and swell direction, while the graph at the bottom shows the same thing without direction information. Five colours illustrate increasing wave sizes. Blue shows the smallest swells, less that 0.5m (1.5 feet) high. These happened only 7% of the time. Green and yellow show increasing swell sizes and red represents the largest swells, greater than >3m (>10ft). In each graph, the area of any colour is proportional to how often that size swell happens.
The diagram indicates that the most common swell direction, shown by the biggest 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 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 clean enough to surf at Praia da Leirosa, you can select a similar diagram that shows only the swells that were expected 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 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.