Arrieta Swell Statistics, Summer: All Swell – Any Wind
The graph describes the variation of swells directed at Arrieta through a typical northern hemisphere summer and is based upon 7266 NWW3 model predictions since 2006 (values every 3 hours). The wave model does not forecast wind or surf right at the coast so we have chosen the most applicable grid node based on what we know about Arrieta, and at Arrieta the best grid node is 41 km away (25 miles).
The rose diagram describes the distribution of swell sizes and swell direction, while the graph at the bottom shows the same thing but lacks 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 happened only 3% of the time. Green and yellow represent 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 frequently that size swell happens.
The diagram suggests that the most common swell direction, shown by the longest spokes, was N (which was the same as the dominant wind direction). Because the wave model grid is out to sea, sometimes a strong offshore wind blows largest waves away from Arrieta and offshore. We combine these with the no surf category of the bar chart. To simplify things we don't show these in the rose plot. Because wind determines whether or not waves are clean enough to surf at Arrieta, you can load a different image that shows only the swells that were predicted to coincide with glassy or offshore wind conditions. Over an average northern hemisphere summer, swells large enough to cause surfable waves at Arrieta run for about 22% 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.