Xa Swell Statistics, May: All Swell – Any Wind

This image describes the variation of swells directed at Xa over a normal May. It is based on 2838 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 Xa. In the case of Xa, the best grid node is 25 km away (16 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 represent increasing wave sizes. Very small swells of less than 0.5m (1.5 feet) high are shown in blue. These happened only 35% of the time. Green and yellow represent increasing swell sizes and red represents the highest 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 ESE, whereas the the dominant wind blows from the SE. Because the wave model grid is out to sea, sometimes a strong offshore wind blows largest waves away from Xa 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 graph. Because wind determines whether or not waves are clean enough to surf at Xa, you can load a different image that shows only the swells that were predicted to coincide with glassy or offshore wind conditions. During a typical May, swells large enough to cause surfable waves at Xa run for about 65% 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.