Aberffraw Swell Statistics, All Year: All Swell – Any Wind
This chart shows the variation of swells directed at Aberffraw through an average year, based on 28036 NWW3 model predictions since 2006 (values every 3 hours). The wave model does not forecast wind and surf right at the coastline so we have chosen the best grid node based on what we know about Aberffraw. In this particular case the best grid node is 20 km away (12 miles).
The rose diagram describes the distribution of swell sizes and swell direction, while the graph at the bottom shows the same thing but 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 55% of the time. Green and yellow illustrate increasing swell sizes and biggest swells greater than >3m (>10ft) are shown in red. In either 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 longest spokes, was SW, whereas the the prevailing wind blows from the WSW. Because the wave model grid is offshore, sometimes a strong offshore wind blows largest waves away from Aberffraw and away from the coast. We lump these in 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 Aberffraw, you can load a different image that shows only the swells that were expected to coincide with glassy or offshore wind conditions. In a typical year, swells large enough to cause surfable waves at Aberffraw run for about 45% 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.