Abereiddy Swell Statistics, Spring: All Swell – Any Wind
This picture shows the combination of swells directed at Abereiddy over a normal northern hemisphere spring and is based upon 6580 NWW3 model predictions since 2007 (values every 3 hours). The wave model does not forecast surf and wind right at the coast so we have chosen the most applicable grid node based on what we know about Abereiddy. In this particular case the best grid node is 21 km away (13 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 represent increasing wave sizes. Very small swells of less than 0.5m (1.5 feet) high are shown in blue. These happened 34% of the time. Green and yellow show increasing swell sizes and biggest swells greater than >3m (>10ft) are shown in red. In both graphs, the area of any colour is proportional to how commonly that size swell was forecast.
The diagram implies that the dominant swell direction, shown by the longest spokes, was WSW, whereas the the prevailing wind blows from the W. Because the wave model grid is away from the coast, sometimes a strong offshore wind blows largest waves away from Abereiddy and out to sea. We group these with the no surf category of the bar chart. To keep it simple we don't show these in the rose graph. Because wind determines whether or not waves are good for surfing at Abereiddy, you can select a similar diagram that shows only the swells that were forecast to coincide with glassy or offshore wind conditions. During a typical northern hemisphere spring, swells large enough to cause clean enough to surf waves at Abereiddy run for about 31% 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.