The figure illustrates the range of swells directed at Hells Mouth (Porth Neigwl) through a typical August, based on 1735 NWW3 model predictions since 2006 (values every 3 hours). The wave model does not forecast surf and wind right at the coastline so we have chosen the most applicable grid node based on what we know about Hells Mouth (Porth Neigwl), and at Hells Mouth (Porth Neigwl) the best grid node is 36 km away (22 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 41% of the time. Green and yellow show increasing swell sizes and red illustrates largest swells greater than >3m (>10ft). In each graph, the area of any colour is proportional to how frequently that size swell occurs.
The diagram suggests that the dominant swell direction, shown by the biggest spokes, was WSW (which was the same as the most common wind direction). Because the wave model grid is away from the coast, sometimes a strong offshore wind blows largest waves away from Hells Mouth (Porth Neigwl) 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 clean enough to surf at Hells Mouth (Porth Neigwl), you can select a similar diagram that shows only the swells that were forecast to coincide with glassy or offshore wind conditions. Over an average August, swells large enough to cause surfable waves at Hells Mouth (Porth Neigwl) run for about 59% 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.