Gyllyngvase Beach Swell Statistics, May: All Swell – Any Wind
The rose diagram shows the variation of swells directed at Gyllyngvase Beach through an average May and is based upon 1985 NWW3 model predictions since 2007 (values every 3 hours). The wave model does not forecast wind or surf right at the coastline so we have chosen the best grid node based on what we know about Gyllyngvase Beach. In this particular case the best grid node is 16 km away (10 miles).
The rose diagram describes the distribution of swell sizes and directions, 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 occurred only 93% of the time. Green and yellow show increasing swell sizes and red represents biggest swells greater than >3m (>10ft). In each 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 largest spokes, was SSE, whereas the the prevailing wind blows from the WNW. Because the wave model grid is out to sea, sometimes a strong offshore wind blows largest waves away from Gyllyngvase Beach and offshore. We lump these in with the no surf category of the bar chart. To keep it simple we don't show these in the rose plot. Because wind determines whether or not waves are surfable at Gyllyngvase Beach, you can select a similar diagram that shows only the swells that were predicted to coincide with glassy or offshore wind conditions. In a typical May, swells large enough to cause good for surfing waves at Gyllyngvase Beach run for about 1.0% 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.