City Beach Groyne Swell Statistics, May: All Swell – Any Wind
The figure shows the variation of swells directed at City Beach Groyne through a typical May. It is based on 1910 NWW3 model predictions since 2007 (values every 3 hours). The wave model does not forecast wind and surf right at the shore so we have chosen the optimum grid node based on what we know about City Beach Groyne, and at City Beach Groyne the best grid node is 24 km away (15 miles).
The rose diagram illustrates the distribution of swell directions and swell sizes, while the graph at the bottom shows the same thing without direction information. Five colours show increasing wave sizes. The smallest swells, less than 0.5m (1.5 feet), high are coloured blue. These were forecast only 0.3% of the time. Green and yellow show increasing swell sizes and red represents the biggest swells, greater than >3m (>10ft). In either graph, the area of any colour is proportional to how often that size swell was forecast.
The diagram indicates that the dominant swell direction, shown by the largest spokes, was WSW, whereas the the prevailing wind blows from the SE. Because the wave model grid is away from the coast, sometimes a strong offshore wind blows largest waves away from City Beach Groyne 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 City Beach Groyne, you can view an alternative image that shows only the swells that were forecast to coincide with glassy or offshore wind conditions. Over an average May, swells large enough to cause surfable waves at City Beach Groyne run for about 91% 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.