City Beach Groyne Swell Statistics, May: All Swell – Any Wind
The rose diagram shows the range of swells directed at City Beach Groyne through a typical May, based on 1736 NWW3 model predictions since 2007 (values every 3 hours). The wave model does not forecast wind or surf right at the coast so we have chosen the optimum grid node based on what we know about City Beach Groyne. In the case of City Beach Groyne, the best grid node is 24 km away (15 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 were forecast only 0.2% of the time. Green and yellow illustrate increasing swell sizes and red illustrates biggest swells greater than >3m (>10ft). In both graphs, the area of any colour is proportional to how frequently that size swell occurs.
The diagram suggests that the prevailing swell direction, shown by the largest spokes, was WSW, whereas the the prevailing wind blows from the SE. Because the wave model grid is offshore, sometimes a strong offshore wind blows largest waves away from City Beach Groyne 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 plot. Because wind determines whether or not waves are surfable at City Beach Groyne, you can load a different 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 good for surfing 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.