The rose diagram illustrates the combination of swells directed at Bronte Beach through a typical December. It is based on 1736 NWW3 model predictions since 2006 (values every 3 hours). The wave model does not forecast wind and surf right at the coastline so we have chosen the most applicable grid node based on what we know about Bronte Beach. In the case of Bronte Beach, the best grid node is 23 km away (14 miles).
The rose diagram illustrates the distribution of swell sizes and directions, while the graph at the bottom shows the same thing but 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 31% of the time. Green and yellow show increasing swell sizes and red represents the largest swells, greater than >3m (>10ft). In both graphs, the area of any colour is proportional to how commonly that size swell occurs.
The diagram implies that the most common swell direction, shown by the largest spokes, was SE, whereas the the most common wind blows from the E. Because the wave model grid is out to sea, sometimes a strong offshore wind blows largest waves away from Bronte Beach and offshore. We group these with the no surf category of the bar chart. To simplify things we don't show these in the rose diagram. Because wind determines whether or not waves are good for surfing at Bronte Beach, 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 December, swells large enough to cause clean enough to surf waves at Bronte Beach run for about 69% 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.