Windy Harbour Swell Statistics, Summer: All Swell – Any Wind
This picture describes the combination of swells directed at Windy Harbour over a normal southern hemisphere summer and is based upon 6931 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 optimum grid node based on what we know about Windy Harbour. In this particular case the best grid node is 19 km away (12 miles).
The rose diagram illustrates the distribution of swell sizes and directions, 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 0.9% of the time. Green and yellow show increasing swell sizes and red shows the highest swells, greater than >3m (>10ft). In each graph, the area of any colour is proportional to how commonly that size swell happens.
The diagram implies that the prevailing swell direction, shown by the longest spokes, was SW, whereas the the dominant wind blows from the SSE. Because the wave model grid is offshore, sometimes a strong offshore wind blows largest waves away from Windy Harbour and away from the coast. We combine these with the no surf category of the bar chart. To avoid confusion we don't show these in the rose plot. Because wind determines whether or not waves are surfable at Windy Harbour, you can view an alternative image that shows only the swells that were forecast to coincide with glassy or offshore wind conditions. During a typical southern hemisphere summer, swells large enough to cause good for surfing waves at Windy Harbour run for about 99% 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.