The graph shows the variation of swells directed at The Cut-Nelson Harbour over a normal southern hemisphere summer, based on 3608 NWW3 model predictions since 2008 (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 The Cut-Nelson Harbour. In the case of The Cut-Nelson Harbour, the best grid node is 35 km away (22 miles).
The rose diagram describes the distribution of swell sizes and directions, while the graph at the bottom shows the same thing but lacks direction information. Five colours show increasing wave sizes. The smallest swells, less than 0.5m (1.5 feet), high are coloured blue. These happened 55% of the time. Green and yellow illustrate increasing swell sizes and red represents biggest swells greater than >3m (>10ft). In both graphs, the area of any colour is proportional to how often that size swell happens.
The diagram indicates that the prevailing swell direction, shown by the longest spokes, was NNW (which was the same as the prevailing wind direction). Because the wave model grid is offshore, sometimes a strong offshore wind blows largest waves away from The Cut-Nelson Harbour and away from the coast. We lump these in 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 clean enough to surf at The Cut-Nelson Harbour, you can load a different image that shows only the swells that were predicted to coincide with glassy or offshore wind conditions. During a typical southern hemisphere summer, swells large enough to cause surfable waves at The Cut-Nelson Harbour run for about 12% 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.