Aoshima Harbour Swell Statistics, December: All Swell – Any Wind
This picture shows the combination of swells directed at Aoshima Harbour through a typical December and is based upon 2209 NWW3 model predictions since 2006 (values every 3 hours). The wave model does not forecast wind and surf right at the shore so we have chosen the best grid node based on what we know about Aoshima Harbour. In the case of Aoshima Harbour, the best grid node is 33 km away (21 miles).
The rose diagram describes the distribution of swell sizes and swell direction, while the graph at the bottom shows the same thing without 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 occurred only 36% of the time. Green and yellow represent increasing swell sizes and biggest swells greater than >3m (>10ft) are shown in red. In both graphs, the area of any colour is proportional to how frequently that size swell occurs.
The diagram suggests that the dominant swell direction, shown by the largest spokes, was ESE, whereas the the prevailing wind blows from the NNW. Because the wave model grid is away from the coast, sometimes a strong offshore wind blows largest waves away from Aoshima Harbour 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 diagram. Because wind determines whether or not waves are surfable at Aoshima Harbour, you can view an alternative image that shows only the swells that were predicted to coincide with glassy or offshore wind conditions. Over an average December, swells large enough to cause good for surfing waves at Aoshima Harbour run for about 64% 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.