Aoshima Harbour Swell Statistics, December: All Swell – Any Wind
The graph shows the combination of swells directed at Aoshima Harbour through an average December and is based upon 2457 NWW3 model predictions since 2006 (values every 3 hours). The wave model does not forecast wind or surf right at the coast 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 illustrates the distribution of swell sizes and swell direction, 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 occurred only 33% of the time. Green and yellow show increasing swell sizes and red shows the biggest swells, greater than >3m (>10ft). In each graph, the area of any colour is proportional to how commonly that size swell occurs.
The diagram implies that the prevailing swell direction, shown by the largest spokes, was ESE, whereas the the prevailing wind blows from the NNW. Because the wave model grid is offshore, sometimes a strong offshore wind blows largest waves away from Aoshima 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 graph. Because wind determines whether or not waves are good for surfing at Aoshima Harbour, you can select a similar diagram that shows only the swells that were predicted to coincide with glassy or offshore wind conditions. In a typical December, swells large enough to cause clean enough to surf waves at Aoshima Harbour run for about 67% 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.