K-38 Swell Statistics, September: All Swell – Any Wind
The figure describes the variation of swells directed at K-38 through a typical September, based on 2160 NWW3 model predictions since 2006 (values every 3 hours). The wave model does not forecast wind or surf right at the coastline so we have chosen the best grid node based on what we know about K-38. In the case of K-38, the best grid node is 28 km away (17 miles).
The rose diagram illustrates the distribution of swell sizes and directions, while the graph at the bottom shows the same thing 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 52% of the time. Green and yellow represent increasing swell sizes and red illustrates the highest 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 dominant swell direction, shown by the longest spokes, was WSW, whereas the the dominant wind blows from the NW. Because the wave model grid is offshore, sometimes a strong offshore wind blows largest waves away from K-38 and away from the coast. We combine 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 K-38, 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 September, swells large enough to cause good for surfing waves at K-38 run for about 48% 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.