K38 and 39 Swell Statistics, September: All Swell – Any Wind
This picture describes the variation of swells directed at K38 and 39 over a normal September. It is based on 1920 NWW3 model predictions since 2006 (values every 3 hours). The wave model does not forecast surf and wind right at the coast so we have chosen the optimum grid node based on what we know about K38 and 39. In the case of K38 and 39, the best grid node is 41 km away (25 miles).
The rose diagram shows 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 16% of the time. Green and yellow show increasing swell sizes and red represents the highest swells, greater than >3m (>10ft). In each graph, the area of any colour is proportional to how often that size swell occurs.
The diagram indicates that the dominant swell direction, shown by the largest spokes, was SSE, whereas the the dominant wind blows from the W. Because the wave model grid is offshore, sometimes a strong offshore wind blows largest waves away from K38 and 39 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 surfable at K38 and 39, you can select a similar diagram that shows only the swells that were predicted to coincide with glassy or offshore wind conditions. During a typical September, swells large enough to cause good for surfing waves at K38 and 39 run for about 33% 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.