Castles Swell Statistics, March: All Swell – Any Wind
The rose diagram illustrates the combination of swells directed at Castles through an average March, based on 1972 NWW3 model predictions since 2007 (values every 3 hours). The wave model does not forecast wind and surf right at the coast so we have chosen the optimum grid node based on what we know about Castles. In the case of Castles, the best grid node is 32 km away (20 miles).
The rose diagram describes the distribution of swell sizes and swell direction, while the graph at the bottom shows the same thing but lacks direction information. Five colours illustrate increasing wave sizes. Blue shows the smallest swells, less that 0.5m (1.5 feet) high. These occurred only 35% of the time. Green and yellow represent increasing swell sizes and red illustrates the largest swells, greater than >3m (>10ft). In each graph, the area of any colour is proportional to how commonly that size swell happens.
The diagram implies that the dominant swell direction, shown by the longest spokes, was SE, whereas the the most common wind blows from the NW. Because the wave model grid is out to sea, sometimes a strong offshore wind blows largest waves away from Castles and offshore. We combine these 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 Castles, 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 March, swells large enough to cause surfable waves at Castles run for about 65% 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.