Cassino Swell Statistics, December: All Swell – Any Wind
The graph describes the variation of swells directed at Cassino through a typical December. It is based on 1961 NWW3 model predictions since 2006 (values every 3 hours). The wave model does not forecast surf and wind right at the coastline so we have chosen the optimum grid node based on what we know about Cassino, and at Cassino the best grid node is 37 km away (23 miles).
The rose diagram shows the distribution of swell sizes and directions, 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 were forecast only 61% of the time. Green and yellow represent increasing swell sizes and highest swells greater than >3m (>10ft) are shown in red. In each graph, the area of any colour is proportional to how commonly that size swell was forecast.
The diagram implies that the prevailing swell direction, shown by the biggest spokes, was SSE, whereas the the dominant wind blows from the E. Because the wave model grid is offshore, sometimes a strong offshore wind blows largest waves away from Cassino 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 plot. Because wind determines whether or not waves are clean enough to surf at Cassino, you can select a similar diagram that shows only the swells that were forecast to coincide with glassy or offshore wind conditions. Over an average December, swells large enough to cause surfable waves at Cassino run for about 39% 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.