Army Beach Swell Statistics, Janeiro: All Swell – Any Wind
This picture shows the range of swells directed at Army Beach through a typical January, based on 2372 NWW3 model predictions since 2007 (values every 3 hours). The wave model does not forecast surf and wind right at the coastline so we have chosen the most applicable grid node based on what we know about Army Beach. In the case of Army Beach, the best grid node is 32 km away (20 miles).
The rose diagram illustrates 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 12% of the time. Green and yellow illustrate increasing swell sizes and biggest 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 happens.
The diagram implies that the prevailing swell direction, shown by the biggest spokes, was NW, whereas the the prevailing wind blows from the ENE. Because the wave model grid is away from the coast, sometimes a strong offshore wind blows largest waves away from Army Beach and out to sea. We group these with the no surf category of the bar chart. To simplify things we don't show these in the rose graph. Because wind determines whether or not waves are surfable at Army Beach, you can view an alternative image that shows only the swells that were expected to coincide with glassy or offshore wind conditions. Over an average January, swells large enough to cause good for surfing waves at Army Beach run for about 88% 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.