Statistiques de Houle pour Airport Lefts, Hiver: Toutes Houles – Tous Vents
The graph describes the variation of swells directed at Airport Lefts over a normal southern hemisphere winter, based on 7266 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 Airport Lefts. In the case of Airport Lefts, the best grid node is 33 km away (21 miles).
The rose diagram describes the distribution of swell sizes and swell direction, 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 occurred only 1.0% of the time. Green and yellow illustrate increasing swell sizes and red represents highest swells greater than >3m (>10ft). In both graphs, the area of any colour is proportional to how often that size swell was forecast.
The diagram indicates that the dominant swell direction, shown by the longest spokes, was SSW, whereas the the dominant wind blows from the ESE. Because the wave model grid is away from the coast, sometimes a strong offshore wind blows largest waves away from Airport Lefts and out to sea. We combine these with the no surf category of the bar chart. To simplify things we don't show these in the rose plot. Because wind determines whether or not waves are good for surfing at Airport Lefts, you can view an alternative image that shows only the swells that were predicted to coincide with glassy or offshore wind conditions. During a typical southern hemisphere winter, swells large enough to cause clean enough to surf waves at Airport Lefts run for about 99% 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.