This image shows only the swells directed at Magna Tubes that coincided with light winds or offshore conditions through a typical December. It is based on 1736 predictions, one every 3 hours. The direction of the spokes show where quality surf generating swell comes from. Five colours show increasing wave sizes. The smallest swells, less than 0.5m (1.5 feet), high are coloured blue. Green and yellow show 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 often that size swell was forecast.
The diagram indicates that the most common swell direction, shown by the longest spokes, was SE, whereas the the prevailing wind blows from the SSE. The chart at the bottom shows the same thing but without direction information. For example, swells larger than 1.5 feet (0.5m) coincided with good wind conditions 11% of the time, equivalent to 3 days. Open sea swells exceeding >3m (>10ft) are unlikely to occur in a normal December but 5% of the time we expect swell in the range 2-3m (6.5-10ft) 5%, equivalent to (2 days). Taking into account the fraction of these swells that coincided with forecast offshore winds, and given the fact that Magna Tubes is exposed to open water swells, we calculate that clean surf can be found at Magna Tubes about 11% of the time and that surf is spoilt by onshore wind 28% of the time. This is means that we expect 12 days with waves in a typical December, of which 3 days should be surfable.
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.