This image shows only the swells directed at Steamer Lane-The Slot that coincided with light winds or offshore conditions over a normal northern hemisphere winter. It is based on 5048 predictions, one every 3 hours. The direction of the spokes show where quality surf generating swell comes from. Five colours represent increasing wave sizes. Very small swells of less than 0.5m (1.5 feet) high are shown in blue. 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 often that size swell happens.
The diagram indicates that the prevailing swell direction, shown by the longest spokes, was WNW, whereas the the prevailing wind blows from the N. 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 43% of the time, equivalent to 39 days. Expect open water swells to exceed >3m (>10ft) 5% of the time (5 days). Taking into account the ratio of these swells that coincided with predicted offshore winds, and given the fact that Steamer Lane-The Slot is slightly protected from open water swells, we think that that clean surf can be found at Steamer Lane-The Slot about 43% of the time and that surf is spoilt by onshore wind 52% of the time. This is means that we expect 86 days with waves in a typical northern hemisphere winter, of which 39 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.