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Usami Swell Statistics, All Year: Surf with Light or Offshore Winds

This image shows only the swells directed at Usami that coincided with light winds or offshore conditions through a typical year. It is based on 33252 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 either graph, the area of any colour is proportional to how commonly that size swell was forecast.

The diagram implies that the dominant swell direction, shown by the largest spokes, was E, whereas the the prevailing wind blows from the W. 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 3% of the time, equivalent to 11 days. Open water swells exceeding >3m (>10ft) only occur 0.2% of the time in a typical year, equivalent to just one day but 3% of the time we expect swell in the range 2-3m (6.5-10ft) 3%, equivalent to (11 days). Taking into account the proportion of these swells that coincided with expected offshore winds, and given the fact that Usami is quite sheltered from open water swells, we think that that clean surf can be found at Usami about 3% of the time and that surf is messed up by onshore wind -1% of the time. This is means that we expect 7 days with waves in a typical year, of which 11 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.