Island Shadowing

Island Shadowing Is the effect of blocking and reducing of a swell when they are heading through neighboring islands. As buoys predict a much larger swell, islands will block and reduce the swell significantly.

As a swell encounters island bottoms the swell starts to slow and change direction or refract. There are Islands all over the ocean. There could be hundreds of overlapping islands and sea mounts spread over a couple thousand miles. As the swell approaches any island it is bending and changing direction towards the shallow areas and it refracts every time it encounters lower depths. As the swell bends and refracts it loses a lot of energy, size and power.

The swell will eventually refract around islands but again it is greatly reduced leaving behind lots of energy, both in size of the waves and the consistency of the sets.

When Island shadowing is fully in effect a good rule-of-thumb is the swell is reduced by at least 50 percent+ of its energy (swell height and wave consistency). However, a good thing is, the swell direction will always range a little here and there, allowing some swell approaching from the sides on the border of the islands allowing sets to peak through.