Groundswell vs. Windswell

Ever been reading the surf report and seen the swell being referred to as a windswell or a groundswell and not really known what that meant?  Me too.  I looked it up.

Think of local, surface action for windswells.  Windswells are swells created by regional winds on the relative surface of the ocean.  (Think globally though, so regional is within a few hundred miles of your break.) Typically the periods are short for windswells, less than 10 seconds between peaks.  Energy from windswell waves tends to dissapate quickly (the lower levels of the ocean absorb the swell from the surface), so they can’t travel too far.  (Again, globally speaking.)  But the good news for surfers is that windswell waves usually come to shore in consistent sets.

Groundswells are more like successful windswells that beat the odds to travel the world. Groundswells often start as windswells, but rather than dissipate, they build and spread.  They can travel much farther and last much longer than their wind bretheren.  More and more energy transfers deeper into the ocean which translate into longer wave periods (for better travel).  Due to the depths the groundswell can reach, often the energy of the wave will be reflected off the ground and amplifies the wave as it moves into shallower water.

So, what to take away from this?  Generally if a groundswell is noted, you might expect more energy from the waves. If it’s windswell, chances are the sets will be more consistant.  But like all bits from a forecast/report (tide, swell direction,…) it’s only a piece of a much larger pie that plays into what the waves are going to be like.