Last week’s blog focused on the genesis of ocean waves. This weeks I will attempt to breakdown the often lengthy journey open ocean waves take on before reaching the coastline. We know that from low-pressure storm activity, strong winds can create waves that can exceed 50-feet in height. Waves of these immense heights are common within the fetch and just outside the area of storm activity but decay rapidly during the initial distance traveled. kind of like how a brand-new car driven off the car lot instantly loses value, waves generally lose between 80 – 90 per cent of their energy in the first 100 miles traveled away from the area of storm activity. So, an initial wave height of 30-feet will be reduced to 6-feet, soon after traveling away from the area of propagation.
Once waves travel out of the fetch, or area where the wind is the generating force, they are no longer wind waves and in-turn identified as free waves, or what we understand as ground swell.
For me, the most intriguing characteristic of waves is wave speed. As waves travel away from the storm’s influence they begin to organize into groups of waves with similar period and wave length called wave trains or wave groups.