Formation of Swells, Sets and Waves
What is Swell?
The word Swell can be said to have two meanings.
1. Ground swell: Created by low pressures, wind and storms far out at sea, generating energy across the surface of the ocean from downward air pressure. Thus forming swells which can then travel hundreds, sometimes thousands of miles along the bottom of the sea bed (ground), before they reach their destination and break into waves.
2. Local wind swell: Created again by low pressure systems and winds, although, in this instance a lot closer to shore. Local wind swells are not as desirable as ground swells due to the local wind only whipping up the sea for a short distance (or amount of time) making the eventual breaking waves known as weak or inconsistent compared with a ground swell which can result in consistent, defined, quality waves lasting up to several days.
Large waves created by large low pressure weather systems out to sea.
The larger the depressions out at sea, like hurricanes, the bigger the swell is likely to be and more often than not, generating better quality waves that last for a longer period of time.
How are sets of waves formed?
Like the ripples in a duck pond, the centre of where the storm is formed is where the energy for our waves originate. The bigger the storm, stronger the wind, the bigger the waves, the better and more consistent the sets of waves will be that break on our shores.
As the energy from the centre of the storm propagates outwards into the ocean, the fast energy lines catch up with the slow ones and slowly start to form a set of waves. Depending on the distance travelled by the swell, the various local weather systems that precede the initial low pressure, along with several other elements that all come in to play will dictate how big, consistent or good that particular swell is.
A set of clean defined waves rolls into Fistral beach in Newquay.
There are many other complicated factors that all combine into how a set of waves is formed and cannot easily be explained in one simple answer, without referring to other factors such as “wave periods” or “swell direction”.
*This post is aimed to give a very simple overview of surf science and merely highlights some of the more obvious factors that go into what cause waves to be formed.
Look out for future “Learn to Surf-Theory” blog posts in the coming weeks.
See our Surf Lessons here: www.cornishwave.com/learn-to-surf