Let’s move on now to swell “Refraction” - surfers like myself enjoy this event and it is important in Swell Forecasting 101. I have had my share of closing-out sets
In oceanography, wave refraction is the bending of a wave as it propagates over different depths. ... The event takes place because shallow water depths actually slow down the wave train, while the part of the swell moving over deep waters continues at the same speed.
In other words, it is the process by which the direction of a traveling wave is changed due to the interaction with ocean's bottom’s topography.
I have not experienced this, but I have talked with some South Florida surfers who have experienced a very unique refraction process in which swells actually "bounce" off of the Little Bahama Bank and reflect on an angle back into Florida
We are putting together the components of Swell Forecasting 101 as mentioned in the pages above
We should be able to understand better some of my reports (oldmanwaves.com) for the San Onofre State Park which broadcasts from Cotton to Trails
As we see above we have Swell Periods and Swell Direction
Add to this our last entry of swell ‘Refraction”
Our next discussion will be on Swell Diffraction
We are putting together more components of Swell Forecasting 101 as mentioned in the pages above. In our above branch we have gone over swell ‘Refraction”
Our next discussion will be on Swell Diffraction - Some surf reports mention the term swell wrapping, that mostly means swell diffraction
Diffraction occurs when a wave encounters an obstruction in its path and will change direction, or wrap around it. In ocean waves, we see this occur when a diffraction will involve a change in a wave’s direction.
How does this actually Occur?
A swell encountering an Island is potential for both refraction and diffraction. In short, the Island acts as a barrier and we see diffraction occur as the waves wrap around it. The bending of the waves then intensifies as they encounter shallower water around the Island, thus refraction occurs.
Off the coast of California there are a few islands - Has anyone gone to the beach to surf only to find smaller waves than reported? Timing of the above mentioned wrap could be the answer?
A very important component of Swell Forecasting 101 is the 'Wind"
Simply put, when strong winds (a fetch) begin to gust and blow on a stretch of calm water far out at sea, ripples are formed on the surface. These ripples turn into waves that make their way towards the coast. A swell is a collection of these waves produced by the fetch. Strong winds blowing hundreds of miles off the coast can make surfers travel to the beach looking to surf.
Onshore wind: means blowing from the sea towards the land and produce short lumpy and bumpy mixed surf. This type of wind reduces the steepness of the wave by toppling the wave wall earlier making a shorter ride. This wind destabilizing the wave and resulting in bumpy sporadic surf breaking throughout the duration of the ride
Offshore wind: This type of wind is one that blows from the coast to the sea. This wind produces longer walls and longer rides because the wind direction will delay when the waves will break.
The speed of the wind, even offshore wind can affect your takeoff - What is you cutoff point for speed?
Ex. Offshore winds of 15 MPH or more for me, makes it difficult to take off without moving closer to shore and I'm a strong paddler. I'm usually going for the outside sets