How is a wave formed? Understanding Swell and Surf Forecasts
How is a wave formed? The surf report, the swell and surf forecasts are a result of scientific studies and weather prediction models. In order to know what type of surf we will get in the next days, it's important to learn how waves are created.
Waves are mainly a product of the wind. The best waves for surfing are the result of the interaction of winds on the surface of the ocean, far away from the coast. Wind is the first step in the formation of surfable waves.
Local shore winds can also produce waves, but they can also destroy the quality of the breaking waves. Onshore winds are typically known for creating choppy and bumpy waves because their effect is added to the direction of the wave.
In a way, offshore winds are a sort of a counterbalance. Swell comes from miles away and the ground wind works as a "pause-hold" effect on the wave face, allowing longer unbreakable waves.
Low Pressure Systems | Good Waves for Surfing
In theory, low pressure systems are responsible for creating good and strong waves. In deep low pressure systems, wind speed is greater and more waves are generated by the power of the gusts.
The friction created by these winds helps to form energy waves that will travel thousands of miles until hitting final obstacles, which means, coastal areas where we live.
If winds created in low pressure systems keep blowing the surface of the ocean for a long time, swells will be bigger because energy is accumulated in all waves produced.
Also, if low pressure winds affect a very large area of the ocean, all waves produced by the swell will have even more energy and power, resulting in even bigger waves.
From Ocean Waves to Surfing Waves | Sea Floor and Swell Obstacles
We've already analyzed the "birth" of swell and correspondent waves, but there's a large distance to be traveled by those waves. Original oceanic waves may have to run a long journey until they reach continental beaches.
Along the way, until they are ridden by surfers, these waves will have to challenge other variables. The height of a wave when it is created is not the height of the waves that is ridden by a surfer.
Waves make their way through the ocean and are affected by the differences in the ocean floor. When large volumes of water move and pass by higher sea floors, the overall energy of the swell is changed.
For example, offshore continental shelves are friction resistances to moving waves and when these waves reach coastal areas in shallow water conditions, swell has already lost intensity, energy and power.
When waves travel without obstacles, in deep water regions, they tend to reach a beachfront with huge force. Bathymetry studies the underwater depth of ocean floors and its changes over time.
In the bathymetric map, it’s easy to understand the highest and lowest depths on the entire planet Earth. Sea floor topography is very important to avoid disasters and accidents with ships and line cruisers.
Also, the study of sea floor can deliver precious forecasting information for your local surf spot. When waves reach shallow waters they tend to slow down. Despite that, wavelength is shortened and the crest of waves grows, meaning that the wave height rises.
Sand Banks | Increasing the Wave Crest
Sand banks, for instance, are always changing in beach breaks. That’s why the quality of the waves is better or worse through time. The sand bumps in the ocean floor allow the formation of clear and localized wave peaks, from where surfers can take off on a ride.
A new sand bank normally means a new wave peak because swell hits the sand obstacle and pumps the wave crest allowing surfable waves. Other swell obstacles are jetties, sunken boats or simply natural and artificial reefs.
Waves start wind winds and are influenced by sea floor, rainfall, tides, coastal backwash currents and local winds and sea bottoms. All these weather and geological variables result in waves for surfers, kitesurfers, windsurfers and bodyboarders.
Learn what is wind and how wind is formed.
Discover the importance of swell period in surfing, and the difference between ground swells and wind swells.
Now, check the wave height forecast for your local spot.
Surf Forecasting: Wind and Wave Truths
1. Long-period waves tend to be larger and stronger
2. Short-period waves are smaller and less energetic
3. Wave period is the time between successive crests
4. Wave frequency is the number of waves passing a point in a specific time
5. Large waves move quickly
6. Small waves move slowly
7. Low pressure systems create a powerful swell
8. Low pressure systems are associated with rainy weather and cloudy skies
9. High pressure systems are associated with warm weather and clear skies
10. Deep water coastlines deliver bigger waves
11. Tsunamis cannot be surfed