Waves or sea waves are a critical aspect of sailing and passage planning. What are waves and how are they created? The sea or water acts as a medium to transfer energy of the wind across the surface of the water. The amount of surface wind blowing over the seas surface and for how long and the distance the waves are able to travel dictates the size, length, amplitude, period and frequency of each individual wave.
Passage planning and weather forecasts are both important elements in a safe and enjoyable sailing experience. Get it wrong and it can be a stressful and dangerous sailing experience. With the worse case scenario of the complete loss of a sailing boat. But that’s fairly rare. But you only have to look at a nautical charts around the coast of British waters to see the number of wrecked and sunken vessels to keep that in mind.
On occasion oceans can produce massive freak or rogue waves which at one time were thought to be rare occurrences but now proven to be not the case.
Surface winds generate energy and sustain high winds generate and transfer large amounts of energy across oceans and sea surface and produce waves. So passage planning and timing is extremely critical for small sailing boats. However, as previously mentioned most boats sink or are wrecked closed to land. Large open seas even with big waves small suitable ocean sailing boats are quite safe and they pop up and down like a small corks on the surface of the biggest waves. What are extremely dangerous are the freak or rogue waves that are breaking and in the process produce tons of cascading water off their wave fronts.
These freak or rogue waves are usually caused by oceans currents or tidel forces or a change in topography of the coast or headland or a continental shelf. A rising underwater sea mount or rapid change of wind direction causing a confused sea which has the possibility to create a freak wave. Wind against a fast tidal flow. Something has to produce this large rogue wave on the surface of the water a disturbance of some sortto produce these large freak waves.
So waves form through the blowing of the wind over the surface of the water the long and harder the winds blow the bigger the waves.
The topography of the sea bottom does make quite a big difference. Waves have the following features; wave length from top of one crest to next crest, the wave frequency, the wave amplitude or wave height, all factors have to be taken into account whilst sailing. The secret is to try and take adventure of natures forces such as when leaving harbour when the tidal forces will push you along, or sailing more down wind than into the wind and waves. Not leaving a harbour just after a storm force winds. Its important when sailing to make the experience pleasurable. Nothing worse than a long beat into the high winds and big waves. Passage planning is such an important element of safe and pleasurable sailing.
I remember clearly one moon lit night off Cabo Ortegal north west Spain I was sailing down wind and the amazing feeling of sailing along a magic moving carpet. But this sense of movement from waves is an illusionary experience. Deep Ocean water of 4000mtrs creates long wave lengths with sustain winds. But shallow depths of 200 to 20 Metres can cause short wave lengths with higher wave frequencies. Therefore it’s generally safer to be in deep water.
These are waves have large amplitudes and long wave lengths but with much lower frequencies. One of the reasons why the Bay of Biscay can be a dangerous stretch of water is due to winds being blown from the west causing a boats to be on a lee shore and the steep rise of the continental shelf which rises from 4000m to 200m. This helps pile up the water and cause confused sea with shorter wave length and higher wave frequencies. Rogue waves do exist and not as rare as first thought. Ships have been lost to them mostly due to them breaking their backs. but in reality its still a rare situation, it’s more about being in the wrong place at the wrong time. You’re much more likely to be killed in car accident then ever in sailing boat through rogue wave. Things must be kept in perspective whilst out on the sea.
https://youtu.be/CVsdXKO9xlkhttps://youtu.be/2ylOpbW1H-I