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Basic Ocean Terms

Image Credit: Meteorologist Joshua Kelly

When meteorologists are forecasting for ocean-going vessels, there are a few terms that we need to understand. The first term is wavelength. Wavelength is defined as the distance between two crests or between two troughs as seen in the image above.

The example above highlights the crest to crest concept of wavelength. The next term that we use is wave height, and to determine this, we first must look at the wave when it passes our station. When it’s passing the station, we can get a rough visual on how high the wave is. This is the hardest part. However, a good rule of thumb is to imagine oneself inside the wave. How high would it come up on you if you were standing in the wave? Looking in between the two crests, we will find the lower part of the wave. This area is called the trough of the wave.

Now, in addition to that information we can also look at the direction the wave is coming from. This will help us identify where the storm is. Most of the time when we have large wavelengths, this is indicative of a stronger storm system. Once the waves get smaller and have a finer wavelength, we know that the storm is further away from us. When you travel through the doldrums, you will note that waves are very seldom present. This would be called calm seas, and it’s an indicator of very low wind speeds. However, on the other hand, if we have large waves that are close together, we then have strong winds near us creating these larger waves.

There are two types of waves that we need to focus on while at sea. The first is called the wind wave, which is just that, a wave created by the wind that is at our station or vessel. The second type of wave is called a swell wave; these waves have the larger wavelength. These waves are usually created by storms that may be further away from the ship. However, they transport their way towards the ship.

All of these indicators from the ocean can be crucial in preparing a weather forecast while at sea. Here is an example;
If we are traveling west, and we have a huge wave that is pushing us towards the west, we would be able to identify that the storm is behind us to the east. With that being said, we can anticipate that we are moving towards high pressure, so the winds will get lighter and the skies will become partly cloudy with fewer clouds. The waves will get smaller because of the lack of winds. Just by looking at the ocean waves, we are able to generate such a detailed weather forecast daily while at sea.

Basic Ocean Terms


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