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They Will Prevail

October 8, 2013

by Cash

When we get to the Caribbean, we will be sailing to many different islands.  While we sail, we will have to take into account the many different habits of the wind and water, including trade winds, onshore and offshore breezes, and currents.

Prevailing winds are winds that blow in a particular direction most of the time.  Globally, there are large areas in which the direction of the wind blows in a consistent pattern, thus giving them the name prevailing winds.  The prevailing winds in the tropics are called trade winds.  Trade winds blow toward the equator, and are slightly deflected west by the spin of the Earth.  The trade winds in the Caribbean blow mostly towards the west and southwest.  So when we sail east to a different island, it will be hard, because sailing into the wind is the most difficult point of sail.

Onshore and offshore breezes are formed near coasts, especially in sunny places.  An onshore breeze develops during the day.  The sun warms the land causing the air above it to heat up and rise.  Cool air from the ocean is sucked in to replace it, forming the breeze coming onshore.  During the night, the land cools down, but the water stays warm.  Because the ocean is warmer, the opposite of an onshore breeze happens:  warm air rises over the ocean, and air from the land blows offshore to replace it.  We as sailors need to be aware of this because when entering a port, an onshore breeze will blow us toward the port, instead of an offshore breeze blowing us away.  The best time for arriving is in the day, and the best time for leaving is in the evening.

Currents are created when winds blows the water in a specific direction.  Because of the large prevailing winds, the currents are also quite large.  For example, the Gulf Stream runs up the east coast of the U.S., blows over to Europe, down the coast of Africa, and back to America.  When sailing, we'll try to sail on currents that are going with us and avoid the ones that are against us.

We should be aware of all of these things when sailing, but most, like the offshore and onshore breezes, are not crucial.  For example, sailing into port against the wind isn't terrible, it just slows us down a bit.  Still, they are good to know, and will help us sail fast and efficiently to get to the next exciting place.

Aunt Lisa said...

This is cool information, a lot of which I didn't know before. You explained it very clearly. Maybe some other time you can explain how you sail INTO the wind. Also, how do you know where the currents are, to use them to help you along?

Cassius Close said...

Hi Aunt Lisa,
That's a good suggestion. I'll do that some day.
The currents I was talking about are very big ones, like the Gulf Stream, that are always going that same direction. Also, when sailing near land, if the water is going from high tide to low tide, the water will be flowing out from the land, and that will be a current.
Thanks for reading. It's nice to know someone has interest.

Gwendolyn said...

Wow, I never thought of sailing worldwide like that. It's interesting to hear sailing from a more technical viewpoint.