It’s very seldom that a sailor is able to just point his boat at the place he wants to sail to and arrive there by sailing in a straight line! This is partly due to the design of sailboats which preclude them from sailing directly in the direction that the wind is coming from. Destinations are inevitably somewhere close to the direction that the wind is coming from!
So sailors, being resourceful people, took a look at the way our planet works and devised a series of routes that although being longer, had the benefit of the wind from behind the boat for at least most of the time. These routes are called Trade Wind Routes and are the routes that sail-powered ships took to move people and cargo all over the planet before the advent of steam-powered vessels. Very briefly, the way the planet works is that there are very cold bits at the poles and a very warm bit in the middle. As we know, warm air rises, in this case around the equator, and cold air moves towards the equator to fill in the vacuum that would otherwise develop if it didn’t. If the earth did not spin, this would be the end of the lesson, with the wind in the Southern Hemisphere moving from south to north and vice versa in the Northern Hemisphere. But the earth does spin and creates something called the ‘Coriolis effect’ resulting in the winds sheering off towards the west under the effect of the spinning. It still sounds nice and symmetrical and predictable at this point, but each ocean is slightly different in temperature and size and has different currents running around it. This has the effect of creating high-pressure systems that more or less dominate large parts of the hemispheres that they are in and dictate the wind direction and strength. In the area that I have sailed from, the South Atlantic, there is a high-pressure system that sits around the middle of the ocean between Africa and South America and is known as the South Atlantic high, or the St Helena high. Because of the Coriolis effect, the wind rotates anti-clockwise around this high.
On the north side of the equator, we have another high-pressure system known as the Azores High. The wind around this system, because of Coriolis, revolves clockwise. In between the two high-pressure systems, in general terms, is a lot of hot air moving slowly from east to west, or going straight up and leaving vast calm patches on the water. So in order to sail from the southern, to the northern hemisphere, a sailor will position his boat on the eastern edge of the South Atlantic High and let the anti-clockwise winds push him north and west as far as the equator. Where he will stop. Hopefully not for too long. Once over the equator, he will position his boat on the bottom west edge of the Azores High and let the South East, then Southerly and then ultimately Westerly winds that are rotating clockwise around the high-pressure system push his boat in a north and easterly direction, assuming that is where he wants to be pushed! Otherwise, he’ll peel off towards the Caribbean or North America before getting pushed that far!
I’m at that stage where I am experiencing easterly winds along the bottom of the Azores High and I’m allowing them to push me North West and North so that I can meet up with the clockwise winds from the West that will push me towards the Azores and Europe when I get north enough.
That should be within the next three days hopefully and then it’s a five day sail to Horta in the Azores for a pit stop and then a last push towards the UK.