Well, what you have observed is actually an artefact of the Earth's rotation. This is combined with water and solar energy to create the weather patterns that we experience.
Think of the main weather driver as a series of giant convection systems that operate in belts around the Earth (six in total - three in the northern and three in the southern hemispheres). The inner most belts extending into the north and south of the tropics have the greatest influence, as they receive the highest solar energy.
As you know, hot air rises. This is what happens constantly around the tropics, whilst drawing air in from north and south of the tropics at surface level to replace the air that has risen. The air can only go so far up before it runs out of room in the atmosphere and has to deflect to the north and south of the tropic zone, eventually cooling and falling back to the surface of the Earth in the lower temperate zone to continue the convection cycle.
How does this create the prevailing winds I hear you ask?
Remember that the Earth is a sphere that rotates on an axis. Air rises at the equator at relatively the same speed as the Earth's surface. So if you were on the equator, the air would generally seem fairly still because it is mostly swirling and moving upwards towards the sky (unless you were in a tropical storm of course).
When this air deflects north and south after rising, it maintains a lot of the surface speed generated at the equator, making it relatively faster than the Earth’s surface the further north or south you go. Remember, the circumference of the Earth at the equator is larger than at any other longitude, so it has further to travel each revolution and thus is why it is faster relative to the rest of the Earth’s surface speed.
So, the further north or south the air from the tropics travels, the more it seemingly accelerates towards the East because the surface is moving slower than where the air was generated.
I hope this makes sense, because it is hard to explain without being able to draw diagrams. You may want to look up topics like “convection winds” and “coriolis force” to get a better understanding of why there is a previling westerly in the world's temperate zones.
Some pilots will use these winds to their advantage. For example, winter in Australia brings the very fast jetstream westerly winds further north. Airlines will pick up on these winds on PER
-NZ flights (PER
can be over an hour quicker than MEL
during these winds).