What causes high pressure systems to always rotate clockwise; low pressure systems to rotate counterclockwise?
I’ll give this one a try. First of all, your quesiton only applies in the Northern Hemisphere. Southern Hemisphere weather is reversed. It is the rotation of the earth which causes this rotation to happen. High pressure regions PUSH air outward from their center. Let’s look at a sample “piece” of air moving due north from a region of hgh pressure. As it moves north, the earth underneath it rotates to the east. So if you were standing on the earth watching that piece of air moving north, it would look like the air is also moving west since you are moving east. This turns into a clockwise flow. Conversely, air flows INTO a low pressure region. As a “piece” of air comes from the north headed south into a low pressure region, the earth rotates underneath it which means the piece of air is now farther west than when it began, which looks like a counter-clockwise flow.
