What does trough anterior and posterior mean?

The so-called trough before and after the ridge means that the east of a certain area is a high-pressure ridge and the west is a low-pressure trough. The area is in the transition zone between the high-pressure ridge and the low-pressure trough. Therefore, we call this area Behind the anterior ridge of the trough. In the wind field, southwesterly winds often blow from the front and back of the trough, and the air is relatively humid. If there is no cold air trigger, the weather will not be bad.

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Personally, I think that if the ground is behind the trough front ridge and the upper altitude is controlled by the subtropical high, the TC will also move along the subridge and land somewhere~~~~