What do you mean, before the groove and after the ridge?

The so-called pre-trough ridge and post-trough ridge mean that an area is high-pressure ridge in the east and low-pressure trough in the west, and this area is in the transition zone between high-pressure ridge and low-pressure trough, so we call this area behind the pre-trough ridge. In terms of wind field, southwest wind often blows behind the front ridge of the trough, and the air is humid. If there is no cold air trigger, the weather will not be very bad. Fa]/nNWHr_

Personally, if the ground is behind the trough front ridge and the height is controlled by the subtropical high, TC will also move along the subtropical ridge line and land somewhere.