H marks the center of a high pressure area.
The barometric pressure is higher there than at surrounding places. The force of this pressure causes air to move out and away from the high pressure center. Because of the rotation of the Earth, the flow turns to the right in the northern hemisphere. We wind up with air appearing to spiral out and away from the high pressure center. In order for the pressure to stay high, more air must be drawn into the high pressure area at somehigher altitude.