Coriolis Effect

Coriolis force [effect] deflects the winds aloft so that they rotate clockwise around a high pressure system and counterclockwise around a low pressure system. The winds aloft move parallel to the isobars.

Surface friction causes the winds near the surface to be slower and, therefore, less affected by Coriolis force. Surface friction causes the surface winds to flow across the isobars at an angle rather than parallel to the isobars.