Rules Governing Winds in Relation to Pressure
Systems
Northern Hemisphere Based Upon Actual Observations
A. Surface Pressure Systems Only
- Air flows counterclockwise and inward with respect to LOW PRESSURE AREAS and clockwise and outward with respect to HIGH PRESSURE AREAS.
- Air flows fastest the GREATER THE PRESSURE DIFFERENCE across an area (the closer the isobars).
B. Pressure Systems At All Levels Except
the Surface
- Air flows parallel to the isobars (or height contours), counterclockwise around LOW PRESSURE and clockwise around HIGH PRESSURE areas.
- Air flows fastest the GREATER THE PRESSURE (or height) DIFFERENCE across an area (the closer the isobars or height contours).