Rules Governing Winds in Relation to Pressure Systems

Northern Hemisphere Based Upon Actual Observations

A.      Surface Pressure Systems Only

  1. Air flows counterclockwise and inward with respect to LOW PRESSURE AREAS and clockwise and outward with respect to HIGH PRESSURE AREAS.
     
  2. Air flows fastest the GREATER THE PRESSURE DIFFERENCE across an area (the closer the isobars).

 

B.      Pressure Systems At All Levels Except the Surface

                          

  1. Air flows parallel to the isobars (or height contours), counterclockwise around LOW PRESSURE  and clockwise around HIGH PRESSURE areas.

  2. Air flows fastest the GREATER THE PRESSURE (or height) DIFFERENCE across an area (the closer the isobars or height contours).