Ridges and Trough aloft - Highs and Lows at the Surface 500 mb Chart Notice that ridges aloft are associated with Highs at the surface Troughs aloft are associated with Lows at the surface. |
Surface Pressure
This association of ridges/troughs with Highs/Lows occurs most of the time, BUT NOT ALWAYS The surface lows are referred to as (midlatitude) cyclones The surface highs are referred to as anticyclones |