WX MODEL 13: Meridional Flow


Meridional flow is a jet stream flow (i.e. 300 mb) in which there is an amplified trough-ridge pattern. The flow changes latitude abruptly as the flow through the jet stream is assessed. The opposite would be a zonal flow in which the wind moves pretty much straight along a line of latitude. Meridional flow will produce variations in weather as a location experiences warmer weather in a ridge followed by cooler weather in a trough. This can produce several days of warm and sunny weather followed by several days of cold weather with precipitation chances.

The model image below shows a Meridional pattern at 300 mb. There is a tall skinny ridge along and off the west coast of the United States. The jet stream flow is directed around this ridge which causes the flow to abruptly change in latitude. Once over the United States, the flow goes through a wide and large trough.