Meridional Flow pattern of October 23, 2003. Note the amplified troughs and ridges in this 500 hPa height pattern.
Meridional flow is a meteorological term meaning that the general flow pattern is north to south along the earth's longitude lines (the opposite of zonal flow). Extratropical cyclones in this environment tend to be stronger and move slower. This pattern is responsible for most instances of extreme weather, as not only are storms stronger in this type of flow regime, but temperatures can reach extremes as well, producing heat waves and cold waves depending on the equator-ward or poleward direction of the flow.
