Meridional flow

In meteorology, a meridional flow is a general air flow pattern from north to south, or from south to north, along the Earth's longitude lines (perpendicular to a 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.