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ZONAL AND MERIDIONAL FLOW

METEOROLOGIST JEFF HABY

When the upper level winds are parallel or nearly parallel to the lines of latitude the wind pattern is termed zonal. When the winds cross the latitude lines at a sharp angle, the wind pattern is termed meridional. In a meridional pattern the jet stream will have highly amplified troughs and ridges. Low pressure systems tend to move faster (west to east) when associated with a zonal flow. A highly meridional flow can cause atmospheric blocking and spells of much below and much above normal temperatures. A meridional pattern, which its highly curved flow, generates more vorticity than that associated with a zonal flow. Forecasting becomes more challenging when the jet stream has a meridional pattern.