SEMI-OBJECTIVE FORECASTING OF ATMOSPHERIC STAGNATION IN THE WESTERN UNITED STATES

Abstract

Forecasts of air pollution potential by semi-objective means are demonstrated and shown to be useful in delineating stagnation areas associated with the quasi-stationary anticyclone and ridge aloft over the western United States. Past stagnation episodes i.e., prolonged periods of very low wind speed, variable wind direction, and pronounced atmospheric stability near the surface, were used in the preliminary tests of the forecast procedure; results obtained were sufficiently encouraging so that the forecast scheme was applied on a daily basis for the 4-mo. period beginning October 1962 and ending January 31, 1963. The effectiveness of the daily forecasts of high air pollution potential is shown by the air quality data collected during forecast periods of atmospheric stagnation.