AUTOMATIC INCORPORATION OF NUMERICAL SHORT-RANGE PROGNOSES IN 5-DAY CIRCULATION FORECASTS

Abstract

One of the basic aids in the preparation of extended forecasts is a 5-day mean mid-tropospheric chart centered on the day of the forecast, with associated instantaneous height tendencies, the unknown data being computed by autocorrelation techniques. Substitution of values from the barotropic 24-hour and 48-hour numerical prognoses for these unknowns objectively incorporated recent gains in short-period prognoses. Comparison of the statistically and physically computed mean charts and their tendencies suggests superiority of the latter over North America and the Atlantic, but not over the Pacific where errors in the barotropic prognoses, which are probably due to improper boundary assumptions and omitted physical processes, play an important role. Dynamic considerations can be applied to the new mean chart to suggest subsequent changes which may not be indicated kinematically.