Effect of Subjectively Enhancing the Initial Vorticity Field in a Short-Range Numerical Forecast

Abstract

A method of introducing subsynoptic-scale initial data into a six-level primitive equation model is presented. Vorticity perturbations on the scale of subsynoptic disturbances are added to the initial winds; the amplitudes and slopes of the perturbations are subjectively determined from physical, climatological and observational considerations. Balanced winds, heights and temperatures are then derived from the enhanced vorticity fields. Two 12 h forecasts are made from two different initial analyses. The first