Diagnostic analysis of a torrential rain process in north Sichuan Basin

Based on the routine observation the diagnosis of a torrential rain process in north Sichuan Basin during 18-19 July 2005 is made and the circulation feature is analyzed.This heavy rain process attributes to the3 influence of upper and lower shear lines.The surface cold fronts and the southerly low-level jet streams are blocked by the southwest Pacific subtropical high together.The location of the heavy rain with its strength and duration can be analyzed by using the θse,the divergence of vapor flux and the divergence of the modified wet Q-vector.