Analysis on a Non-typical Torrential Rain Event Associated with Cold Air in Autumn

Diagnostic analysis on a non-typical cold air associated torrential rain in Southern Guangdong is performed by using conventional observational data,automatic weather station data and the NCEP reanalysis data(1×1 deg) as well as the Doppler radar data.Results show that(1) obvious mesoscale characteristics can be identified in this case;(2) vertical upward motion began in advance of the occurrence of the heavy rain,while the low level moisture convergence agreed well in time with the intensity of precipitation;(3) accumulation of the instability energy beforehand is necessary,the invasion of the cold front is the trigger mechanism,and the distribution of the convective available potential energy(CAPE) in a degree indicates the probable torrential rainfall areas;(4) the intensity and the development of radial velocity convergence of radar can give us some indications of the evolution of the convective echoes.