The Analyses of Convective Parameters and Their Potential Predictability in a Severe Thunderstorm Rain

The observational data and NCEP data are used to analyze the heavy rain on 45 July 2003. It is found that 1) the large scale systems are very favorable for the occurrence of heavy rain in the Huaihe River. From 29 June 2003 the subtropical high maintained in South China, the warm, moisture air and cold, dry air coming from the trough met in the Huaihe River areas, which was favorable for the maintenance of Meiyu front and the occurrence of the heavy rain. 2) The southwesterly to the south of convergence line transports a great deal of moisture to the convective region. 3) Accompanying with the ascending motion, the strong convergence, positive vorticity in the middle and lower troposphere and the strong divergence, negative vorticity in the upper troposphere contribute greatly to the occurrence and maintenance of the heavy rain. 4) The distribution and variation of the convective parameter, such as Convective Avialable Potential Energy (CAPE), Convective Inhibition (CIN), Lifting Index (LI), K index, indicate successfully the local physical characteristic, which are favorable for the occurrence of heavy rain. The CAPE assembles obviously 23 h earlier than beginning of rain and decreases quickly after its occurrence.