Analysis of a sustained rainstorm event happened in Jiangxi on June 2013

Dynamic diagnosis and mesoscale analysis to a sustained rainstorm event happened in Jiangxi from June 26 to 29,2013 was performed using data from conventional observations,satellite images,the intensive observations from automatic weather station and NCEP reanalysis.The results indicate that this sustained rainstorm event is caused by the interaction among the West Pacific subtropical high,monsoon surge,cold air and shortwave trough from Qinghai-Tibet Plateau.The increase in strength and thickness of vertical movement due to strengthened vapor convergence in the lower troposphere,convergence in the low-level and divergence in the upper level is favorable to the strengthening of the rainstorm.In addition,another favorable factor is the simultaneous strengthening of the ascending branch airflow over intersection of cold and warm air masses and the sinking branch airflow over north side of the intersection.Diurnal variation of southwesterly jet in lower troposphere is closely related to the strengthening of heavy rainfall beginning by midnight.The genesis,development and merging of a series of meso-γ-scale or meso-β-scale convective systems lead to the continuous rainstorm or extra heavy rainstorm in the northern Jiangxi.Strong mesoscale rain clusters tend to move towards the ground convergence line and the large convective instability zone.