Using the data of ERA5 reanalysis as well as a new generation of radar mosaic data, a sudden rainstorm in Northeast Sichuan Basin was fully analyzed, including its influencing systems and dynamic impact factors.The analysis indicates that the predominate influencing systems of this process are the middle-latitude trough in 500 hPa moving to east, the Western Pacific subtropical high which extends to west, the southwest low-level jet（SWLJ） in the lower troposphere and the shear line of low layer.The large-scale SWLJ and the meso-micro scale low-level jet in mountainous terrain built a dynamical coupling of the positive vorticity column and strong divergence column in low-level.The strong upward vertical movement, result from the convergence ascending of low-level jet exit region and the local topographic forcing, which is the trigger condition in the rainstorm.The potential instability stratification established by the low-level jet is the thermal condition of this rainstorm.The main reason for the increase of precipitation in the second stage is that cold air gradually intrudes into the upper layer from the lower layer.The topography in Northeast Sichuan Basin is the enhancement factor in the process of rainstorm.It influences the vertical ascending motion through the uplift effects.The windward slope of Qin-Ba mountainous is relatively strong on first stage and the eastern leeward slope of the Qinghai-Tibetan Plateau is relatively strong on the second stage.What’s more, the mountains terrain in Northeast Sichuan Basin make the mesoscale convection systems (MCSs) stagnant in Sichuan Basin and develop fully through the blocking effect.
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