Abstract:  Based on the NCEP reanalysis data, the mesoscale weather systems of a short-time rainstorm process occurred on May 27, 2008 at Laohekou of Hubei province were analyzed. The results show the movement of mesoscale weather systems of a short time rainstorm such as dry line, cold trough at 500 hPa, convergence zone of rear of cold shear line, wet area at middle and low levels and convergence line of ground wind field and so on are closely related with the occurrence and development of heavy rain. Dry air invades the wet area from north to south and from upper to lower, which is of typical features of rainstorm caused by dry invasion in Hubei province. Dry invasion makes dry-cold air and warm-wet air rising jointly, and it causes the positive vorticity at the convergence area of rear of cold shear line developing upward along the front area of θse, which enhances convective ascending motion in coordination with ground wind field convergence. Cold trough at 500 hPa and dry intrusion result in convective instability, and the convergence of cold-warm advection, dry-wet advection at the rear of cold shear line forms the unstable region at the horizontal direction. The unstable region is disturbed by dew point front, so convective weather is triggered. The sustainability of deep-wet area at middle and low levels and water vapor convergence provide the water vapor source for this process.

Key words: Mesoscale rainstorm, Dry intrusion, Convergence zone of rear of cold shear line, Cold trough, Convergence line of ground wind field, Wet zone