The effect of remote typhoon"Conson"and NW flow on a rainstorm event in Jiangxi

A composite analysis is performed for the rainfall in Jiangxi province during 14-15 July 2010 based on GFS reanalysis data, merged precipitation products, conventional observation data and satellite data. Intensive discussions are made about the effects of the remote typhoon and NW flow. The results show as follows. (1) The storm rainfall is caused by the interactions of multi-scale weather systems, including the vortexes, subtropical high, remote tropical depressions, west trough, meso-scale system with the situation of NW flow. (2) The interactions between remote typhoon and NW flow are beneficial to the stability and development of the vortexes. It also makes the upper level divergence synchronously strengthened with low level convergence. (3) Abundant water vapor and energy are transported from low-latitude areas to storm rainfall regions by the converging southern air flows, which are favorable for the accumulation of water vapor and unstable energy. Cold air from upper level and warm moisture air are mixed up over the rainstorm area, which simulates the baroclinic frontal zone. (4) Horizontal and vertical gradient of baroclinic frontal zones increase with the effect of NW flow and remote typhoon, which also strengthen the vertical wind shear. All these factors are favorable for the development of cyclonic vorticity and frontogenesis. Strong upward flow comes across the frontal zone, which simulates the vapor convergence and convection, and leads to the rainstorm. (5) In prediction, intensity of external forcing systems should be estimated, such as subtropical high, cold trough on 500 hPa, typhoon, etc. For one thing, forecasters should contrast the intensity of upper and lower systems to find out the leading one. On the other hand, change of lower disturbance environment may also be noticed.