Cause Analysis on the Heavy Rainstorm in Luzhou in the Early Summer of 2014

Using a variety of observational data to analyze the cause of heavy rain storm of Luzhou, which occurred on 2nd~4th June, 2014. The results show that:(1) compared with the past heavy rainstorms, the circulation situation of the heavy rain storm is atypical and it displays that 500 hPa influencing weather systems are weak, the position of subtropical high is anomaly southward, the range of low-level wind field convergence is large and it's hard to determine the heavy rain zone. (2) The two precipitation periods of the heavy rain occur with development and re-development of a MCS of middle α-scale. At the first stage, two MCSs of middle β-scale in Nanchong and Luzhou respectively merged into one MCS of middle α-scale and developed strongly to arouse heavy rainfall of Luzhou-Chongqin, then gradually moved to the northwest of Guizhou and weakened. At the second stage, the MCS of middle α-scale developed intensely again in Guizhou, Luzhou appeared heavy rain again by its edge influence. (3) Seeing from the configuration of different height weather systems, the most notable feature is that there is a strong cold advection, the cold advection of the first phase came from the northwest flow of the rear of north cyclone and formed the interaction of cold and warm in Luzhou. At the second stage, cold advection mainly came from the mid-latitudes eastward low trough, the cold advection had influenced Luzhou and formed the interaction of cold and warm in northwest of Guizhou. Therefore, cold advection plays an important role in the heavy rainstorm.