The Summarization of the severe convective weather on November 9 in the middle and lower reaches of Yangtse River

A fargoing heavy rain occurred on November 9 in 2009 in the middle and lower reaches of Yangtse River. There are also the gale, hail and short-duration heavy rain exist in Hunan, Hubei, Jiangxi, Zhejiang, Fujian etc. Analysis indicate that the severe convective weather occurred when the low pressure trough move eastward, then form cyclone and move into the sea at last. This disaster mainly caused by the mesoscale squall line and the mesoscale convective system. From moisture point we can see that the middle and lower reaches of Yangtse River have high humidity. Further the south west low level jet provide the enough vapour for this region. The intrusion of cold air at the mid-level and the calefacient surface provide the high instability for this region. The cold air encounter the warm air at the low level. The strong frontogenesis, the low pressure trough at the surface and the shear line at the low level caused the severe convective weather at last.