The torrential rain had happened in the southwest of Hebei province on August 3-5 in 1996.This torrential rain was resulted from the interaction of the landed typhoon 9608 low,subtropical high and weak cold air from northeast.Because of cold air diffused toward the typhoon low,the wet baroclinic front was generated.Then,three mesoscale convective cloud cluster were generated,developed at the north of typhoon low.