Abstract: Based on conventional ground and upper air observation data,radar data,and ERA5reanalysis data,this study analyzes the causes of an extreme precipitation and gale in early winter in Shandong.The results reveal that the eastward movement of a low trough,the southward press of cold air,and the“blocking”situation formed by the low altitude shear line in coordination with the highpressure dam in the northeast and northwest of the ground contribute to the occurrence of extreme precipitation.The water vapor condition in this process is characterized by extreme values,with water vapor flux convergence much stronger than the climate mean state.The moisture flux convergence regions at 925 hPa and 700 hPa correspond well with rain and snow regions,respectively.Convection is triggered by the asymmetric instability of cold front transit conditions,followed by elevated convection forced by upward-ramus circulation in the inversion layer behind the cold front.The strong cold air disturbance slips from the Inner Mongolia Plateau to the North China Plain,then converges with the cold advection and intensifies,generating stronger variable pressure wind and resulting in the conversion of potential energy to kinetic energy and momentum down.Topographic forcing enhances subsidence movement and the formation of frontal secondary circulation in the lower layer of north China.The warm interface of the front region is the convergence of geostrophic deviation,and the cold interface is the divergence of geostrophic deviation.The circulation is characterized by large values of horizontal kinetic energy and geostrophic deviation,and the northerly airflow and descending movement transport the horizontal kinetic energy southward and downward,leading to extreme surface winds.