Analysis on A Rare Squall Line Weather from Northeast

Based on weather radar,automatic weather station and conventional observation data,the squall line from northeast occurred in the night of 21 June 2005 in Binzhou City was analyzed.The analysis showed the characteristics of the meteorological elements.The system which plays a major role was in the upper troposphere.Transversal trough,shear line,high-altitude cold air,low-altitude warm air,and severe warming on the ground surface were conducive to the promotion of convective instability.They were the causes of producing the squall line. The squall line clouds on satellite images showed dense and oval.They indicated that convection was strong and squall line may be generated. In the radar echo images the squall line showed herringbone or bow,bull's-eye structure and the main front was associated with thin ribbon weak echo which was the sign of the emergence of gale.The wind divergence observed by automatic weather station was related with down-burst, and counter-clockwise changes of the wind direction in vertical wind profile products.