By using conventional data,as well as AWS( automatic weather stations) and NCEP1° ×1° and FY2E T_(BB)data,the causes of regional rainstorm in Shandong from July 31 to August 1 2012 are analyzed. The results indicate:( 1) The low-level shear line and cold front were a major weather system of the rainstorm. The high-temperature and high humidity and strong southeast flow provided temperature and humidity conditions in the rainstorm area.( 2) Low-level frontogenesis forced ageostrophic vertical circulation int...