Three non-supercell tornadic storms in Shandong Province were analyzed based on doppler radar data from Jinan and Yantai in combination with environmental parameters and weather events. The results showed that: The environment situations were conducive for the thunderstorms occurring. The greater humidity in the lower level, the significant 0~1 km vertical wind shear and the favorable topographic played an important role in the occurrence of three non-supercell tornadoes. Three tornadoes formed during the rapidly developing stages of thunderstorms, the storm top and the height of the maximum reflectivity markedly increased by more than 2 km within 6 min, although the maximum reflectivity had no significant changing sometimes. The strong updrafts, quickly building up within storms, and the favorable topographic were the main incentives for the occurring of tornadoes. The strong updraft lifted the horizontally rotating wind shear into a vertical position. This mechanism and favorable topographic effect intensified the small-scale circulation within the updraft, called a small-scale vortex. If this area of circulation intensified enough, the circulation reaches the ground as a tornado.
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