The weakened low of Typhoon YAGI and RUMBIA crossed Shandong Province on 14 and 19 August 2018. The surrounding circulation produced multiple tornadoes and brought about serious economic losses. Based on the data of Doppler weather radar, conventional observations, weather conditions, and disaster investigation, the environmental physical variations and structural characteristics of intensity of tornado storms are analyzed, and the signatures of microscale cyclonic vortices that induced and did not induce tornadoes are compared. The results show that the northeast quadrant of two weakened low-pressure circulations is the key area for the occurrence of tornadoes. The low-level high humidity, strong low-level vertical wind shear, and large storm relative helicity are key physical quantities. Tornadoes are accompanied by microscale cyclonic vortices with ΔV larger than 20.0 m·s-1, which occur mainly below 2.0 km, but not all such low-level microscale cyclonic vortices can induce tornadoes. With ΔV larger than 20.0 m·s-1 as the threshold, the hit rate of tornado recognition is high, the accuracy of tornado recognition is 31.8%, the false alarm rate is 67.4%, and the missing alarm rate is 6.7%. About 35.7% of the tornadoes are unable to be identified in advance, and half of the tornadoes have almost no early warning time.