关键词: 非超级单体龙卷, 卫星云图特征, 雷达回波特征, 龙卷涡旋特征（TVS）

Abstract: Seven tornadoes attacked in Shandong on 14 August 2018 under the effect of spiral rain belt around the typhoon ‘YAGI’, and the non-supercell tornado affected Jianglou Town of Huimin County was up to disaster-inducing standard with F2 level. Based on conventional observation data, satellite cloud images, radiosonde data and Doppler radar data, the non-supercell characteristics during the strong tornado process were analyzed. The results show that the tornado occurred in spiral rain belt around the typhoon ‘YAGI’, and it was about 160 km from the center of the typhoon with 35° direction, in which the gradient of humidity and TBB were large. The large-scale circulation backgroud, low-level jet stream, lower lift-up condensation level (LCL) and larger vertical wind shear in low level were conducive to the occurrence of tornado. The small-scale vortex at the initial stage appeared near surface layer first, then it developed upward and strengthened, while the weakening and disappearance was from upper level to low level, and the rapid declining and jump rising process of strong central height of the maximum reflectivity factor was well corresponded to the emergence and disappearance of ground tornado. The small-scale vortex occurred on 0.5° elevation of radar radial speed 7 minutes before the tornado occurred, which indicated that the tornado was grounding or imminent. The apparent rise of small-scale vortex top height can be used as an indicator of the rapid enhancement of tornado.

Key words: non-supercell tornado, satellite cloud image characteristics, radar echo characteristics, tornado vortex signature (TVS)