Analysis of a low-precipitation supercell tornado event in dry mountainous environment

An analysis of two EF1 weak tornadoes occurred in Weichang and Longhua including pre-storm environmental conditions and fine structures is made based on the radars in different bands and wind profile radars. The results show that the tornado occurred under the northwest airflow behind the 500hPa cold vortex, and the parent tornado was triggered by the dry line and the ground convergence line.The supercell tornadoes occurred in an pre-storm environmental field with strong convective available potential energy (CAPE) and 0-6km vertical wind shear while water vapor at low level and 0-1km vertical wind shear significantly increased. The afternoon hot thunderstorm activity improved low-level moisture condition. The echo intensity of supercell tornado storms was weak in which Weichang tornado was less than 40dBZ,areal extents were small and the precipitation near the tornado was less than 2mm.The rotating updraft corresponding to the mesocyclone and hook echo head was separated from the precipitation echo.The two tornado storms exhibited the low-precipitation(LP) supercell characteristics. In this paper, the pre-storm environment and structural evolution of two LP supercell storms in China was recorded for the first time. Moderate mesocyclone at low level and tornadic vortex features（TVS） were identified, indicating the X-band radar could capture the LP supercell tornado. The appearance of the TVS had a good temporal correspondence with the occurrence of Weichang tornado, and the Longhua tornado feature was detected 8min before, indicating that the warning time of the LP supercell tornado was short.