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

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