Doppler radar analysis of a tornadic miniature supercell during the Landfall of Typhoon Mujigae (2015) in South China

Abstract

n 4 October 2015, a miniature supercell embedded in an outer rainband of Typhoon Mujigae produced a major tornado in Guangdong Province of China, leading to 4 deaths and up to 80 injuries. This study documents the structure and evolution of the tornadic miniature supercell using coastal Doppler radars, a sounding, videos and damage survey. This tornado is rated at least EF3 on the enhanced Fujita scale, and is by far the strongest typhoon rainband tornado yet documented in China and possesses double funnels near its peak intensity.Radar analysis indicates that this tornadic miniature supercell exhibited characteristics similar to those found in US landfalling hurricanes, including hook echo, low-level inflow notches, echo top below 10 km, small and shallow mesocyclone, and long lifespan (~3 h). The environmental conditions consisted of moderate CAPE, low lifted condensation level, small surface dewpoint depression, large veering low-level vertical wind shear, and large cell-relative helicity that are favorable for producing miniature supercells. The mesocyclone, with its maximum intensity at ~2 km above ground level, formed an hour before tornadogenesis. A tornado vortex signature (TVS) was identified between 1 and 3 km AGL, when the parent mesocyclone reached its peak radar-indicated intensity of 30 m s-1. The TVS was located between the updraft and forward-flank downdraft, near the center of the mesocyclone. Dual-Doppler wind analysis reveals that tilting of low-level vorticity into the vertical direction and subsequent stretching by a strong updraft were the main contributors to the mesocyclone intensification.