Downhill thunderstorms frequently occur in Beijing during the rainy seasons, leading to substantial precipitation. The prediction of downhill thunderstorm remains elusive, partly attributed to insufficient observational studies that unveil the thermodynamic and dynamic structures along the vertical direction. Here we propose a novel objective method to identify both enhanced and dissipated downhill thunderstorms and detect their evolution. The radar wind profiler (RWP) mesonet in Beijing is used to derive areal divergence and vertical velocity, which are used to characterize the pre-storm environment downstream to the thunderstorms at the foothill. A case study of enhanced downhill thunderstorm on 28 September 2018 is carried out for comparison with a dissipated downhill thunderstorm on 23 June 2018, supporting the notion that a deep convergence layer detected by the RWP mesonet, combined with the enhanced southerly flow, favors the intensification of thunderstorms. Statistical analysis based on radar reflectivity from April to September 2018–2021 have shown that a total of 63 thunderstorm events tend to be enhanced when entering the plain, accounting for about 66% of the total number of downhill thunderstorm events. A critical region for intensified thunderstorms lies on the downslope side of the mountains west to Beijing. The prevailing westerlies, along with divergence in the middle of troposphere exert a critical influence on the enhancement of convection, while low-level divergence may lead to the dissipation. The findings underscore the significant role of the fine scale profiling of the accurate dynamic quantities derived from the RWP mesonet in elucidating the evolution of downhill storm.

downhill thunderstorms,radar wind profiler,low-level convergence