Unraveling the contrasting features of rainfall microphysics for the tropical cyclone Tauktae (2021) and a severe thunderstorm event as observed over the orographic region of Western Ghat

Abstract

Abstract The contrasting feature of precipitation microphysics for the severe weather events over the orographic region of Western Ghat (WG) has been highlighted in this paper. By analyzing the features of precipitation associated with a cyclone and a thunderstorm over Mahabaleshwar – which is regarded as one of the severe rainfall station of Western Ghat orographic region, it has been found that the raindrops of diameter 2.2 mm and above dominates the precipitation associated with thunderstorm than with respect to cyclone. Though the towering thunderstorm surrounding the eyewalls of cyclone produces rainfall of higher intensity during the cyclonic period, but the strong updraft generated during the thunderstorm rainfall event forces the smaller raindrops aloft thereby allowing the larger raindrops to precipitate locally which ultimately results for severe rainfall of very high intensity for shorter duration during those events. It has been observed that the pre-cyclonic effect over orography is characterized by the increase in midlevel relative humidity (700–900 hPa), relative vorticity and cloud ice water content while in case of evolution of thunderstorm, the atmosphere gives strong signal with respect to strong vertical velocity, sudden increase of CAPE and rapid decrease of Lifting Index (LI). In this study, the impact of orographic upliftment, cyclonic circulation and the stronger updraft generated during the thunderstorm period has been critically diagnosed, differentiated and portrayed with respect to the variation of rainfall microphysics for these severe weather events over the elevated terrain.