Characteristic differences between two contrasting tropical squalls

Abstract

Abstract: Climatic changes and the recent surge in weather extremities are alarming concerns for society today. Tropical squall events with extremely heavy rainfall and lightning are among the very severe ones among such activities. Usually, squalls have a leading convective edge followed by a stratiform trail

however, the reverse is also observed in rare cases. This work presented a thorough study on a conventional and an unconventional squall with nearly similar severities from a tropical location, Kolkata. The study reports notably high wind gusts and lightning activities during both events, with the latter one showing higher values. The CAPE increase and OLR drops were significant in both the cases. Breakage of storm front were noticed in the first squall, which possibly resulted in higher CAPE surrounding the study location even though the localised value was slightly larger during the second event. The unconventional squall having a shorter life cycle showed weaker vertical wind shear. The cloud system during the second squall structure showed dominance of smaller cloud particles and lower cloud top pressure than the first event, whereas the cloud mask fraction and cloud water path were large in this case. The rain microphysics has been studied for the two said events and a greater number of drops has been observed in the reflectivity through region than in the stratiform phase for the squall with trailing convective line, unlike the one with conventional structure. The rain microphysical properties showed clearly distinguishable behaviour during the three phases of the squall passage for both the events. Exceptionally high a values in empirical relation between Z and R were noticed in both the cases. The study reports higher path attenuation during the first event. The study can be useful in improving the understanding of the efficiency of different atmospheric and precipitation microphysical features in the predictability of a mesoscale system. Research highlights: (1)The current work has presented a thorough analysis of two tropical squalls with different organisational modes.(2)The variation in associated weather variables has been studied for the two events.(3)A thorough study of precipitation microphysics has been carried out for the two squalls.(4)The conventional factors used for prediction of mesoscale systems were analysed in detail for these cases to understand the efficiency of these elements in prediction of an unconventional convective system like a squall with a leading stratiform edge studied here. © 2023, Indian Academy of Sciences.