Characteristics of mesoscale convective systems during monsoon extreme rainfall events: case studies from the southwest coast of India

This study investigates and quantifies the characteristics of Mesoscale Convective Systems (MCSs) associated with extreme rainfall events that occurred in 2018, 2019, and 2024, and compares them to heavy rainfall events that took place between 2020 and 2021, with a focus on the southwest coast of India, which has been experiencing devastating torrential rains since 2018, resulting in significant loss of life and property. The MCSs are tracked for these events using high temporal (15-min) and spatial resolution (3 km) Meteosat SEVIRI geostationary satellite observations. The MCS characteristics for the years marked by extreme rain events 2018, 2019, and 2024 stand out as unique, exhibiting an expansive area of approximately 1010 to 1011 m2. The extreme event that occurred on 29 July 2024 was catastrophic, triggering an enormous landslide in Wayanad, a northern district of Kerala, early on 30 July 2024, claiming over 300 lives, with many others still unaccounted for. Compared to 2019, the extreme rainfall event of 2024 is particularly prominent, with a strong clustering of MCS proximal to the coast. The observations indicate that the precipitation associated with 2024 is more severe than it was in 2019. The study highlights that the transition from heavy to extreme heavy rainfall over the southwest coast is facilitated by the aggregation of massive MCS over the southwest coast. The clustering of MCS is a proxy for strong moisture convergence over the southwest coast, which can aid in robust ascending motions and ultimately, extreme rainfall. Through this study, we emphasize the importance of real-time monitoring of MCS over the southwest coast in the current scenario of recurring extreme events over this region.