Dynamical and thermodynamical aspects of an extreme rainfall event over Telangana

The present study investigates the background meteorology of an extreme rainfall event over Telangana (Deccan Plateau; mean elevation ~ 500 m) during July 26–27, 2023 using observations, reanalysis data and HYSPLIT back trajectories. More than 50 stations across 11 districts of Telangana experienced extremely heavy rainfall (> 20.4 cm) on this day, with the highest rainfall of 62.04 cm recorded over Chityal. Radiosonde observations from Ramgundam showed the presence of water vapour saturation in the altitude region of 925 − 400 hPa. The precipitable water vapour (PWV) obtained from the radiosonde was greater than 75 mm and the K index was greater than 40. The INSAT-3D Thermal Infrared Brightness Temperature (TIR-BT) indicated the presence of deep convection and a cyclonic circulation pattern over Telangana with a TIR-BT minimum around July 27, 00 UTC. Doppler Weather Radar (DWR) observations revealed the presence of a mesoscale cyclonic circulation with a maximum reflectivity of 40–45 dBz over the region at the time of high intensity rainfall. ERA-5 showed a positive temperature anomaly, higher relative humidity and relative vorticity in the free troposphere and a strong updraft reaching the tropopause on this day. The spatial distribution of PWV showed an elongated, high moisture plume extending from northeast Maharashtra to northern Andhra Pradesh. The cyclonic circulation present over Telangana on this day was only present in the altitude region above 2 km. Back trajectory analysis showed that moisture laden air below 2 km which led to the accumulation of water vapour over this region originated from the Arabian Sea.