Key factors behind super cyclone Gonu (1–7 June 2007) over the Arabian Sea

Abstract

Super Cyclone Gonu (1–7 June 2007) was the first recorded Category 5 tropical cyclone in the Arabian Sea and one of only five Super Cyclonic Storms reported by the India Meteorological Department over the past 35 years. Forming shortly after the onset of the Indian Summer Monsoon, Gonu’s rapid intensification during a typically unfavorable period for cyclogenesis represents a remarkable deviation from climatological norms. This study examines the atmospheric and oceanic factors that enabled its development using ERA5 reanalysis, NOAA OISST, and IMD Best Track data. Analyses show that anomalously high sea surface temperatures, elevated mid- to upper-tropospheric humidity, and low-to-moderate vertical wind shear created a highly favorable thermodynamic environment. A southward intrusion of midlatitude westerlies disrupted the Tropical Easterly Jet, enhancing upper-level divergence and supporting vigorous deep convection. Vertically integrated moisture transport revealed strong southwesterly inflow into the cyclone core, with concurrent diversion of moisture from the Indian subcontinent, temporarily delaying monsoon progression. Rainfall analyses from GPCP and IMD datasets indicate intense and asymmetric precipitation, with significant orographic enhancement over coastal regions. Organized low-level vorticity and persistent moisture convergence sustained Gonu’s structural integrity until landfall. These findings highlight the interplay of ocean–atmosphere interactions, large-scale circulation, jet stream variability, and precipitation dynamics in early-season cyclogenesis and emphasize the importance of integrated forecasting for extreme tropical cyclones in a changing climate.