Key Factors Modulating the Threat of the Arabian Sea's Tropical Cyclones to the Gulf Countries

Tropical cyclones (TC) are one of the biggest natural hazards with significant threat to life and property due to storm surge, flooding and extreme winds. Combined, these hazards substantially increase the potential for loss of life and damage especially in populated landfall-locations such as the countries on the Arabian Gulf and Sea of Oman. Hence, it is important to identify the factors that modulate the trajectory of TC in order to better predict their lifetime and dynamics. Since 1900, only two TCs moved into the Sea of Oman and made landfall on the southeastern coast of the Arabian Peninsula (AP): TC Shaheen in 2021 and Gonu in 2007. In this study, the mechanisms behind the exceptional trajectories of these two TCs are investigated. Both TCs developed during the active phase of the Madden-Julian Oscillation, and benefited from above-average sea surface temperatures (SSTs), ocean heat content and reduced vertical wind shear. Their paths over the Indian Ocean were controlled by large-scale forcings, whereas regional-scale processes, such as the local SST gradients and the Arabian Heat Low (AHL) defined their trajectories near landfall location over the AP. An exceptionally deep AHL was present during these events. The AHL is found to interact two-way with TCs: its associated circulation drags the TCs inland while the TCs, through the advection of cooler marine-air inland, cause the collapse of the AHL. It is recommended to account for the AHL as fluctuations in its position and strength can determine where future TCs make landfall.