The role of oceanic parameters in genesis potential indices for enhancing tropical cyclogenesis forecasting in the Bay of Bengal

This study presents an advanced approach for forecasting tropical cyclone genesis, a critical component of disaster preparedness and mitigation for coastal regions prone to extreme weather events. Unlike traditional Genesis Potential Indices (GPIs), which rely solely on atmospheric parameters, we propose a novel GPI framework that integrates both atmospheric (relative vorticity, relative humidity, vertical wind shear, thermal instability) and oceanic variables (Upper Ocean Heat Content [UOHC], Sea Surface Height [SSH]) to enhance predictive skill over the Bay of Bengal (BoB). Building on earlier works, we introduce improved indices GPIS and GPIS1 by incorporating oceanic parameters and evaluate their performance against the existing atmospheric-only index GPIK for four post-monsoon cyclonic events ( Kyant, Bulbul, Bruvi , and Mandous ) during 2016-2022. During Cyclone Bulbul the highest correlations (r = 0.94) were recorded between GPIS and GPIS1, and between GPIK and GPIS, with the lowest RMSE (2.44) between GPIK and GPIS. For Cyclone Mandous , GPIK and GPIS1 showed the strongest correlation (r = 0.96) and lowest RMSE (1.79), while GPIK-GPIS maintained a good correlation (r = 0.88) with an RMSE of 4.68. GPIS1 consistently outperformed the other indices, particularly when paired with GPIK, and detected developing low-pressure systems 3-4 days in advance significantly earlier than the 1-day lead time of the India Meteorological Department’s operational GPI. These results highlight the novelty and value of integrating atmospheric and oceanic parameters in GPIs, and underscore the benefits of multi-index analysis for capturing storm-specific variability and improving early identification of cyclogenesis in the BoB during the post-monsoon season.