Revisiting the tropical cyclone genesis potential index for the Bay of Bengal post-monsoon season.

Bay of Bengal (BoB) is known to host intense tropical cyclones (TCs). The accurate determination of BoB cyclogenesis remains a challenge for the scientific community. Detailed assessment of existing genesis potential indices (GPI) reveals their inability to replicate the variability of TC frequency in the BoB. This study developed a GPI (nGPI), which displays better/equal skill in estimating TC genesis despite using less number of variables compared to the existing GPIs. The nGPI has significantly higher skill in capturing the interannual variability of TC frequency as compared to the most previously developed GPI during the 1993–2022 post-monsoon season. Our analysis further reveals that the dominant contribution to the interannual variability in the GPI comes from the mid-level relative humidity (~44%) and the low-level relative vorticity (~39%). The contribution of tropical cyclone heat potential is ~17%. The nGPI exhibits higher values when the number of observed TCs is higher and vice versa for a lower number of TCs. Further, our analysis reveals that the dynamic parameters have a limited role in governing the interannual variability of TC frequency in the BoB during the post-monsoon season. This study thus advocates the use of nGPI for future TC simulation/projection studies using CMIP models, where the availability of high-resolution parameters at multiple pressure levels is often limited. Furthermore, this newly developed GPI can serve as a reliable proxy for projecting TC frequency under various climate scenarios over the BoB during the post-monsoon season. [ABSTRACT FROM AUTHOR]