Development and applications of a new Genesis Potential Index

We developed an empirical genesis potential index for tropical cyclones. Our approach largely follows the earlier work of Emanuel and Nolan (and originally, that of Gray), but with a few incremental changes. First, we derived the index using a straightforward, entirely objective Poisson regression method, allowing the derivation of the index to be reproduced by others. Second, we used slightly different thermodynamic predictors: relative sea surface temperature instead of potential intensity, and column relative humidity from satellite microwave retrievals instead of midlevel relative humidity from reanalyses. We first derived the index from the historical climatology on a global basis. We then examined some of the sensitivities and limitations of the approach by deriving the index from data restricted to limited regions of the globe and then testing it on other regions. Finally, we tested the index in the GFDL high-resolution global model HIRAM, both for simulations of the present and future climate change scenarios.