Exploring genesis potential indices

That the large-scale environment has a role in determining tropical cyclone genesis has been understood since the earliest analyses of the association between cyclones and the general circulation in the tropics. Gray (1968, 1979) summarized the state of science and demonstrated the potential for assessing genesis potential utilizing such environmental parameters as ocean thermal content, midlevel moisture, an unstable atmosphere, low-level vorticity, and vertical wind shear through a deep atmospheric layer. Building on this earlier work, a number of cyclone genesis indices have been developed and are being utilized to assess potential hurricane changes over climate time-scales. A recent index developed for North Atlantic tropical cyclones combines an index of available energy for cyclone development with the negative influences of strong vertical shear and has demonstrated skill in assessing annual cyclone frequency variations (Bruyère et al., 2012). Following on from this study, here we examine a number of global cyclone regions with the goal of establishing similar predictors of annual cyclone counts.