Numerical diagnosis of tropical cyclogenesis based on a hypothesis of helical self-organization of moist convective atmospheric turbulence

A novel diagnosis for tropical cyclogenesis is presented by examining helical self-organization of moist convective atmospheric turbulence in a rotating, non-homogeneous atmosphere. Our original research approach employed near-cloud-resolving numerical simulations, which allows quantitative diagnosis of cyclogenesis when the primary and secondary circulations in a forming hurricane vortex become linked by deep rotating cumulonimbus cores—Vortical Hot Towers (VHTs). It is shown here how the generated linkage makes the nascent vortex an integral helical system and allows a positive energetic feedback between the circulations that, with adequate moisture fluxes from the underlying sea surface to maintain convective instability, provides a self-sustaining amplification process on the system-scale circulation. The performed investigation suggests that diagnoses using helicity may not only provide an answer to the important question of when will cyclogenesis commence, given a favorable tropical environment, but will help develop a universally accepted definition of tropical cyclogenesis that does not yet exist.