Supplemental Material for: Examining the Roles of the Easterly Wave Critical Layer and Vorticity Accretion During the Tropical Cyclogenesis of Hurricane Sandy

The tropical cyclogenesis model described in Dunkerton et al. (2009), and tested herein for the case of Hurricane Sandy (2012), provides a comprehensive description of the dynamics and thermodynamics that lead to the formation of a tropical cyclone. The model outlines the relevant physical processes and multi-scale interactions and can be summarized by the following three hypotheses (reproduced from Dunkerton et al. 2009). H1. Proto-vortex cyclonic eddies instrumental in TC formation are intimately associated with the parent wave s critical latitude in the lower troposphere. The critical layer and Kelvin cat s eye within, formed as a result of the wave s finite-amplitude interaction with its own critical latitude, contain a region of cyclonic rotation and weak straining/shearing deformation in which synoptic waves and mesoscale vorticity anomalies, moving westward together, amplify and aggregate on a nearly zero relative mean flow. This multi-scale interaction provides a dynamical pathway to bottom-up development of the proto-vortex from below. H2. The critical-layer cat s eye of the parent wave provides a set of quasi-closed material contours inside of which air is repeatedly moistened by convection, protected to some degree from lateral intrusion of dry air and impinging vertical shear, and (thanks to its location near the critical latitude) able to keep pace with the parent wave until the protovortex has strengthened into a self-maintaining entity. H3. The parent wave is maintained and possibly enhanced by diabatically amplified eddies within the wave (proto-vortices on the mesoscale), a process favored in regions of small intrinsic phase speed. See also: ADA612369