Extended Abstract (96K)4C.6
A closer look at vortical hot towers in a tropical cyclogenesis environment
Andrea B. Saunders, Colorado State University, Fort Collins, Colorado
Over the past several decades there has been considerable interest in determining what mechanisms are responsible for the transformation of a midlevel mesoscale convective vortex (MCV) into a tropical cyclone. It is a generally accepted fact that convection plays an important role in tropical cyclone intensification, yet convective-scale processes are absent from many current tropical cyclogenesis theories. Given the numerous observational studies indicating that deep convective blow-ups are a precursor to tropical storm formation, we believe one must also consider the role of the emergent convective structures in the spin-up process.
Using the non-hydrostatic CSU RAMS model, we have run cloud-resolving simulations of tropical cyclogenesis from a single initial midlevel MCV embedded within a moistened tropical environment. The time period leading up to development of a surface-concentrated vortex is before the onset of WISHE, and is dominated by the presence of vortical hot towers (VHTs). Our study focuses on characterizing VHTs and their role in the development of a tropical storm vortex. We describe a mechanism whereby deep convection can generate strong collocated vertical vorticity anomalies by tilting and stretching of MCV-related vorticity, and explain how this vorticity can increase hot tower lifetimes within a typical MCV environment. Our findings suggest that convective-scale dynamical processes play a crucial in the transition from a midlevel MCV to a tropical cyclone and motivate the need for higher-resolution simulations and a field campaign to further investigate these ideas.
Session 4C, tropical cyclogenesis IV
Monday, 3 May 2004, 3:45 PM-5:15 PM, Napoleon II Room
Previous paper
Recorded presentation