Excitation of Deep Convection to the North of Tropical Storm Bebinca (2006)

Abstract

 Tropical storm Bebinca (2006) was characterized by an abrupt termination due to the generation of an explosive convection to the north of its center. No convective clouds were observed near its center, nor did typical cloud patterns with spiral bands and eyewalls appear in the storm. Reanalysis data (ERA-Interim) was used in this study, and a set of sensitivity experiments conducted with a numerical model (NICAM) to examine the cause of the explosive convection.
 The analyses of the reanalysis data elucidated mechanisms for excitation of deep convection, including a high convective available potential energy environment due to moisture convergence at lower levels, potential vorticity generation by a diabatic Rossby vortex mechanism, and dynamical forcing formation of upward motion induced by upper levels.
 Moreover, two sensitivity experiments were conducted by modifying the vortex structure of Bebinca. The results suggested that Bebinca’s unusual characteristic, the weak low-level pressure gradient near the center was fundamental for excitation of the explosive convection in the northern area.