Convective bursts during the rapid intensification of Hurricane Dennis (2005): Precipitation morphology and vortex evolution

It is well-known that diabatic heating plays a crucial role in governing tropical cyclone (TC) genesis, intensity change, and structure. The role this heating plays is dependent on several factors, including its magnitude, longevity, horizontal and vertical distribution, and the characteristics of the vortex. The morphology of the precipitation, e.g., magnitude and horizontal and vertical distribution of diabatic heating and vertical motion, mode of organization (i.e., convective vs. stratiform), determines the impact of this precipitation on the intensity, structure, and rainfall of the vortex. Observational, theoretical, and numerical modeling studies have shown the importance of deep convection in tropical cyclone genesis and intensification. Multiple theories have been advanced to explain how these bursts of precipitation, often occurring episodically, facilitate genesis (e.g., vortical hot towers in the convective cores, midlevel mesoscale convective vortices in the stratiform regions), and intensification (primarily through bursts of deep convection and their associated stratiform precipitation).

While the importance of these episodic bursts of precipitation has been documented, what has not been thoroughly documented is the morphology of the precipitation associated with these episodes, how this morphology may vary as a function of the lifecycle stage of the TC and location within the developing storm, the importance of any such variations in TC intensity change, and whether numerical models can reproduce these variations if they exist. This research addresses these issues, focusing on the intensification phase by investigating whether precipitation morphology, as measured by the statistical properties of various microphysical fields, varies as a function of TC lifecycle stage and location within the storm. A combination of a high-resolution simulation and airborne observations during the intensifying stage of Hurricane Dennis (2005) are analyzed here. This work may shed some light on the importance of convective and stratiform processes in an intensifying tropical cyclone.