Precipitation Structure Upshear and Its Role in Tropical Cyclone Intensification

The relationship between precipitation structure and tropical cyclone (TC) intensification has received considerable attention in the literature.  Recent aircraft, satellite, and modeling-based studies have identified different modes of precipitation, e.g., deep convection vs. shallow convection and stratiform precipitation, as having differing importance in indicating TC intensification is either about to start or has already begun.  In general, intensification has been associated with a higher distribution of deep convection inside the local radius of maximum wind and a greater azimuthal coverage of precipitation of all types.

This study will present results from recent and ongoing case study and composite analyses of airborne Doppler radar data of the structure of precipitation on the upshear side of TCs and its relationship with TC intensification.   Deep convection is more prevalent upshear in intensifying TCs, and it has stronger updrafts, with peaks at a higher altitude and higher echo tops, than non-intensifying TCs.  Shallow to moderate convection and stratiform precipitation on the upshear side, possibly associated with moistening of the midlevels, are seen prior to and during intensification.  These results suggest a complex interplay between precipitation structure and TC intensification, with processes that provide a more favorable local environment for the maintenance of convection upshear being an important player.