Environmental and Boundary Layer Characteristics Associated With Intensity Change of Tropical Cyclones Under High Fullness

Abstract Tropical cyclone (TC) fullness, which measures the ratio of the annular width of the vortex skirt region to the total width of the outer wind field, is an important metric for characterizing TC wind structure and intensity change. High fullness is typically beneficial for intensification, but there are situations where high‐fullness TCs do not intensify. This study explores the structural characteristics and environmental conditions of weakening TCs under high fullness. Identifying these situations can be helpful for improved prediction of TC intensity change. This study analyzes 5,218 GPS dropsondes from 36 TCs to compare structural and environmental conditions of intensifying (IN) and weakening (WE) TCs under high fullness. For the environmental conditions, TCs tend to weaken with strong southerly vertical wind shear, dry air, and less ocean heat content, suggesting that more adverse conditions are required to offset the favorable effects of high fullness. In terms of structural characteristics, WE TCs have a warmer, moister boundary layer but weaker surface fluxes than IN TCs. Additionally, WE TCs exhibit stronger inward advection of absolute angular momentum within the friction layer. Above the frictional inflow layer, WE TCs display weak outflow, whereas IN TCs exhibit weak inflow. The implications of these differences in surface enthalpy fluxes and radial flow above the friction layer are discussed within the context of recent hypotheses regarding boundary layer ventilation and TC intensification.