The Implication of Outflow Structure for the Rapid Intensification of Tropical Cyclones under Vertical Wind Shear

The implication of outflow structure for tropical cyclone (TC) rapid intensification (RI) is investigated via a climatological study using the best track, reanalysis, and infrared brightness temperature data during 1980–2019. Composite analyses are performed in a shear-relative framework for the RI events under different strengths of environmental shear. Results show that for the RI events under moderate (4.5–11 m s −1 ) or strong (>11 m s −1 ) environmental shear the RI onset follows a significant increase of upper-level outflow upshear of the storm, which is intimately linked with the increasing active convection upshear. The intensified outflow blocks the upper-level environmental flow and thus decreases the local shear, building an environment favorable for RI. In contrast, the RI under weak environmental shear (