Revisiting the Relationship Between Tropical Cyclone Rapid Intensification and the Distribution of Inner-Core Precipitation

Abstract

The relationship between tropical cyclone (TC) rapid intensification (RI) and the distribution of inner-core precipitation preceding RI is reexamined using satellite-based precipitation measurements and best-track data. TCs experiencing RI (RITCs) are classified into weakly, moderately and highly asymmetric categories according to the 25th and 75th percentiles of an objective asymmetry index. Composite results indicate that weakly-to-moderately asymmetric RITCs experience precipitation axisymmetrization before RI, resulting from increased coverage of both light-to-moderate (0.5–10 mm hr−1) and intense rainfall (>10 mm hr−1) upshear. Contrarily, the rainfall asymmetry strengthens significantly before RI in highly asymmetric RITCs due to an outbreak of intense convection downshear left, demonstrating climatologically that RI is not necessarily preceded by rainfall axisymmetrization. It is hypothesized that the different rainfall evolution characteristics may be explained by the balanced intensification theory, and the azimuthal-mean precipitation rate normalized by TC intensity could be a predictor for RI regardless of the rainfall asymmetry.