A Numerical Study of Convective‐Scale Structures in the Outer Cores of Sheared Tropical Cyclones: 1. Updraft Traits in Different Vertical Wind Shear Magnitudes

Abstract

AbstractThis study investigates the outer‐core convective‐scale updraft features of numerically simulated tropical cyclones under vertical wind shear of different magnitudes. Updrafts in the outer core were weighted in favor of downshear formation, and the increase in the shear value led to more short‐lived updrafts. The tops of detected updrafts tended to cluster at either 4‐ to 6‐km or 12‐ to 14‐km height. Downshear‐left updrafts mostly moved radially inward, and updrafts on the left side of the shear vector moved more rapidly azimuthally. Longer‐lived updrafts gained greater vertical mass fluxes during their life cycles, with those in strongly sheared tropical cyclones having larger vertical mass fluxes for the same updraft life span. The height of stronger vertical velocity in convective bursts decreased as shear increased, whereas larger vertical velocity within nonconvective‐burst cells held between 3 and 4 km. The values of several environmental parameters (such as the supercell composite parameter and the energy‐helicity index) associated with updrafts in the downshear‐left quadrant were larger than those in the downshear‐right quadrant for the weakly sheared tropical cyclone, whereas they became much larger in the downshear‐right quadrant for highly sheared vortices. There were no relationships between the parameters and updraft mean mass fluxes, so the use of these parameters for predicting the likelihood of updraft strength in tropical cyclones requires caution.