Effect of the Initial Vortex Structure on Intensification of a Numerically Simulated Tropical Cyclone

Abstract

The dependence of intensification rate (IR) of a tropical cyclone (TC) on its initial structure, 14 including the radius of maximum wind (RMW) and the radial decay rate of tangential wind 15 outside the RMW, is examined based on ensemble of simulations using a nonhydrostatic 16 axisymmetric cloud-resolving model. It is shown that the initial spinup period is shorter and the 17 subsequent IR is larger for the storm with the initially smaller RMW or with the initially more 18 rapid radial decay of tangential wind outside the RMW. The results show that the longevity of 19 the initial spinup period is determined by how quickly the inner-core region becomes nearly 20 saturated in the middle and lower troposphere and thus deep convection near the RMW is 21 initiated and organized. Because of the larger volume and weaker Ekman pumping, the 22 inner-core of the initially larger vortex takes longer time to become saturated and thus 23 experiences a longer initial spinup period. The vortex initially with the larger RMW (with the 24 slower radial decay of tangential wind outside the RMW) has lower inertial stability inside the 25 RMW (higher inertial stability outside the RMW) develops more active convection in the 26 outer-core region and weaker boundary-layer inflow in the inner-core region and thus 27 experiences lower IR during the primary intensification stage. vortices -1 day