Tropical Cyclone Inner-Core Kinetic Energy Evolution

Abstract

Abstract Tropical cyclone (TC) destructive potential is highly dependent on the distribution of the surface wind-field. To gain a better understanding of wind structure evolution, TC 0-200 km wind-fields from aircraft reconnaissance flight-level data are used to calculate the low-level area-integrated kinetic energy (KE). The integrated KE depends on both the maximum winds and wind structure. To isolate the structure evolution, the average relationship between KE and intensity is first determined. Then the deviations of the KE from the mean intensity relationship are calculated. These KE deviations reveal cases of significant structural change, and, for convenience, are referred to as measurements of storm size (storms with greater (less) KE for their given intensity are considered large (small)). It is established that TCs generally either intensify and do not grow, or weaken or maintain intensity and grow. Statistical testing is used to identify conditions that are significantly different for growing versus non-growing storms in each intensification regime. Results suggest two primary types of growth processes: (1) secondary eyewall formation and eyewall replacement cycles, an internally dominated process; and (2) external forcing from the synoptic environment. One of the most significant environmental forcing is the vertical shear. Under light shear, TCs intensify but do not grow. Under moderate shear, they intensify less but grow more, and under very high shear they do not intensify or grow. As a supplement to this study, a new TC classification system based on KE and intensity is presented as a complement to the Saffir-Simpson hurricane scale.