A unified view of tropical cyclogenesis and intensification. (23rd December 2016)

• Record Type: Journal Article
• Authors: Kilroy, Gerard; Smith, Roger K.; Montgomery, Michael T.
• Is Part Of: Quarterly journal of the Royal Meteorological Society. Volume 143:Number 702(2017)
• Page Start: 450
• Page End: 462
• Publication Date: 2016-12-23
• Subjects: tropical cyclone -- hurricane -- typhoon -- spin‐up -- cyclogenesis -- intensification; Meteorology -- Periodicals; 551.5
• DOI: 10.1002/qj.2934
• Languages: English
• ISSNs: 0035-9009

Abstract

Abstract : Idealized high‐resolution numerical simulations of tropical cyclogenesis are presented in a model that represents deep convection by a warm rain process only. Starting with an initially weak, cloud‐free, axisymmetric warm‐cored vortex (maximum wind speed 5 m s −1 at a radius of 100 km), rapid vortex intensification begins after a gestation period on the order of 2 days. From a three‐dimensional perspective, the genesis process is similar to that in the rotating convection paradigm for vortex intensification starting with a much stronger initial vortex ( V max = 15 m s −1 ). The patterns of deep convection and convectively amplified cyclonic relative vorticity are far from axisymmetric during the genesis period. Moreover, the organization of the cyclonic relative vorticity into a monopole structure occurs at relatively low wind speeds, before the maximum local wind speed has increased appreciably. Barotropic processes are shown to play an important role in helping to consolidate a single‐signed vorticity monopole within a few hours near the intensification begin time. The rotating convection paradigm appears adequate to explain the basic genesis process within the weak initial vortex, providing strong support for a hypothesis of Montgomery and Smith that the genesis process is not fundamentally different from that of vortex intensification. In particular, genesis does not require a 'trigger' and does not depend on the prior existence of a mid‐level vortex.