The contribution of M. T. Montgomery was prepared as part of his official duties as a United States Federal Government employee.
Do tropical cyclones intensify by WISHE?
Article first published online: 9 OCT 2009
Copyright © 2009 Royal Meteorological Society
Quarterly Journal of the Royal Meteorological Society
Volume 135, Issue 644, pages 1697–1714, October 2009 Part A
How to Cite
Montgomery, M. T., Sang, N. V., Smith, R. K. and Persing, J. (2009), Do tropical cyclones intensify by WISHE?. Q.J.R. Meteorol. Soc., 135: 1697–1714. doi: 10.1002/qj.459
- Issue published online: 26 OCT 2009
- Article first published online: 9 OCT 2009
- Manuscript Accepted: 11 MAY 2009
- Manuscript Revised: 7 MAY 2009
- Manuscript Received: 20 NOV 2008
- local buoyancy;
- vortical hot tower
In this paper we seek and obtain a basic understanding of tropical cyclone intensification in three dimensions when precipitation and evaporative-cooling (warm rain) processes are included. Intensification with warm rain physics included is found to be dominated by highly localized deep convective structures possessing strong cyclonic vorticity in their cores—dubbed ‘Vortical Hot Towers’ (VHTs). Unlike previous studies, the findings herein suggest an intensification pathway that is distinct from the ‘evaporation–wind’ feedback mechanism known as wind-induced surface heat exchange (WISHE), which requires a positive feedback between the azimuthal-mean boundary-layer equivalent potential temperature and the azimuthal-mean surface wind speed underneath the eyewall of the storm. Intensification from a finite-amplitude initial vortex is shown to not require this evaporation–wind feedback process. Indeed, when the surface wind speed in the sea-to-air vapour fluxes is capped at a nominal (trade-wind) value, the vortex still intensifies by the same pathway identified in the main experiments via the generation of locally buoyant VHTs and the near-surface convergence that the VHTs induce within the boundary layer.
The present findings and interpretations challenge the prevailing view that tropical cyclones are premier examples of vortical systems arising from WISHE. Given the potential significance on our understanding of the dynamics of hurricanes, and given the limitations of the present modelling framework, further tests of these predictions are advocated. Copyright © 2009 Royal Meteorological Society