A unified view of tropical cyclogenesis and intensification

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Authors
Kilroy, Gerard
Smith, Roger K.
Montgomery, Michael T.
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Date of Issue
2016
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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 (Vmax = 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.
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Article
Description
Quarterly Journal of the Royal Meteorological Society
The article of record as published may be found at http://dx.doi.org/10.1002/qj.2934
Department
Meteorology
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Naval Postgraduate School
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Funded by Naval Postgraduate School
Office of Naval Research Global
NOAA HFIP
National Aeronautics and Space Administration
Deutsche Forschungsgemeinschaft
National Science Foundation
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This publication is a work of the U.S. Government as defined in Title 17, United States Code, Section 101. Copyright protection is not available for this work in the United States.
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