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Genesis of Pre-Hurricane Felix (2007)The formation of pre Hurricane Felix (2007) in a tropical easterly wave is examined in a two-part study using the Weather Research and Forecasting (WRF) model with a high-resolution nested grid configuration that permits the representation of cloud system processes. The simulation commences during the wave stage of the precursor African easterly-wave disturbance. Here the simulated and observed developments are compared, while in Part II of the study various large-scale analyses, physical parameterizations, and initialization times are explored to document model sensitivities. In this first part the authors focus on the wave/vortex morphology, its interaction with the adjacent intertropical convergence zone complex, and the vorticity balance in the neighborhood of the developing storm. Analysis of the model simulation points to a bottom-up development process within the wave critical layer and supports the three new hypotheses of tropical cyclone formation proposed recently by Dunkerton, Montgomery, and Wang. It is shown also that low-level convergence associated with the ITCZ helps to enhance the wave signal and extend the "wave pouch" from the jet level to the top of the atmospheric boundary layer. The region of a quasi-closed Lagrangian circulation within the wave pouch provides a focal point for diabatic merger of convective vortices and their vortical remnants. The wave pouch serves also to protect the moist air inside from dry air intrusion, providing a favorable environment for sustained deep convection. Consistent with the authors' earlier findings, the tropical storm forms near the center of the wave pouch via system-scale convergence in the lower troposphere and vorticity aggregation. Components of the vorticity balance are shown to be scale dependent, with the immediate effects of cloud processes confined more closely to the storm center than the overturning Eliassen circulation induced by diabatic heating, the influence of which extends to larger radii.
Document ID
20120002760
Acquisition Source
Headquarters
Document Type
Reprint (Version printed in journal)
External Source(s)
Authors
Wang, Zhuo
(Illinois Univ. at Urbana-Champaign Urbana, IL, United States)
Montgomery, M. T.
(Naval Postgraduate School Monterey, CA, United States)
Dunkerton, T. J.
(Naval Postgraduate School Monterey, CA, United States)
Date Acquired
August 25, 2013
Publication Date
June 1, 2010
Publication Information
Publication: America Meteorological Society Journal of the Atmospheric Sciences
Publisher: American Meteorological Society
Volume: 67
Issue: 6
ISSN: 0022-4928
Subject Category
Meteorology And Climatology
Funding Number(s)
CONTRACT_GRANT: NSF ATM-0733380
CONTRACT_GRANT: NSF ATM-0851554
CONTRACT_GRANT: NNG07HU171
CONTRACT_GRANT: NNH04CC63C
CONTRACT_GRANT: N001408WR20129
CONTRACT_GRANT: NSF ATM-0715426
Distribution Limits
Public
Copyright
Other

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