Type of Document	Dissertation
Author	Evans, Allen Clark
Author's Email Address	ace1636@fsu.edu
URN	etd-08102009-004539
Title	The Thermodynamic Evolution of Recurving Tropical Cyclone Bonnie (1998)
Degree	Doctor of Philosophy
Department	Meteorology, Department of
Advisory Committee	Advisor Name Title Robert Hart Committee Chair Paul Reasor Committee Member Paul Ruscher Committee Member T. N. Krishnamurti Committee Member James Elsner University Representative
Keywords	Extratropical Transition Extratropical Cyclones Cold Fronts Numerical Modeling Thermodynamics Tropical Storm Hurricanes Tropical Cyclone
Date of Defense	2009-07-28
Availability	unrestricted
Abstract One of the defining characteristics of the extratropical transition of tropical cyclones is the transition of the warm core thermal structure associated with the tropical cyclone into an initially cold core thermal structure associated with the extratropical cyclone. Despite this being a defining characteristic of the extratropical transition process, the literature expresses no consensus agreement upon or a quantification and physical description of the factors that explicitly cause this transition to occur. Understanding this evolution is important in order to better forecast and describe the evolution of physical features within the cyclone such as its four-dimensional wind field structure and to begin to quantify the contributors to the poleward transport of heat energy associated with the transitioning cyclone and its impacts upon hemisphere weather patterns and model predictability. This work employs a suite of high resolution numerical simulations in order to quantify and physically describe the evolution of the thermodynamic structure associated with a typical extratropical transition case, North Atlantic Tropical Cyclone Bonnie of 1998. Thermodynamic budgets native to the numerical model's primitive equation set and physical parameterizations are computed during the transition phase of the cyclone within a four-dimensional analysis framework. The observed warm-to-cold thermal profile evolution is found to arise out of an imbalance between dynamical cooling and parameterized warming contributions. This dynamical cooling, as influenced by horizontal advection, vertical advection and adiabatic cooling, and total divergence, is of greater magnitude than warming associated with latent heat release due to condensation and deposition processes within the transitioning cyclone's delta rain region. While the net thermodynamic evolution is found to be relatively resolution-insensitive, specific details of the thermodynamic balance are found to vary depending upon the horizontal resolution of the given numerical simulation. The thermodynamic evolution is ultimately shown to be a natural outgrowth of the factors that influence extratropical transition as a whole and is found to closely resemble the mature and occluding stages of purely cold-core extratropical cyclone development.
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