DISTRIBUTION STATEMENT A. Approved for public release; distribution is unlimited. 2012 ANNUAL REPORT FOR ONR SPONSORED RESEARCH: Continued Analysis on Multiscale Aspects of Tropical Cyclone Formation, Structure Change and Predictability in the Western North Pacific Region as Part of the TCS08 DRI Michael T. Montgomery, Principal Investigator Michael M. Bell, Co-Principal Investigator Department of Meteorology Naval Postgraduate School Monterey, CA 93943 Phone: 831-656-2296 Fax: 831-656-2736 Email: mtmontgo@nps.edu ; mmbell@hawaii.edu Award Number: N0001411WX20095 Montgomery Research Group Website http://met.nps.edu/~mtmontgo LONG-TERM GOALS AND OBJECTIVES The overarching objectives of this research project are to obtain an improved understanding of the formation, intensification, predictability and structure change of tropical cyclones in the Western Pacific region. These new insights will ultimately improve forecast guidance for U.S. Naval operations in this region. APPROACH During this past year the PI and his research group have developed and further substantiated a new model for the phenomenon of secondary eyewall formation (SEF), a process that occurs frequently in mature tropical cyclones and is a continued forecast priority for storms threatening Naval and DOD operations in the Western North Pacific sector. The new model is based on a newly articulated paradigm of tropical cyclone intensification (discussed further below) that the PI has developed in collaboration with his distinguished international colleague, Professor Roger Smith from the University of Munich. Because of space constraints, only pertinent background information is provided to explain the basis for the new approach followed by a summary of some of the key new findings on the SEF problem. Other research supported by this grant is discussed in preceding annual reports and via the PI’s website listed above. Recent developments in tropical cyclone intensification theory A new paradigm of tropical cyclone intensification and hurricane boundary layer dynamics has been developed by the PI and his distinguished scientific colleague, Professor Roger Smith. The intensification paradigm begins with the recognition of the inherent three-dimensional nature of the intensification process and emphasizes the aggregate effects of the rotating deep convective structures that drive the spin-up process (Nguyen et al. 2008, Montgomery et al. 2009, Smith et al. 2009, Bui et al. 2009, Montgomery et al. 2010, and Fan and Zhang 2010). From the standpoint of the mean-field dynamics, which is associated with azimuthally averaging the three-dimensional state variables around the system circulation center, the rotating deep convective structures have been implicated in two mechanisms for spinning up the mean vortex: