Dynamic Initialization for Tropical Cyclone Intensity Prediction

Accurate initialization of tropical cyclones (TCs) in numerical prediction systems is critical for the subsequent intensity and structure prediction. In this study, we develop two dynamic initialization schemes that can be used in TC numerical prediction systems. The first scheme, identified as the TC dynamic initialization (TCDI) package, includes two major components. The first part is the removal of the TC vortex in the initial field of the TC forecast system. The second part is a dynamic initialization of the TC vortex spun up offline with a full nonlinear dynamics and physics in a quiescent environment. During the spin-up period, the TC vortex is forced toward either the best track estimated central minimum pressure or the wind structure. The dynamic and thermodynamic balanced TC vortex generated by the spin-up process is then added back to the initial field of the forecast system. Note that the model used for offline spin up does not have to be the same model as the TC forecast system. The second approach, identified as the dynamic initialization (DI) scheme, involves a forward relaxation period of 12 hour when the entire three dimensional wind fields are nudged to the initial winds prior to the start of model integration. Both schemes are tested on multiple TCs from 2009-2011 using the Navy's Coupled Ocean/Atmosphere Mesoscale Prediction System – Tropical Cyclones (COAMPS®1-TC). The track and intensity prediction evaluation of each scheme with the control 3DVAR initialization is presented.