Initialization of Tropical Cyclones in Numerical Prediction Systems

Initialization of tropical cyclones (TCs) is critical for TC predictions in operational numerical prediction systems, especially the intensity change. In this study a TC initialization scheme, identified as the TC dynamic initialization (TCDI) package, is developed that can be used in numerical prediction systems for TC prediction. The TCDI package includes two major components. The first part is the removal of the TC vortex in the initial field of the numerical model. The second part is a dynamic initialization of the TC vortex spun up with the full nonlinear dynamics and physics. During the spin-up period, the TC vortex is forced toward either the best track estimate central minimum pressure or wind structure. The dynamic and thermodynamic balanced TC vortex is then added back to the initial field.

The TCDI initialization package was tested in the Navy COAMPS-TC system on multiple TCs during the 2008 and 2009 North Atlantic and Western North Pacific hurricane seasons. Intensity errors were reduced by approximately 5 knots over all lead times, with even more significant improvements at the early lead times. The dynamic initialization procedure was shown to produce a more realistic TC structure and warm core as well. Further plans in this study include implementation of adjusting the heating in the vicinity of TCs to the satellite retrieved heating profiles during dynamic initialization, optimization of the TCDI package, and testing of the TCDI in an operational environment.