Evaluation of Tropical Cyclone Center Identification Methods in Numerical Models

Identifying the center of a tropical cyclone in a high resolution model simulation has a number of applications in the operational and research communities, including constructing a track, calculating azimuthal means and perturbations, and diagnosing vortex tilt. Various methods of defining the tropical cyclone center have been used in the literature, including (but not limited to) the pressure or geopotential height minimum, maximizing the tangential component of the wind at the radius of maximum winds, and the potential vorticity centroid. This study will evaluate several methods in a high-resolution Weather Research and Forecasting (WRF) model simulation of a highly sheared, intensifying, asymmetric tropical cyclone. The simulated tropical cyclone (TC) contains downshear local convective cells with associated mesovortices embedded in a broader TC vortex, complicating the identification of the TC vortex center. We will show that the pressure centroid most accurately diagnoses the TC vortex center, and unlike other methods, yields a coherent vertical structure of TC vortex tilt that curves clockwise with height. We will propose a method that chooses the optimum radius for the pressure centroid calculation, and we will assess the sensitivity of the pressure centroid to the radius used.