A Vortex Removal Algorithm for Numerical Weather Prediction Model Tropical Cyclone Applications

Within the WRF-ARW [Skamarock et al., 2005], a TC vortex dynamic-initialization (DI) procedure, motivated by the innovations first presented by Kurihara et al. [1993] and Kurihara et al. [1995] and later implemented with the operational Geophysical Fluid Dynamics Laboratory (GFDL) TC prediction model, has been developed. This methodology offers an advancement beyond that of the GFDL scheme using grid-spacing invariant filtering techniques to remove the 3-dimensional kinematic and thermodynamic attributes of the analysis (first-guess) vortex prior to using near-surface wind-field analyses to construct the initial TC vortex. We present DI experiments where the initial condition for the TC vortex has been assimilated by (a) directly inserting into the filter global analysis, (b) nudged toward an initial state which matches the observed maximum wind-speed intensity, and (c) nudged toward an initial state that conserves the synoptic-scale mass and momentum balance while not necessarily matching the observed value for maximum wind-speed intensity. The consequences of each are presented through an evaluation of the TC track and intensity time-series and also an evaluation of the synoptic-scale adjustments (i.e., gravitational-wave impacts) which occur following the DI procedure.