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Abstract

This study evaluated the feasibility of applying a vortex relocation scheme based on a synthetic vortex in the Numerical Tools for Hurricane Forecast (NTHF) system, operating in the Department of Meteorology of the Higher Institute of Technologies and Applied Sciences, University of Havana. Hurricanes Dorian and Lorenzo and the tropical storm Karen were selected as case studies. The synthetic vortex in the entire vertical column was extracted from the NTHF simulations initialized with the GDAS (Global Data Assimilation System) outputs at 0.25 of the horizontal resolution of the 6 hours previous cycle. The new vortex replaced the vortex in the initialization fields of NTHF obtained from the forecast outputs of the global GFS (Global Forecast System) model at a horizontal resolution of 0.5 degrees. In all cases, the simulations were initialized at 0000 UTC with the boundary conditions updated every 6 hours. The results revealed that the vortex relocation scheme represented a more structured tropical cyclone (TCs). Nevertheless, the dynamic instability caused by the introduction of the synthetic vortex in the background field conditioned that the center of the TCs developed in a drier environment and the center of the system was colder, which led to an increase in the mean errors in the track and intensity forecast, concerning the experiments without vortex relocation.

Keywords: NTHF; tropical cyclone; vortex relocation; synthetic vortex; initialization; forecast.