Vector correlation between modeled gradient wind and observed high-altitude wind of a translating tropical cyclone

This study investigated the validity of three existing gradient wind models for a translating tropical cyclone by analyzing vector correlations between the modeled gradient wind and the observed wind. Modeled gradient wind vectors were computed using the three models used or proposed by Georgiou (1986), Yoshizumi (1968), and Wang et al. (2017). For the observed wind, we used high-altitude wind profiler data obtained during the passage around Japan of Typhoon Faxai 2019 and Typhoon Haishen 2020. Of the three gradient wind models studied, the one used most commonly, i.e., that of Georgiou, yielded the lowest correlation coefficient. The gradient wind model of Wang et al. generally yielded the highest correlation coefficient among the three models, with the least deviation from the observed wind in terms of both wind speed and wind direction. The performance of the three gradient wind models was found consistent with the magnitude of the residuals in the momentum conservation equation, and with the case study results for two hurricanes presented in our previous study.