Impacts of Bogus Vortex Initialization Using Scatterometer-Derived 34 kt Wind Radii and Centers on Tropical Cyclone Forecasts

This study demonstrates the positive impact of scatterometer wind-based bogus vortex initialization on forecasts of Typhoon Doksuri (2023). In this scheme, the NCEP analysis vortex in the initial conditions is replaced with a bogus vortex. A regression model links the scatterometer wind-derived 34 kt wind radius with the radius of maximum sea-level pressure gradient, a required parameter in Fujita’s bogus formula. The cyclonic circulation center identified in the scatterometer wind field is designated as the typhoon center. The resulting bogus vortex provides a more realistic representation of the low-level circulation, center location, and intensity. Numerical experiments with the WRF model, configured with two-way nested domains (9–3 km) and 115 vertical levels below the model top at 1 hPa, show that the scatterometer wind-bogus scheme effectively improves the initial vortex position and minimum sea-level pressure, slightly enhances track forecasts, and substantially improves intensity forecasts, particularly during rapid intensification and weakening stages of Typhoon Doksuri over the western North Pacific. Furthermore, comparisons with Himawari-9 AHI infrared observations indicate that forecasts with bogus vortex initialization better reproduce the eye, eyewall, and spiral rainband structures than forecasts without it. These results underscore the value of scatterometer observations for improving typhoon forecasts.