The improvement to the environmental wind and tropical cyclone circulation retrievals with the modified GBVTD (MGBVTD) technique

The ground-based velocity track display (GBVTD) was developed to deduce a three-dimensional primary circulation of landfalling tropical cyclones from single-Doppler radar data. However, the cross-beam component of the mean wind V M cannot be resolved and is consequently aliased into the retrieved axisymmetric tangential wind V to. Recently, the development of the hurricane volume velocity processing method (HVVP) enabled the independent estimation of V M; however, HVVP is potentially limited by the unknown accuracy of empirical assumptions used to deduce the modified Rankine-combined vortex exponent X T. By combing the GBVTD with HVVP techniques, this study proposes a modified GBVTD method (MGBVTD) to objectively deduce X T from the GBVTD technique and provide a more accurate estimation of V M and V TO via an iterative procedure to reach converged V TO and cross-beam component of V M solutions. MGBVTD retains the strength of both algorithms but avoids their weaknesses. The results from idealized experiments demonstrate that the MGBVTD-retrieved cross-beam component of VM is within 2 m s⁻¹ of reality. MGBVTD was applied to Hurricane Bret (1999) whose inner core was captured simultaneously by two Weather Surveillance Radar-1988 Doppler (WSR-88D) instruments. The MGBVTD-retrieved cross-beam component of V M from single-Doppler radar data is very close to that from dual-Doppler radar synthesis using extended GBVTD (EGBVTD); their difference is less than 2 m s⁻¹. The mean difference in the MGBVTD-retrieved V TO from the two radars is ∼2 m s⁻¹, which is significantly smaller than that resolved in GBVTD retrievals (∼5 m s⁻¹)