Extended Velocity Track Display (EVTD): An Improved Processing Method for Doppler Radar Observations of Tropical Cyclones

Abstract

The authors present an improved version of the velocity track display (VTD) method, proposed by Lee et al., to deduce the primary vortex circulation in hurricanes from airborne Doppler radar data obtained during straightline legs through the storm center. VTD allows the derivation of one projection of the mean horizontal wind, the wavenumber 0, 1, and 2 components of the tangential wind and one projection of the radial wind, in a series of concentric rings centered on the storm circulation center. The extended VTD (EVTD) algorithm determines additional information through a combination of data collected during successive legs: the Cartesian components of the mean horizontal wind; the wavenumber 0, 1, and 2 components of the tangential wind; and the wavenumber 0 and 1 components of the radial wind. Application of EVTD to airborne Doppler data collected on 17 September 1989 in Hurricane Hugo is discussed. Comparisons between the EVTD-derived winds, the flight-level measurements, and winds deduced from ?pseudo-dual-Doppler? analyses show qualitatively good agreement. These results reveal the asymmetric structure of the storm and show that it was in a deepening stage, with increasing tangential wind, inflow, and upward velocity. Further applications are finally discussed.