Structure and Evolution of Intense Tropical Cyclone Dina near La Réunion on 22 January 2002: GB-EVTD Analysis of Single Doppler Radar Observations

Abstract

Doppler radar observations of Tropical Cyclone Dina, as its eye passed at less than 100 km from the northern coast of La Réunion Island (21°S, 55.5°E) on 22 January 2002, are analyzed using the Ground-Based Extended Velocity Track Display (GB-EVTD) technique. This method is an extension of GB-VTD and it allows one to determine the full set of wavenumber-0 and -1 components of the tangential and radial winds in a tropical cyclone from a series of observations with a ground-based Doppler radar. The results obtained for Dina reveal the presence of strong swirling winds (>65 m s?1) at 40?60-km radii from the storm center and below 3-km altitude. The observed changes in the location and intensity of the maximum winds, as well as the veering propagation of Dina, are shown to result probably from interaction between cyclonic winds and high topography of the island.