Abstract
Doppler radar observations of Tropical Cyclone Dina, as its eye passed at less than 100 km from the northern coast of La Reunion 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.
Highlights
Tropical cyclones (TCs) are threatening meteorological phenomena for islands and coastal regions in the Tropics
Apart from geostationary satellite images, real-time data on TCs are relatively scarce and, even when the storm center is at relatively close distance (Յ100 km) from the threatened area, it is very difficult
We show that the ground-based version of the extended VTD (EVTD: Roux and Marks 1996) method—Ground-Based Extended Velocity Track Display (GB-EVTD)—can alleviate this limitation
Summary
Tropical cyclones (TCs) are threatening meteorological phenomena for islands and coastal regions in the Tropics. These perturbations are ‘‘warm core’’ vortices where the strongest swirling winds occur in the lowest levels at some distance from the storm circulation center. Ground-based Doppler radars are essential tools to observe mesoscale precipitating systems and, in addition to providing information on rain intensity, they can be of great help to estimate the wind structure of TCs. Lee et al (1999, hereafter LJCD), Lee and Marks (2000) and Lee et al (2000) have shown that, through the Ground-Based Velocity Track Display (GB-VTD) technique, it is possible to deduce a plausible and physically consistent three-dimensional primary circulation of a landfalling TC using a single ground-based Doppler radar.
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