Intensity Measurements of a Landfalling Tropical Cyclone Using Conventional Coastal Weather Radar

Abstract

Tropical cyclone (TC) intensity observations considerably improve forecast models. They are particularly used to continuously measure TC intensity for landfalling cyclones to improve their forecast. For example, TC Irving, which operated in the Gulf of Tonkin, South China Sea, on 23–24 July 1989, was observed by a conventional weather radar installed at the Phu Lien Observatory in North Vietnam. The maximum wind speed was calculated by the hyperbolic-logarithmic approximation (HLS-approximation) of spiral cloud-rain bands (SCRBs) of recorded TC radar images. The data spanned about 15 h. Ground-based estimates of the cyclone intensity were obtained from pressure measurements at two coastal weather stations. A comparison of these estimates with the HLS wind resulting from the HLS approximation of SCRBs showed satisfactory synchronization. In particular, radar and meteorological data indicated cyclone intensification near landfall and rapid cyclone intensification after landfall. Both intensifications were accompanied by polygonal eye shapes. This study demonstrates the feasibility of using the HLS-approximation technique for retrieving TC intensity variation from conventional weather radar data.