A Study for Determination of the Low Level Circulation Center of Tropical Cyclones in a Weakening Stage with Emphasis on Microwave and Radar Observations

In the Korea Meteorological Administration (KMA)'s operational forecast of tropical cyclones, accurate analysis and determination of low level circulation centers (LLCCs) from various available data such as satellite, radar, and synoptic observation, especially at their weakening stage around the Korean Peninsula, are very important because the consequent result may affect the landfall time and location of tropical cyclones. But it is very difficult to analyze LLCCs in a given time exactly. Satellite-based microwave images sometimes show better LLCCs than geostationary infrared or visible images. Unfortunately the temporal availability of microwave channel data is limited. On the other hand, the ground-based radar data is very useful to analysis LLCCs because they sometimes show clearer image with higher time resolution (every 10 minutes) as well as quick data acquisition. In this study, we carried out some case studies to determine the LLCCs of the following typhoons, Kompasu (1007), Khanun (1207), Tembin (1214) and Bolaven (1215). Features from each observation data are presented and compared with final determination of the LLCCs according to each weakening stage and type.