An analysis of Typhoon Chanthu in June 2004 with focus on the impact on Thailand

In this paper, the influence of Typhoon Chanthu on Thailand during June 2004 was studied. Several major features have been revealed. (1) Chanthu formed and developed in favorable large-scale conditions. A continental high-pressure system covered most of China and merged with the West Pacific Subtropical High to become a west-east oriented high-pressure band, which was responsible for the westward movement of the typhoon. (2) There existed a stationary and active ITCZ, which was the preferred formation area of the typhoon. The ITCZ extended from the Bay of Bengal, through the Indo-China Peninsula and the South China Sea, to the western Pacific. Chanthu formed in the ITCZ and moved almost directly along it. (3) The moisture sources differed during the various stages of development. In the earlier stages, water vapor came largely from the South China Sea but in later stages, the source was mainly from the Bay of Bengal. The rich water vapor supply explains the long-lived effects of Chanthu and its remnants after landfall. (4) Cyclonic circulation remained following the landfall of Chanthu, as did a weak warm core in the upper-middle troposphere, which was likely caused by the release of latent heat from convective condensation. Due to the ample moisture supply from the ITCZ, convective activity was still very active after landfall. (5) Subgrid-scale convective systems played an important role in the kinetic energy budget. In addition, numerical simulations show that, among various cumulus convective parameterization schemes, the Betts-Miller-Janjic scheme seemed to be the best in the summer season.