Tropical cyclones in the Bay of Bengal and deterministic methods for prediction of their trajectories

Abstract

Based on information about tropical storms and depressions in the Bay of Bengal over a 100-year period (1877–1976), certain climatic characteristics of tropical cyclones are examined. A brief description of climatic parameters, notably the region of their development, direction and nature of movement and percentage of disturbances intensified into severe tropical storms in different seasons of the year, which are explicitly or implicitly related to the formulation of objective methods for forecasting storm tracks, is presented in this work. A brief review of objective methods (numerical and statistical) used for forecasting the tracks of cyclonic storms and the rationale for development of such methods are described. Two numerical methods based on integral and steering flow concepts and four different physical-statistical methods, which take into consideration the influence of both external and internal forces responsible for the movement of tropical cyclones, are developed for forecasting the trajectories of post monsoon cyclonic storms in the Bay of Bengal. Performance of these six objective methods are illustrated through the study of a homogeneous sample of cyclonic storms (14 cases) in the Bay of Bengal during the post monsoon seasons of 1975 and 1976. These results are compared with those obtained from some of the existing methods for forecasting the movement of tropical cyclones in the Bay of Bengal. Finally, the limitations and prospects of objective methods in predicting the tracks of cyclonic storms in the Bay are discussed.