Mesoscale convective systems in association with tropical cyclones over Bay of Bengal

The early stages of tropical cyclones (TCs) are extremely complex, and their understanding presents a challenge to researchers worldwide. Better understanding of the role of mesoscale convective systems (MCS) in the formative stage of TC will increase the ability to predict their characteristics including intensification and movement. Objective of the study is to analyze the interaction of multiple mesoscale structures during different stages of TC. In this study, Kalpana-1 half-hourly satellite infrared imageries are used to observe the interaction between MCSs and their environment. Average areas of MCS are calculated based on different cloud top temperatures (CTTs) viz −30, −50, −70 °C and also for different stages of TC based on five TCs during 2010–2012. The analysis has been carried out with respect to variations of (1) number of clusters, (2) distance between the clusters, (3) average distance of clusters from the center of the TC, and (4) area of clusters with respect to intensity (T number) of TC. Results indicate that merger of mesoscale convective vortices is a common precursor event during TC genesis. The average distances between clusters almost remain same during genesis and growing phase, and it gradually decreases during mature phase of TC. Further, there is decrease in the average distance of cloud clusters from the center of TC with respect to increase in intensity up to 2.5–3.5 after that the distance decreases with increase in intensity as the cloud pattern changes to central dense overcast or eye pattern. The average areas of the clusters associated the cyclonic disturbances increases from genesis phase till the intensity reaches T3.0; thereafter, it decreases gradually with increase in intensity. The number of clusters, the distances between them and their average distances from the center of the disturbance, and the total area of clusters show diurnal variations which is more significant during initial stage of formation. The study will be helpful in better understanding of physical processes in diurnal variations of convection and relation between convection and intensity of the storm.