Diagnostic Study of Deep Depression over Northwest Bay of Bengal in June 2011: A Case Study

Abstract

A Deep Depression (DD) was formed over North-West Bay of Bengal during (16-22) June 2011 and its gradual movement caused the Southwest monsoon 2011 to cover most parts of the country outside western parts of Rajasthan and north Gujarat state. The unique feature associated with this DD was that the life of the system was longer and movement was slow. Various diagnostic features associated with life period and movement has been analysed and discussed. This study highlights that the system has given heavy to very heavy rainfall together with some exceptionally heavy rainfall along its path. As a result of this, the rainfall distribution of June 2011 along its path has been excess. The analysis of the synoptic condition revealed that the absolute vorticity for the system was very strong. After the landfall the continuous supply of moisture initially from the Bay of Bengal and after that the strong moisture incursion from the Arabian Sea has been responsible for the longer life of the system upto Madhya Pradesh. Moreover, after landfall it comes under the influence of mid & upper tropospheric westerly wind which may be responsible for slow movement of the system.