A study of a typical case of interaction of an easterly wave with a westerly trough during the post monsoon period

Abstract

A spell of heavy rain which first occurred over south India and later gradually spread northwards in the course of about three days during the first week of December 1962 has been studied. An easterly wave which had been affecting south India on 1 December moved out into the Arabian Sea and interacted with a trough in the westerlies which was moving across Rajasthan and northern plains of India in association with a western disturbance. The result of the interaction on 2 December and on subsequent days, which was facilitated by the presence of an induced low in between them, was the formation of an extended trough in the low level easterlies. The northern part of the extended trough in which was embedded the induced low, then moved eastward and got fractured. The fracture of the waves was accompanied by the weakening of the trough systems, as well as the induced low. Unprecedented heavy rains for the month occurred in Madhya Pradesh and Vidarbha and broke the all-time record for the month at a number of stations during and after the formation of the extended trough.