Rainfall Distribution

First, originate in the Bay of Bengal causing rainfall over the plains of north India.
Second is the Arabian Sea current of the southwest monsoon which brings rain to the west coast of India.
Much of the rainfall along the Western Ghats is orographic as the moist air is obstructed and forced to rise along the Ghats.
The intensity of rainfall over the west coast of India is, however, related to two factors:
The offshore meteorological conditions.
The position of the equatorial jet stream along the eastern coast of Africa.
The frequency of the tropical depressions originating from the Bay of Bengal varies from year to year. Their paths over India are mainly determined by the position of ITCZ which is generally termed as the monsoon trough.
As the axis of the monsoon trough oscillates, there are fluctuations in the track and direction of these depressions, and the intensity and the amount of rainfall vary from year to year.
The rain which comes in spells displays a declining trend from west to east over the west coast, and from the southeast towards the northwest over the North Indian Plain and the northern part of the Peninsula.