During the SE/SW monsoon, the dominant quasi-stationary flow pattern of the lower troposphere over much of the Indian Ocean is characterised by a flow pattern often referred to as a DRIFT flow.

Mathematical description of the flow using particle dynamics was first given by Gordon (1953) and later by Johnson and Morth (1959). Although the pattern of their solutions resemble the actual flow, yet computed wind speeds give unrealistic estimates with the consequence that their analytic results could not be used for estimating derived quantities such as divergence and vorticity.

This paper gives a mathematical description which is partly based on empirical results pertaining to the flow. The description is free from the defects of Gordon, and of Johnson and Morth models.