In its official update last Thursday, IMD had said monsoon’s withdrawal was unlikely till September 16 in view of a “deep depression” forming over the Bay of Bengal, which later moved inland from Odisha on Sunday (September 12). Now, another system is expected to sweep in through north Odisha this weekend (around September 18), bringing more rain into central and north India over subsequent days and further delaying monsoon's withdrawal.
This system expected to form over north Bay of Bengal would be the third circulation to invigorate the monsoon this month. In the first two weeks of September, India has received more than 30% surplus rain, halving the overall monsoon season deficit from 10% in late August to 5% till Tuesday.
The deep depression that had crossed Odisha on Sunday, currently lies over north Chhattisgarh as a depression.
The active monsoon conditions this month, after August ended with a 24% deficit, coincide with the Madden Julian Oscillation moving into a position that's normally favourable to the Indian summer monsoon. MJO is an eastward travelling pulse of cloud and rain that impacts tropical weather systems across the globe.
Besides, active monsoon conditions over the northwest Pacific Ocean have also aided September rainfall. “Till August-end, no cyclone developed over that region for 41 days. As a result, we didn’t have any remnant system from the east coming over into the Bay of Bengal. This month, the situation has changed,” the IMD chief added.