With a day to go for the season, the rain deficit during monsoon 2015 has slipped back to 14 per cent on Tuesday, two per cent higher than estimated by the India Met Department.
This emerged after a late surge over Peninsular India and parts of North-West seems to have run out of steam.
Also, the monsoon has resumed withdrawing from north-west and adjoining Central India.
The withdrawal line passed through Dharchula, Etawah, Guna, Ratlam, Ahmedabad and Dwarka on Tuesday, the Met said.
But the monsoon held on its own over parts of the South, including in Tamil Nadu, Puducherry and Andaman and Nicobar islands. This indicates that withdrawal from the entire landmass will be delayed beyond September, in line with the trend observed in the recent past.
‘Low’ forecast Additionally, a rain-generating low-pressure area is expected to be thrown up over the Andaman Sea after a ‘monsoon pulse’ from across the seawaters meandered in and has started evolving there.
Model forecasts do not indicate the formation of a major weather system (depression/cyclone) but the ‘low’ may wander about in the Central Bay of Bengal and trigger a surge of flows across southern peninsula.
The net result will be enhanced rain along the West Coast and the East Coast and parts of interior peninsula for the next two weeks, a bulk of which may fall beyond the scope of the southwest monsoon.
The trigger is being attributed to the evolving positive phase of the Indian Ocean Dipole (IOD) in which the western part of the Indian Ocean warms up relative to the East, but late for the current monsoon.
Beneficial impact A positive phase of the IOD has traditionally had a beneficial impact on the concurrent Indian monsoon.
An Australian Bureau of Meteorology update said that the positive IOD is evolving to be the strongest one after the year 2006 event, first time in the history when it was replicated in three successive years.
Meanwhile, the late rains happening in the South may get accounted for in the North-East monsoon that sets in normally in the October 15-20 time band.
Model forecasts show that the monsoon reverse might reach fringes of South China Sea upstream by October 11.
According to latest forecasts by the US Centre for Climate Prediction, the West Coast, the East Coast and parts of interior peninsula may stay wet right until mid-October.