The southwest monsoon has withdrawn from most parts of the country. The line of withdrawal passes through Karwar-Goa on the western side and Guwahati on the eastern end. It is expected to vacate the remaining parts of Northeast India in a day or two. The monsoon stream will simultaneously pull out from the left-out portions of Chhattisgarh, Odisha, and Telangana. This will clear the way for the onset of the northeast monsoon, popularly known as the winter monsoon.

The southwest and northeast monsoons cannot co-exist as a norm. The exit of one and the entry of the other can, however, occur concurrently. There is a track record of such events in the past as well. It was on a day when both monsoons acted simultaneously — the southwest monsoon completely withdrew from the country, while the northeast monsoon commenced over Tamil Nadu on 16th October 2019.

The mandatory conditions for the onset of the northeast monsoon include:

• Withdrawal of southwest monsoon up to 15°N Latitude
• Onset of persistent surface easterly winds over Tamil Nadu Coast
• Depth of easterly winds up to 5,000 feet over Tamil Nadu Coast
• Fairly Widespread rainfall over Coastal Tamil Nadu, South Coastal Andhra Pradesh and adjoining areas

The northeast monsoon onset is not declared before 10th October, even if the above conditions exist (not the case this time). The normal date for the onset of easterly/southeasterly winds is 14th October, and the normal date for the northeast monsoon onset is 20th October. A delay or advancement of about 10 days is quite common.