Southwest Monsoon will resume withdrawal very soon from remaining parts of Northwest India and Central India. It is expected to take big leap and vacate Eastern parts and Northeast India during next week. Parts of Odisha, Chhattisgarh and Maharashtra are likely to be the last bastion of Southwest Monsoon holding for the next 5-6 days. The moment it vacates these parts, favorable conditions seem to be building up for arrival of Northeast Monsoon.
Southwest Monsoon and Northeast Monsoon do not co-exist. Southwest Monsoon has to make exit essentially before entry of Northeast Monsoon. At best, entry and exit of the respective monsoons can be simultaneous, as it happened last year. Announcement of onset of Northeast Monsoon has to compulsorily meet certain meteorological conditions. Four such conditions are as listed.
Northeast monsoon onset is not declared before 10thOctober, even if conditions described exist. Normal date for onset of easterly/southeasterly winds is 14thOct. Based on long term data, 20thOct is considered as normal date for onset of northeast monsoon and +/- 5days is considered standard for the winter monsoon.
Bay of Bengal is going to be active basin, commencing next week. Series of weather systems are lined up originating far in the ocean and travelling eastward, stretching across the 2 ends of Bay of Bengal. Meteorological conditions seem to be favoring timely onset of Northeast Monsoon.
