Features of South West Monsoon Withdrawal and the advance of the North East Monsoon:
This note is not a forecast nor a quantum estimate. It is just how to begin a Monsoon Watch for the NEM.
In the very initail para, we begin with the basic fact of the Monsoon origins. SWM has its origin around the Mascarene Highs off Madagascar, and the NEM has its origin round a large anticyclone over Siberia.
However, coming to the advances of these systems, the mode of setting of the 2 monsoons differ. The onset of SWM is well defined, and follows progressively Northwards.This can be monitored quite accurately on weather charts.
On the other hand the onset of the NEM is not clearly defined. In fact, in some years, there has been no clear indication between the withdrawal of the SWM in peninsula India and the onset of the NEM.
I would, on the above point, normally hesitate to actually present or believe a "normal date" for the onset of the NEM in the Southern States.
Full Article with details of NEM in Vagaries..