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..

RT @sarakumar1: @weatherofindia cloudy in #chennai south suburbs #Kovilambakkam but no rain. Cool air blowing. http://t.co/ZsRDdrmW 3:44pm

Chennai - After the heavy T.shower, Polichalur zone got strong drizzle from 2am till now 10:20am! Just stopped!!

RT @aknarendranath: @weatherofindia Business Line : Fresh rains forecast as deficit narrows to 9% http://t.co/ojcADcVL

RT @gravikumar:  5:48am #Chennai it was raining lightly for past several minutes and now it's steady and solid pouring in Adyar area.

RT @weatherofindia: RT @muralispeak: @weatherofindia its pouring in nolambur chennai. Powercut too since 2 hours 2:19am

Chennai - strong drizzle continues over Polichalur zone 2:58am

RT @gravikumar: @weatherofindia I was driving from Perungudi to Adyar, #chennai. I could see such a heavy rain now 1.00am. Wow

Chennai - an electric shower is now sweeping Polichalur zone 12:55am

RT @ranganaathan: @weatherofindia Heavy rains in T-Nagar from last 10 mts, looks like roads will be flooded morrow. 12:36am