Easterly wave propagation.

TMD has depicted a high pressure area of 1054 hPa and it is situated in China.

It is powerful and is generating easterly waves.

The wave crest in the ocean / land generates cyclonic circulation.

Where ever wavelets enters with clouds there it rains.[light to moderate]

The severity of cold in Indian East coast especially at WB, Odisha, MP is to be felt and formation of thick fog towards interior west.

Sometime cold wave conditions may also prevail from CAP to head Bay.

Weather Instagram at December 09, 2014 at 05:38PM

Chennai - 2:30pm, a humid day. Intermittent sharp showers possible from tonight. #weather

from Instagram

Weather Instagram at December 09, 2014 at 01:52PM

Bareilly - 12:20pm, dense fog day so far. "Looks like evening". #weather

from Instagram

Easterlies has almost reached Tamilnadu entire coast now ... http://ow.ly/i/7S4EB 
This easterlies is expected to affect most of Tamilnadu coast, S Andhra coast and interior,W Tamilnadu till Friday.. http://ow.ly/i/7S4GX 

Scattered HEAVY T showers expected over central,N,S,W,W-ghats Tamilnadu before midnight today.. http://ow.ly/i/7S4KE 
HEAVY T shower alert for S,S-central Tamilnadu for today!

Wednesday morning...
Scattered moderate rain for most of Tamilnadu coast, Chennai and S-coast Andhra.
Central,N,W,N-W,W-ghats Tamilnadu will gets its share of "heavy" T showers from Wednesday noon to midnight.. http://ow.ly/i/7S4RF 

#Chennai - 1:30pm, a HUMID day. Sharp showers now seen over S-W, 40km from city.
For city Showers expected towards late-evening, midnight.
#Chennai - Can expect a showery morning tomorrow !!
And
Intermittent showers expected to last till Thursday evening.

Weather Instagram at December 09, 2014 at 08:23AM

Chennai - 8:20am, sharp shower now over Meenambakkam zone. #weather

from Instagram