Chennai - 6:40pm, Strong drizzle now. First rain due to S-W Bay LOW "95B". More coming up around midnight, early hrs. http://ow.ly/i/85exT 

6:30pm, Deep convective activity seen around S-W Bay LOW "95B" and over its Northern band ... http://ow.ly/i/85eCe 

Karaikal - 2pm, it's been drizzling continuously with an occasional moderate shower.

RT @Serene_Meadows: @weatherofindia Delhi all fogged out this morning. Easily the worst fog of this season. 8:22am

RT @rajugana: @weatherofindia Bangalore 10.00am.. Foggy, chilly, lazy Sunday..cloudy skies..a pic http://t.co/4SHGjOq2yu

From morning, showers seen over Central coast Tamilnadu... Now rain slowly creeping to N coast Tamilnadu.

Chennai - 1:15pm, again a cloudy day and bit humid, warm than yesterday. Rain nearing from SE, drizzle will push in after 4pm.

95B - S-W Bay Low - What next ??

At present, a low,mid-level circulation is seen over a Sea level LOW pressure system over S-W Bay near to East Srilanka coast.

Present pressure is around 1004mb
And location is 7.5N , 83.3E.

GFS model doesn't expect the system to deepen to Depression (or) move North or N-W before Monday morning. And after that, it'll deepen to a Depression or Well marked LOW and drift into central Tamilnadu coast on 30-Dec.

NAVGEM model almost similar to GFS, expects the system to become Well Marked LOW on Monday and drift into central Tamilnadu coast on 30-Dec.

On Tuesday, 30-Dec... an upper-level W.D trough is expected to drop upto 21N along S Pakistan, W,N-W Gujarat. This is expected to drift East into India in subsequent days, this can make the S-W Bay system to drift North initially and then N-E along S-E coast of India into N Bay.

According to GFS, Showers will reach central,N Tamilnadu coast and even Chennai after morning or noon of Sunday, 28-Dec.
On Monday, HEAVY rain expected along central,S-E,N Tamilnadu coast and moderate rain into Chennai.

Weather Instagram at December 27, 2014 at 07:29PM

Mahabalipuram - 3:38pm, slightly foggy, mild, breezy and cloudy. #weather

from Instagram

RT @rajugana: @weatherofindia Bangalore 3.45pm, After a hot and breezy day, now the sky appears partially cloudy with high broken clouds...

Important update regarding SW bay low and circulation 95B, and its impact for Tamilnadu... Coming up at around 9:30pm !

Weather Instagram at December 27, 2014 at 01:20PM

Chennai - 1pm, slight foggy, cloudy. Breezy and temp at 28 C. #weather

from Instagram

Posted Friday Night: BB-15 

A Low has formed in the Southern Bay estimated at around 5.5N and 84.4E. In the 700 hpa trough now, expected to deepen from the current status and embed another Low (BB-15) in the 500 hpa trough by Sunday. 

Upper Jet Streams indicate a core around the TN coast. Meanwhile, in the Pakistan/NW India region, the 200 hpa jet streams are expected to get a Southward dip due to rushing in of Northern cool winds pushing in. 

Resultantly:

1a). The core in the jet streams of the Sub Tropical Ridge situated off the TN Coast will "move" Eastwards. The core, or the clockwise winds at 200 hpa, will circulate clockwise off the TN/AP coast. 

2b). The dipping of the jet streams Southwards, will take a "plunge" upto Sindh/Gujarat regions. 

Hence, due to 1a): The Low, BB-15, will strengthen, but will as a depression at around 998 mb, just miss and skirt along the TN coast and AP coast. Rainfall will be more concentrated in the waters. Chennai and TN coast will get rainfall from 30th. 

BB-15 will skirt the coast and move N/NE along the track.

Odisha can expect showers on Tuesday 30th.

2b): Will bring colder conditions in Northern Pakistan, Sindh, NW India and Rajasthan and Gujarat. All this from 30th December. Around freezing night temperatures from 30th in North Rajasthan, Punjab and Haryana. Similarly, very cold temperatures in Pak Punjab and Sindh.

Meanwhile, Saturday and Sunday will see rains in Southern TN . 

For Mumbai, Partly cloudy Saturday. The current pleasant nights will continue, and Weekend will see day around 32c, but a pleasant night with low around 15/16c. 

Pune will have a cool climate with partly cloudy Saturday and day at 26c. Lows around 9c.

Delhi. Days will be foggy, at around 17c. Sunday night will see a drop to 5c.

Chennai, rains increasing from Tuesday 30th.

Thunder showers expected in Thiruvananthpuram this weekend. Kochi will however be cloudy.

Easterlies continue to affect E,S-E Srilanka ... a mini circulation is seen over S-S-E Bay just above 5N.

On 25-Dec, Christmas day, this circulation is expected to become strong over South bay above 5th parallel.. http://ow.ly/i/83b92 
GFS expects this system to become Depression / Cyclone and drift N-W upto central Tamilnadu coast on 28/29-Dec.. http://ow.ly/i/83bjd 
A mid,upper-level W.D trough travelling East over North India can make the upcoming cyclone to drift N-E on 29-Dec http://ow.ly/i/83btu 

NAVGEM suggests, that circulation will pop along S-E srilanka coast, move N-W and cross central Tamilnadu on 27-Dec http://ow.ly/i/83bEX 

Remember In 2011, Cyclone Thane also started as a circulation on 25-Dec and tracked N-W then W to hit central TN... http://ow.ly/Gmx7e 

Meanwhile, next 2 days - partly cloudy, dry days and cold morning expected for N,central Tamilnadu and cloudy, warm day for S,S-E Tamilnadu.
Chennai - Morning temp expected to be around 20/21 C for next 2/3 mornings.
Day will be around 28 C, more DRY and partly cloudy.