East-West trough with system   embedded..(as per post below)** 
http://www.imd.gov.in/section/satmet/dynamic/insatsector-irc.htm.....image of 1400Z  1st November

Thursday @ 5.30 am IST:  
BB-10, a depression now, is centred at 13.8N and 77.5E. According to my estimate and imagery study, the centre is about 100 kms North of Bangalore, between Bangalore and Anantpur. 
At 998 mb, with core winds at 35 knts, the confusion amongst readers of vagaries is the mass clouding in the East. 

The spiral circulation has "stretched" to the east due to "fixation" in the East-West trough. The trough seems to be tilted to the East, as of today morning...

Forecast below...

Posted @ 11.45 pm Wednesday:
Cyclone Nilam is gone and its a Deep Depression now. So, we'll come back to BB-10.

Current Position at 11.00 pm shows it at 13.3N and 78.2E , near  Kolar in Karnataka, and movement W/NW thru Tumkur.

Chennai rainfall decreases by Friday (15-20 mms), and will be down to between 7-10 mms/day Saturday/Sunday. 

**BB-10 tracks W/NW, and soon gets embedded in an East-West trough along the Maharashtra-Northern AP-Northern Karnataka line. This trough will extend into the upper levels at least till 850 hpa.

Forecast Thursday 1st November- Friday 2nd November: 
Rainfall can be expected all along this trough line, with the heavier falls in the region the BB-10 system is embedded. Hence precipitation spreading into interior Karnataka, Northern AP and Southern Maharashtra, Western Vidharbha and Marathwada. 
Light/medium rains drifting into Konkan and coastal Karnataka.

Saturday 3rd November: If the trough and BB-10 remain intact and sustainable (which is questionable as it is not the season), we may see some enhanced rainfall along the Konkan belt.  If they have faded, then decrease in rainfall in the above mentioned regions.

(Indications for Mumbai observers in next 2 days if the trough is sustaining. Easterly winds in Mumbai will change to SE or S if its sustains).

We may even chance a guess of the system leaving the rough and sliding into the Arabian Sea on Saturday (50% chance)..hence we wait and observe...

Mumbai City: 
Thursday 1st: Partly cloudy and hazy. Medium clouds from evening..
Friday 2nd: Partly cloudy. Light drizzles expected in some parts...rains upto 5 mms
Saturday 3rd: Cloudy, and cooler. Light rains, with medium heavy showers in some areas. Rains 5-10 mms. (tentative)

Pune: Thursday/Friday/Saturday: Cloudy with light rains upto 5 mms/day in different areas.Chance of a bit more on Saturday.

Kolkata remains stuffy on Thursday and Friday, finally getting showers on Saturday.

Northern Sub-Continent:
North of the trough line, the winds will be Easterly, and South of the system winds will be S/SE.
The trough, as it gets strengthened by the system, will see stronger N/NE winds. Result: Goodbye to O-3. It will never allow O-3, which was precipitating rains even in Dubai few days ago, will just dissolve in the far North.
But, a resulting high pressure in its place will bring clear weather and low temperatures in Northern India. 
In fact, even Pakistan's central and Northern regions see a fall in night temperatures.


Maharashtra Rainfall figures, Cumulative till End October..compiled (as usual) by GSB..on Stats Page 

Next Update..11.30 pm
Cyclone Nilam Update:
Position @ 10 pm IST Wednesday:

System has moved inland, comparitevly fast. and at the time lies 12.8N and 78.5E, West of Arcot, near the Karnataka border. Its centre is now 120 kms East from Bangalore.
Strength at 989 mb and core winds down to 45 knts now..soon to become a Deep Depression.

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Position as at 7.00pm IST:

Cyclone Nilam made Landfall between Puducherry and Chennai, in Southern Kanchipuram District around  6.30pm IST Wednesday. It crossed land at 979 mb with winds gushing at 60 knts , that is 111 kmph.

Now, it is moving fast inland and very gradually weakening. Located at 12.8N and 80 E. That is , it has moved due North inland, and is now proceeding towards Kanchipuram City. Centre is just about 45 kms SW of Chennai.

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Position as at 3 pm IST:  Nilam centre now just 20 kms SE off Puducherry...almost about to strike land between Cuddalore and P'Cherry. At 979 mb, and 61 knts, clouds suddnely gaining height. CTT now -85c at centre.

Position 2 pm IST: 50  kms SE of Cuddalore. winds 65 knts ,pressure 976 mb

Position as at 12 noon Wednesday:   

Tracked NW and is about 120 kms East of Karaikal and 250 kms SE of Chennai at 11N and 80.8E. Movement NW and core centre will hit land near  Cuddalore. Maximum winds and damage areas shown in grades.
Core winds gushing at 65 knts


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Position as at 9.00 am IST Wednesday:
Tracked very slightly W/NW since last vagaries' report of 0000 hrs. Now at 10.6N and 81.3E..having shifted just about  35 kms in that direction..pressure at 987 mb and peak winds  increased to 65 knts now, and cloud top temperature at -82c.

Next Update at 11.30 am IST

Interesting Cyclone history of Chennai provided by Pradeep on Inter Active Page of this blog..

Position as at 0000 hrs Wednesday: Tracked W/NW and is now at  10.0N and 81.6E. Core pressure 989 mb and winds gushing at 60 knts..cloud top temperatures at -85c, coinciding with central temperatures...

Posted @ 10.30 pm Tuesday:


A back-and-forth game !
Now, BB-10, "Nilam", has retracked in the last 6 hrs to move slightly westwards at 6 knts/hour, and has regained itself at 993 mb, with 45 knts winds. Currently located centre at 8.8N and 82.0E. 

Mostly all international forecast models project it to move NW , and the models aim at almost at Chennai. All models have changed the colour of the forecast dramatically...all eyes on Chennai they say !

AS-2 is comfortable at home at the local address, 9.4N and 72.2E...but at 1006 mb. Will track W/NW...

Madhya Maharashtra Cold: Sudden fall in humidity from NE winds in early evening hours, and a temporary clear sky later at night, created an ideal condition for maximum outgoing heat radiation in the night. Resulting in a sharp fall in the night temperature. The loss of heat due to radiation into space was at night, and continued till sunrise, resulting in the coolest temperature before sunrise. This is common for interiors during winter clear nights.


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Synoptic Situation as on Tuesday 11.30 am IST:

BB-10 (Deep Depression), it seems, has changed its mind. It is refusing to cross land, and has turned its back on Sri Lanka, after coming to within 50 kms from its shores !

Now at 8.8N and 83.4E,, its showing an "undecided" course. It has moved 100 kms Eastwards. Obviously it is troubled by the high pressure ridge in the upper levels which has descended to 14N.  
Expected track: Same,westwards with very marginal North deviation.

But, the intense convective clouding shows no sign of any trouble, as it is now covering areas along Sri Lanka and adjoining TN coasts, with cloud top temperatures at -85c. Core pressure at 996 mb and core winds at 40 knts.(Deep Depression).

Latest (12 noon): It (BB-10) has moved West again, and is at 8.4N and 82E..moved 110 kms back to yesterday's position.

Our other friend across the peninsula, AS-2 (Low) has found home in the 6N and 71.5E regions.


Sudden Cold in Madhya Maharashtra.
Nashik showing min temp of 11.2 C,  Shirdi (AWS) 11.5 C,  Pune 12.7 C. Aurangabad and Nagpur were 14.2c.
Mumbai Scruz was 20.4c.

Posted @ 11.45 pm IST Monday: 
BB-10 about to hit Sri Lanka...

In the last 6 hrs (since vagaries' report), BB-10, a deep depression, remained at 996 mb, takes another leap, and moves W/SW by another 55 kms, to 8.6N and 81.5E.It is just 50 kms east of Trincomalee, Sri Lanka. Later, continuing its track thru Sri Lanka, the system should strike Indian mainland at current strength in the region targeted by vagaries . But peak winds constant at 35 knots (in the West and Southern sector).....
Vagaries track projection has remained unchanged since the last 

AS-2, in the last 6 hrs, has remained stationary at 6.5N and 71E, at remained at 1008 mb...almost in the same position since Sunday mid-day report.

Chennai will get windy weather and frequent rains on Tuesday Gusty NE winds at 40 kmph. Rain amount 30 mms.(average)
Wednesday will be overcast with frequent thundershowers. Rain amount around 45-50 mms.

Mumbai: Tuesday 30th and Wednesday 31st: Light  clouding will keep day warm at 34c. Nights will be around 23c.
Thursday 1st Nov: cloudy with stuffy nights. Light rains expected on Thursday night and/or Friday. 

Posted @ 8.00 pm IST:

In the last 6 hrs (since vagaries' report), BB-10, a deep depression, strengthened to 996 mb, takes a  comparatively  "bigger" leap, and moves W/SW by another 110 kms, to 8.6N and 82E.But peak winds constant at 35 knots (in the West and Southern sector).....

AS-2, in the last 6 hrs, has moved 6.5N and 71E, that is in a Westerly direction and remained at 1008 mb...

Next update: 11.30 pm IST

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Posted @ 2 pm IST Monday..Position:

BB-10 almost stationary, having moved just about 10 kms due west..South and SW quadrant show maximum winds at 35 knots, while west and North show 25-30 knots...clouding thick in West and South sectors...
AS-2 also stationary and at 68.9E, shows no signs of deepening yet..


Posted @ 9.00 am Monday:
BB-10, depression, and getting deep, is now at 9.6N   83.7E, almost stationary since our last report ( Yesterday, below), as a depression at 1000 mb and getting deep. Just East off the Northern tip of Sri Lanka, it will move along the projected track and hit Central regions of Coastal TN, near,  Sivaganga and Ramanathpuram,  as a deep Depression.  
Coastal regions of TN will be gusty with 35-40 knts winds and Chennai as expected strong NE winds. 
Peak of the precipitation will be in central TN with some places getting upto 12-15 cms and maybe 18 cms in the odd place.

AS-2, still at 1008 mb, at 6.2N and 68.9E, has moved west, also as expected, and should deepen a bit initially.

BTW, the trough from O-3 is expected to push deep into Central India by tomorrow.

Next Update by 2 pm IST Monday...

Sunday Mid-Day (28th October):

BB-10, now as a depression is currently at 10N and 84E, with a core pressure of 1002 mb. 
As the system is just South of the favourable ridge (mentioned earlier), it will track West, and due to adjacent wind shear at 20 knts, it will deepen more, and develop a stronger wind force in the Northern semi circle. This semi circle will have winds upto 30 knts, and Chennai will get gusty NE winds of the same speed from Sunday night  itself.

BB-10 will move into central coastal TN around Monday night, with centre at Nagapattinum/Karaikal. Heavy falls in Puddukotai and Thanjavur districts. But, rainfall will be increasing throughout the TN regions from Sunday evening, with heavier falls in the Northern coastal regions.
After crossing land, the system weakens.

AS-2 , is now located as a low at 6.5N and 72E, with core pressure at 1006 mb.

I personally make it that this system faces multiple problems in its life time !  System faces  stiff resistance from O-3, which is moving Eastwards, will not allow it to track Northwards, but force an Easterly track. 
On the other hand, being located far too Southwards, a superb feeding in the Southern semi circle from Southerly winds at 30 knts, will strengthen the Southern quadrant with thick clouding. Problems for the poor guy !!
I feel, it will be forced to track NW  for sometime, and strengthen upto mid Arabian Sea location, and then dissipate in the sea.

From Monday, as BB-10 moves inland. 
See vagaries Chart map for easy reference. 

We, see as a result, Easterly winds along South-East coast of India, to the Mah regions, and South-Westerly wind from AS-2 over the Western side. This creates a line of dis-continuity in the Peninsula and initiates clouding and an unstable atmosphere.

Chennai: Increasing rains from Sunday. Rainfall will be around 30-35 mms on Monday (till Tuesday 8.30 am) with gusty NE winds. Rainfall upto 40 mms continues into Tuesday as well. Decreasing amounts from Wednesday.

Good Showers for Bangalore from Tuesday into Wednesday.

Mumbai: Dry weather till end of October. But temperatures will be on the higher side till end of this month.(and even after in first week).

Arabian Sea UAC descends to 925 hp level, and remains embedded in the axis, which is running along the 7N line. 

UAC around 7N and 72E, and will descend to sea level as a low within 24 hrs. As a system (AS-2), it will move W/NW, along the 10N , due to a ridge, which will form from the system.

Now, the only factor which may alter the course could be O-3, as i see it coinciding with the timing of AS-2. What we must remember is that AS-2 is far too much in the South at this stage.

BB-10, now at 11.7N and 88.7E, has moved West, deepened to 1004 mb. Will move west, as it will be steered by ridge in the Northern Bay. As projected, the high pressure has kept it South. 

We will keep a vigil on the WD (O-3) , though i feel WD will be over India after BB-10 has moved inland. 

WD may not spoil the precipitation over TN.

More tonite, with Chennai forecast...

BB-10 situation on Friday evening, 26th October:

BB-10 in the Bay, having tracked West from yesterday's report, is now situated at 10N and 92.5 E. Core pressure at 1004 mb, and 15 knts winds, without any firm circulation.

BB-10 is now deepening with favourable conditions and SST at 30c, will continue west tracking. The ridge from South West Bengal running thru Bangladesh, will keep the track in the Westward direction. 

Now, as we have discussed possibilities of the tracks before, the WD factor now could be a factor to consider for BB-10. 

A (O-3), WD in the Caspian region may move into Northern Sub-Continent regions. Watching the current charts, the speed of the WD movement seems such that the Northern Pakistan areas may get the WD effect from the 28th October. 

If so, this will restrict BB-10 from tracking North, or even NW, and will contain it within 10N.
Hence, as discussed yesterday, this combination of formations could  favour rains for TN and Southern AP, from Monday, as BB-10 moves towards the east coast,  .

An UAC/Low has formed on the Southern tip of India, at 8N and 72E west of Sri Lanka. As mentioned yesterday, and as of now, i see this tracking  west/North-west,  into the Arabian Sea.