Posted 6th December Night:

# BB-18 showing rapid movement and development. Convective bands have appeared to the North and East of a well formed Low level circulation. Thus developed into a Depression. Cloud banding steadily becoming prominent. Centre of circulation approximately at 9.2N and 91.5E. 
System will track NW. As per indications today, will track towards North A.P.( Vizag) Coast and may cross the coastline by around 10th evening. Cyclone strength possible. 
Seems it will by-pass Chennai ?

Rainfall in Andaman Islands till now from BB-18 as compiled by Pradeep John.

Dense fog likely in Parts of NCR, Uttar Pradesh and Bihar next 3 mornings.


Posted 5th December Monday:

# BB-18, a Well Marked Low, is currently at 5N and 98E. The system tracks W/NW initially, and soon has a potential to develop in favourable conditions.Currently it has an elongated low level circulation, which will concise as it strengthens.
Seems as of now, will track NW till it reached 87E-90E region. 

The strength and exact location of the WD coming in the North regions on the 10th will depend where and how the WD and its associated upper height tilt is located.
As of now, judging the BB-18 and upper level trough in the North West regions of the sub continent, the effect of WD may be possible in Kashmir and H.P. only and in extreme North Pakistan. 


BB-17 has moved into the East Central Arabian Sea area.

Posted 3rd December Saturday:

# BB-18 is still to form. Slow on the schedule mentioned yesterday, There is an UAC over the expected region (of BB-18 formation). UAC will descend to form a Low on 4th around the location 7N and 92E. 
Observing the parameters, and the steering Sub Tropical Ridge, we (today) see the track, as the system on formation, heading towards the A.P. coast. The conditions favour the formation of a Cyclone on approaching the East Coast of India.


BB-17 has emerged in the Arabian Sea. A Low is seen over the Lakshdweep region.An associated UAC also prevails.

Posted Friday Night (2nd December):

# BB-18 (Low) likely to form on 3rd around location 7N and 92E. Initial study of parameters show track as NW towards A.P. coast. Again, synoptic conditions indicate further strengthening and high possibility of Cyclone formation on reaching coast. At present it seems BB-18 will cross coast after about 5 days.
Follow BB-18 on Vagaries...Rare occasion when Vagaries has announced the possibility of Cyclone formation before system is formed.
Next update: Saturday Night (3rd) at 11 pm IST.

BB-17 is now stationed in interior T.N. as a Low. Upper air trough associated with it is tilting towards South West.

Chennai got 39.5 mms and Chennai AP measured 35 mms in 24 hrs as on Friday morning.Vagaries estimate was around 50 mms.
Some Thursday Day temps and Friday morning Lows: Adirampatanma saw a high of 21.5c, and a Low of 18.9c.
Karaikal saw a high of 22.6c and a low of 22c.
Kodaikanal saw a high of 13.4c and low was 10.7c.
Many towns in TN saw a cool day at around 23c, with the range between day and night of around 2c.

Posted Thursday Night ...

True to its expectations, BB-17 is crossing into Tamil Nadu on Thursday night as a Depression.
Vagaries has never mentioned a Cyclone from the start of its tracking BB-17 8 days ago. And also clarified yesterday that IMD and International Models are mentioning a Cyclone. 

Chennai received 30 mms on Thursday in 12 hrs ended 5.30 pm. 50 mms were estimated here in 24 hrs.

BB-17 is a Low level Circulation ( Depression) crossing the TN coast tonite. The estimated winds around the circulation is 30 knts. Vertical shear is not favourable for the circulation.
It is not showing any associated deep convection.

Let us start the chase for BB-18 ...Likely to form around the same location as BB-17. 

BB-18 could be more effective for TN...

Posted Wednesday Night:

BB-17 has been upgraded to Cyclone "Nada" status by IMD and International Weather Models.

As per IMD Bulletin .." The cyclonic storm “Nada” over southwest Bay of Bengal moved northwestwards during past six hours with a speed of about 27 kmph and lay centred at 1730 hrs IST of today, the 30th November, 2016 near Latitude 9.8ºN and Longitude 84.0ºE over southwest Bay of Bengal, about 550 km southeast of Chennai,"

Moving along the Southern Edge of the Sub Tropical Ridge, this "Cyclone" will track towards the Tamil Nadu coast. 

Please not I have put "Cyclone" into inverted commas.Estimated central Pressure is 1000 mb and estimated core winds at 40 knts, 

Heavy showers expected in Chennai from 1st December, amounting to around 50 mms. Rains will decrease to half the amount on 2nd and substantially decrease thereafter.

Posted Tuesday 29th Night:

BB-17 is now a Depression, estimated location on Tuesday night is at 6.5N and 87.1E. No change in track forecast.
Chennai: Squally weather from 30th, with very windy conditions on 1st, winds gusts upto 45-50 kmph. Thunder showers on 1st December.Around 50 mms of precipitation expected.
Bangalore: Showers on 1st December, with cool day at around 24c, Can expect around 25 mms on 1st.

Mumbai: Mumbai skies will get partly cloudy the next 3 days, Wednesday 30th - Friday 2nd December. 
Days, which are quite hot currently at 34-35c, will see a fall to 31/32c levels. But, no appreciable fall seen in the night temperatures.Maybe a marginal rise in the minimum temperatures from Wednesday night.

Pune: Next 3 days will be partly cloudy to cloudy on Thursday. Substantial drop in day temperatures from the 34/35c levels. But rise in night temperatures, maybe by 5c...minimum rising to around 15c from Wednesday night.

Posted 28th November Night:
Initial Gear Up of NEM ...

As mentioned yesterday, BB-17 has formed and is a Well Marked Low in the South -East Bay Region as on Monday evening. System is intensifying fast, and can become a depression by Tuesday Night. 
Tracking NW and heading towards Tamil Nadu Coast as expected.Could cross South of Chennai around 1st. By 3rd, BB-17 ( Weak Low) re-emerges in the Arabian Sea off Kerala Coast.
Squally winds likely along TN coast from 30th, and rains commencing from 1st December.
BB-18 follows soon...

Chennai: Rains expected from 30th evening. Around 55-60 mms from  30th Night-1st Night. Gusty winds and squally weather, with wind speeds peaking around 55-60 kmph on 1st December.
Bangalore: Thursday 1st December, and the city will cool down with heavy showers in most parts. With around 15-20 mms on Thursday, the day's high will be around 25c. Friday 2nd, will be overcast with lesser rains, but cooler day at around 22/23c.

Mahableshwar (Maharashtra) , a hill station at an average height of 4400 feet above sea level, recorded its hottest ever November day at 32c !
Bangalore, the Garden City, also saw a new November record at 33c !
The Day Night range continues in Maharshtra. 
Shivkumar Mogal sends this table of 28th November.

Posted 28th November Night:
Initial Gear Up of NEM ...

As mentioned yesterday, BB-17 has formed and is a Well Marked Low as on Monday evening. System is intensifying fast, and can become a depression by Tuesday Night. 
Tracking NW and heading towards Tamil Nadu Coast as expected.Could cross South of Chennai around 1st. By 3rd, BB-17 ( Weak Low) re-emerges in the Arabian Sea off Kerala Coast.
Squally winds likely along TN coast from 30th, and rains commencing from 1st December.
BB-18 follows soon...

Chennai: Rains expected from 30th evening. Around 55-60 mms from  30th Night-1st Night. Gusty winds and squally weather, with wind speeds peaking around 55-60 kmph on 1st December.
Bangalore: Thursday 1st December, and the city will cool down with heavy showers in most parts. With around 15-20 mms on Thursday, the day's high will be around 25c. Friday 2nd, will be overcast with lesser rains, but cooler day at around 22/23c.

Mahableshwar (Maharashtra) , a hill station at an average height of 4400 feet above sea level, recorded its hottest ever November day at 32c !
Bangalore, the Garden City, also saw a new November record at 33c !
The Day Night range continues in Maharshtra. 
Shivkumar Mogal sends this table of 28th November.

Thirivallur & Puducherry -92%, Kancheepuram -88%, Nammakal -87%, Salem & Vellore -86% and Chennai -83%...to mention a few,a very poor picture is depicted for Tamil Nadu. (Below)

i) After a very Poor November Start for the North East Monsoon, things seem to be looking bright soon.
After the formation of the much awaited trough, On 28th November, low pressure (BB-17) is forming at 5N and 90.5E in the South East Bay.....System will intensify, and track towards the Tamil Nadu coast. The intensified system may cross as a Deep Depression South of Chennai around 1st December.
Squally winds are likely along the T.N. coast from 30th November.
Studying the current possible scenario and BB-17 strength, the estimated rain amounts ( estimated as on 27th November) for Chennai would be around 55-60 mms on 1st, and then reducing to around 15-20 mms on 2nd December. But we will judge and monitor the developments daily.
BB-17 will weaken on crossing, and a weak Low will re-emerge in the Arabian Sea.

Another back to back Low, BB-18, is possibly forming in the same 5N and 90E region around the 3rd of December. Along a trough, the BB- 18 will track almost along the BB-17 track towards TN.


ii) Massive temperature variations were seen in some Maharashtra towns on 26th/27th November...

On 26th November Ahmednagar (Maharashtra) max temp 35.4°C and min temp 6.6°C. So, Temperature difference was 28.8°C.(Ahmednagar record and India range record is 29.2c on 15th December 2003.See here on the page for more variation ranges and Sub Continent record of 29.5c...
on 27th, Mumbai Scruz saw a difference of 19.6c, (high for a coastal city), when the day was 36.2c and night 16.6c. 
Pune saw a range of 22.8c, with 32.1c as the high and 9.3c as the low.