Tuesday, December 01, 2015

Heavy Rains lashed Chennai on Tuesday 1st December.
The Chennai Meenambakkam rain gauge measured 272 mms in 12 hrs ended 8.30 pm IST on Tuesday.
97 mms from 5.30 -8.30 pm, 
69 mms from 2.30-5.30 pm, 
33 mms from 11.30 am-2.30 pm and 
73 mms from 8.30 am-11.30 pm.

The other regions 14 hr amounts ( till 10 .30 pm IST) compiled by Pradeep is given in below:
Katankollathur (near SRM) 431 mms, Kattupakam 400 mms, Chembarabakkam 369 mms, Kolapakkam 281 mms, Chennai (Meena) 272 mms (10 hrs), Chennai (Nunga) 289 mms, Cheyuur 267 mms, Anna Uni 260 mms, Poonamalle 256 mms, Puzhal Agro 255 mms, Taramani 243 mms, Red Hills 213 mms, Madhavaram 192 mms, 

Why and How ? (This is my personal analysis of the event from my experience and not binding ):

Initially there was a divergence tendency in the 200 hp jet streams. Please, I repeat and stress upon the fact (which is hardly ever followed by fresh meteorologists) that one must always pay attention to the upper most jet streams..they are the weather makers. (This explains why in my Sunday post here I had mentioned rains on Monday and "more rains" for Tuesday.) But of course it turned out to be much much more !!

The divergence in the upper jet streams is shown here:

What is divergence ? 
Certain regions of jet streaks are more favourable for rising or sinking air. Where convergence occurs in the upper levels, sinking motion results. Where divergence (evacuation of mass) occurs in the upper levels, rising motion result. Convergence and divergence in a jet streak is caused by an imbalance of forces as a parcel accelerates into a jet streak then decelerates out of the jet streak. Air is less dense at 200 mb.Vorticity at 850 hp levels is also high.

Hence, obviously, air from lower level rises, and rises fast.This causes a UAC Vortex to form at the lower levels. Some charts may depict it as a Low with Localised pressure dropping to 1008 mb:

Hence, without a system, but embedded in a trough, this results in unfounded very heavy and constant rainfall.
Normally, these "Rapid" vorti can vanish in 3/4 hrs, or last till 24 hrs. (Mumbai downpour of 944 mms vortex lasted 10 hrs).

Chennai rains expected to decrease from late night Tuesday/early morning tomorrow, and will be reduced to 40-50 mms on Wednesday.

Pictorial Explanation of Mumbai Vortex of 2005 Record 944 mms.

Torrential Rains Lashing Chennai...Basic and simple explanation will be put up at 11 pm IST

Rain amounts around Chennai  from Pradeep's Tamilnadu weatherman:
in mm (till 6.30 pm from 8.30 am in last 10 hours )
Kattankolathur (near SRM University) - 368
Katupakkam (near SRM University) - 310
Chembarabakkam - 302
Thiruporur (near Kelambakkam) - 281
Cheyyur - 233
Kolapakkam - 216
Palavedu (near Avadi) - 211
Puzhal Agro - 193
Poonamalle - 193
Taramani - 180
Anna University - 177
Chennai AP (Meenambakkam) - 175 (till 5.30 pm)
Avadi - 174
Chennai City (Nungambakkam) - 165
Puzhal - 157
Redhills - 148
Hindustan Unviersity - 139
Madhavaram - 123
Minjur - 104


TAMILNADU STATE - NEM 2015 (1 Oct 2015 to 30 Nov 2015) -:  517.9 mms (+47 %) 
Best performing and highest rainfall district : Kancheepuram -: 1241 mms ( + 144 %) 
Worst performing district : Madurai -: 354 mms (-1 %) 
Lowest rainfall district : Namakkal -: 277 mms (+8 %) 

After a deficient October ,a vigorous NEM during November saw Chennai AP accumulate 118 cms ( +181 %) of rainfall during November 2015 nearing it's all time November monthly rain records.

This Mumbai type monsoon rains triggered unprecedented floods and waterlogging in Chennai .

Chennai Airport has recorded 208 cms of rain from 1 Jan to 1 Dec (till 2.30 pm) 2015 .It's on course to overtake 234 cms of rains recorded at Mumbai (Tulshi) this year , after  a deficient South West monsoon (SWM).

(CLICK AND ENLARGE FOR BETTER VIEW)Tamilnadu and surroundings (rain in mms)

Chennai: Overnight, Nungambakkam measured 39.6 mms and Meenambakkam 64 mms as at 8.30 am Tuesday (Last 24 hrs).
As forcasted (on Sunday post) in Vagaries, Chennai is seeing "More" rains on Tuesday , with Meenambakkam getting 106 mms in 6 hrs from 8.30 am.
With this Chennai AP has received 17 cms of rain in December 2015 ( nearing it's Dec average ).

Sunday, November 29, 2015

Posted Sunday Night:
Mumbai: Sunday 29th: Daytime was again warm and hot at 34.7c at Scruz and 33.7c at Colaba ( we were expecting a rise). 
Monday 30th will be warm in the day, but evening will be breezy with N/NE winds. A nip in the air with temperatures falling to 18/19c at Scruz and 21/22c at Colaba on Monday night/Tuesday morning.
Cooler nights with a drop in temperatures expected in Pune and Nasik on Monday and Tuesday Nights.

Chennai: Cloudy with some showers on Monday 30th. Rain intensity increasing from Monday evening. Frequent showers expected later on Monday and more on Tuesday 1st.. Chances of heavy spells of rains. 

Heavy rains expected in Pudducherry on Tuesday.

Bangalore will see light rains on Monday with a cool day at 23/24c (Maximum). Similar weather on Tuesday. As of now, seems rains can increase on Wednesday.

Moderate showers possible on Monday and Tuesday in Interior TN, Interior and Coastal Karnataka, Goa  and Kerala. A few heavy falls in coastal Karnataka.
Light to moderate showers expected in M.P. and Chattisgarh on 30th and 1st December. 

Karachi is seeing some pleasant weather recently. With lows around 14/15c. Islamabad is hovering around 7c, while Gujrat (PakPunjab) is around 8c in recent nights. 
Due to absence of any system and cooler winds, conditions can continue for another couple of nights. December 1st and 2nd could be colder.

Light rains expected in Muscat Oman on 30th November.

Saturday, November 28, 2015


Outside of the western ghats , the lowest max temps in the state have been recorded at North Konkan (Mumbai Colaba @ 30 c )
At 2.30 pm today : Mumbai Colaba @ 29 c (hum :45 %) , Mumbai SCZ @ 31.8 c ( hum : 35 %)
Vagarians , please explain/comment on the below mentioned Vagaries of the Weather -map is attached below for reference

It's the time of the year ,when normally the temperature difference between most parts of the Konkan region and those of the Deccan plateau region of the state should be around 5 c on an average.

??But the temperatures have mostly been uniform throughout the state during the past 24 hrs..??

Sample this (28 Nov 2015) --> 
Average temp : Konkan region around 26-27 c and the Deccan plateau region around 25-28 c ..

Konkan region - Mumbai SCZ : 32.8 c / 19.2 c (average 26 c )

Deccan Plateau Region -
Madhya Maharashtra - Pune : 31 / 18.7  (average 24.9 c )
                                     Solapur : 35.5 / 20.2  (average 27.9 c )

Marathwada - Aurangabad : 32.4 / 18.2  (average 25.3 c )

Vidarbha - Nagpur : 32.1 / 17.3  (average 24.7 c )

Sample this for comparison with same day last year (28 Nov 2014) -->
Average temp : Konkan region around 26-27 c and the Deccan plateau region around 21-22 c ..

Konkan region - Mumbai SCZ : 34.8  / 18.7 (average 26.8 c )

Deccan Plateau Region - 
Madhya Maharashtra -Pune : 30.5 / 11.8 (average 21.2 c)
                                    Solapur : 30.7 / 14.5 (average 22.6 c)

Marathwada - Aurangabad : 31.5 / 14.2 (average 21.9 c)

Vidarbha - Nagpur : 31.6  / 13.1 (average 22.4 c)



Friday, November 27, 2015

Mumbai Forecast for 2 days on Mumbai Page..and Mumbai Weather Last 30 days Variations

Sub Continent..Some Rains in Central India and Southern Most Peninsula.