Weather Instagram at November 24, 2014 at 06:54PM

Nagercoil - 5:22pm, getting ready for a thunder shower. #weather

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Weather Instagram at November 24, 2014 at 02:30PM

Tirunelveli - 2:20pm, again a fully cloudy day. Light drizzle now and light rain ahead. #weather

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When is the next W.D to affect N,N-W India?? May be on Thursday, 27-Nov ... http://ow.ly/i/7GnvL 

Analysis show a low-level circulation seen over Sea just south of Kanyakumari ... http://ow.ly/i/7Gn96 
There's also another low-level circulation seen over S Bay along 5th parallel !
This is expected to drift West.

4:30pm, More showers popping over S Tamilnadu and T showers seen along N Kerala, S coast Karnataka ... http://ow.ly/i/7Gncz 

Some more detail about present rainfall over Southern districts of Tamilnadu ... http://ow.ly/EJQVP 

Till Tuesday noon... less showers forecast for most of Tamilnadu.
As the next S Bay circulation moves towards coast... Rain is expected to be back over S Tamilnadu on 27-Nov.
After a long gap... showers are expected for N,central coast Tamilnadu and Chennai on 28,29-Nov... http://ow.ly/i/7GnqX 

Southern district rainfall

The sequences of [trough] low seen over northern hemisphere and southern hemisphere is depicted in this chart distinctly. This may be the last sequence of trough during this retreating monsoon season for deep south districts Kumari , Nellai & Thoodi.

The low engulfing the southern tip of Indian main land [i.e Kumari, Nellai and Thoothukudi district] and adjoining coastal areas of neighboring coastal districts is to give light to moderate rainfall.
Flooding in some places is inevitable.

Dundee Sat imagery 23.11.2014 / 09Z

தாமிரபரணியில் வெள்ளம் என்பது நிச்சயம். தினமும் வெள்ள நீர்
[3000 கன அடி ] அளவுக்கு கடலில் சென்று வீணாகும்.
[நன்றி : பொ. ப. து / பொறியாளர் திரு. எஸ் ஜி எம் ]

As of now Tirunelveli district recorded 64cm rainfall against 34 cm Normal and Thoothukudi district  recorded 48 cm against 31cm.Normal. 

Weather Instagram at November 23, 2014 at 12:31PM

Tirunelveli - 12:24pm, sharp showers now over eastern zones of city. More ahead. Flood alert for district. #weather

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Weather Instagram at November 23, 2014 at 09:36AM

Tirunelveli - 9:30am, light drizzle now. More rain ahead before evening. #weather

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Weather Instagram at November 23, 2014 at 07:28AM

Near tirunelveli - 7:20am, wet everywhere after 2 days of rain and more rain ahead today for S Tamilnadu. #weather

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RAINFALL CLASSIFICATIONS IN INDIA

FORECAST CATEGORY [IMD LEGEND]

1. WIDE SPREAD                          (most places)               76 - 100 %

2. FAIRLY WIDE SPREAD           (few many places)        51 - 75%

3. SCATTERED                             (few places)                 26 - 50%

4. ISOLATED                                 (one or two places)     01 - 25%

24 HOURS accumulated rain means rainfall accounted from 0830 hrs IST of today to 0830 hrs IST of tomorrow.  That is rainfall ending at 0830 hrs IST [03Z] of date.
The rainfall is reported in mm correct to first decimal. Standard raingauge in India is Fibre glass reinforced Polyester type raingauge of diameter=159.6mm [collector area =200 sq.cm] with relevant measure glass 20mm

[a] heavy rainfall      ::::::::::::::: Greater than or equal to  65.0 mm

[b] very heavy rainfall :::::::::::Greater than or equal to  125.0 mm

[3] extremely heavy  ::::::::::::: Greater than or equal to  250.0 mm

NHET and rainfall in deep southern districts of TN

DUNDEE SAT IMAGERY 211114 15Z 

Once in few decades the retreating SWM gives copious rainfall in southern most tip of India.  This may be due to WEAK  SWM monsoonal winds prevailing  lower latitude close to Equator. These may be considered as Northern Hemisphere Equatorial troughs [NHET] -a prevailing pattern. Before the onset of SWM these NHET as well as SHET forms on either side of 5 Deg latitude. Similarly when SWM is withdrawing  to lower latitude the same pattern prevails.  

This NHET brought heavy to very heavy rainfall over Kanyakumari, Tirunelveli, thoothukudi districts of TN.  The cloud band below Srilankan deep south is active.