Rains expected again in Delta & South TN in next 2 days, All Time January Rains for Tamil Nadu is under threat

Monster in making in Bay, No chance of cyclone crossing Tamil Nadu, but Tamil Nadu chances for Rains depends upon how close it comes before taking north journey. Kerala will get pull effect rains irrespective of where it goes.
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Many of you would have seen news flash, the UAC in Andaman sea which caused massive rains to Banda Aceh in Indonesia has atlast descended from upper level to surface, this means low pressure has formed. I have explained the reasons in common man language, hope you can understand them. Please give a fast read, so u can grasp them.

1 Why Strong Cyclone chances are too high
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This one will intensify into a monster and will become even extremely severe cyclone, if not a Super Cyclone. It has MJO support which has skipped Pacific ocean and has come back to Phase 2/3, further Sea surface temperature (SST) of bay of bengal is boiling hot at 30-31C, monsoon surge bringing in abundant moisture. Total cyclone heat potential is over massive 150 KJ/cm2 near north TN coast. No threat of dry air and no threat of high windshear. There is some moderate shear on the way, but those are offset by other good ingredients of Cyclone.

2. Delay in intensification needed for System to move close to TN coast
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The low pressure in Andaman is expected to move towards Tamil Nadu coast in W-NW direction, here is the key thing to be noted, as long it is weak it will be easilyt pushed near us, but on the way, the SST get 30-31C further monsoon surge meets our low, there is a sudden bloom and the low pressure intensifies fast and takes steering shift. and moves north. Even if intensifies little late, it can come close to our coast and give rains to us. Remember there is 0 chance for cyclone to cross Tamil Nadu coast. In the case of delay in intensification it will come close to TN coast and will move to Andhra on the way it will intensify into monster again. So either bangladesh or andhra, it will be a strong cyclone. If Andhra we will get rains and less chance of heat wave.

3. Chennai Rain Chances ? Lets see how close the cyclone needs to come close to us
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North moving May cyclone and Chennai rainfall. I have compiled the closest the cyclone was from Chennai coast. So, we need cyclone centre to come within less than 220 kms for us to get rains.

1925 Cyclone moved from SE to NW and 218 kms away from Chennai – 100 mm

1952 Cyclone moved SE to NW and 148 kms away from Chennai – 470 mm.

1979 Cyclone moved from SE to NW and 195 kms from Chennai – 140 mm

1990 Cyclone moved from S to N and 172 kms away from Chennai – 410 mm

2010 Laila eye moved from SE to NW and 149 kms away from Chennai – 210 mm

2016 Roanu moved from S – N and 108 kms away from Chennai – 200 mm

4. Other parts of Tamil Nadu
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With Cyclone on other side, there is no chance of direct rains but when the cyclone is nearby we can see intense thunderstorms forming in our state with thunder and lightening which can dump high amount of rainfall in short periods.,

5. Kerala Pull effect rains
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Irrespective of Andhra or Bangladesh, Kerala will be seeing pull effect rains. When ever cyclone is in Bay of Bengal, if will try to pull moisture from the other side, we can good bands of clouds falling over Kerala during this period. So its a win win situation of Kerala irrespective of where cyclone goes, they will get heavy rains. Kanyakumari too often falls in this place, remember Cyclone Roanu, when it went up in 2016, Kanyakumari got massive rains.

6.Threat of heatwaves for TN and Chennai, if cyclone moves directly away from us without giving rains
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If the cyclone moves to Andhra, we wont see much of heat wave, but if the cyclone moves to Bangladesh / Burma without giving rains then Tamil Nadu, Andhra are in for frying as the Cyclone will drag away all moisture away and the land breeze will become strong this means hot winds from north west will be pushed into TN. Further with offshore winds being strong, the sea breeze will struggle to come in and this means prolonged heating.

7.All time Chennai Hottest days ever in May month
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45 C in May 2003 (Cyclone curved to Burma)
44.1 C in May 1998 (Cyclone curved to Burma)
43.6 C in May 1980
43.4 C in May 2002 (Depression to Burma)
43.2 C in May 1976 (Depression to Burma)

8.What does Models say
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Bangla group – ECMWF, GFS, GEM, ICON, IMD, JMA all take the cyclone up north

Andhra group – UKMET (namma famous BBC), BOM, NCMWR and WRF all bring cyclone close to TN and take it to Andhra

Rainfall in Tamil Nadu on 13.05.2020, one of the best days for Coastal belt in May.
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in mm (min 10 mm)

The Upper Air Cyclonic circulation over comorin area and neighbourhood persists and now extends upto 1.5 km above m. s. l.

Thanjavur
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Peravurani- 102
Lower Anaicut – 49
Tiruvidaimarudhur – 42
Kumbakonam – 36
Orathanadu – 21
Aduthurai – 20
Maddukkur – 11
Thiruvaiyaru – 10

Nagapattinam / Myladuthurai
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Tharangambadi – 80
Manalmedu – 34
Myladuthurai- 33
Vedaranyam – 24
Talaignayaru – 18
Nagapattinam – 17
Kollidam – 17
Sirkali – 14
Nagapattinam – 10

Cuddalore
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Bhuvanagiri – 66
Km koil – 62
Lalpet – 60
Chidambaram – 43
Annamalai Nagar – 42
Kothavachery – 20
Kuppanatham – 16
Me.Mathur – 11
Parangipettai – 10

Villupuram
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Manampoondi- 50
Kanjanur- 36
Nemoor – 28
Soorapattu- 24
Villupuram – 21
Olakkur – 10
Anandhapuram – 10
Mugaiyur – 10

Kanyakumari
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Chittar I – 42
Kannimar – 34
Suralacode – 24
Nagercoil – 22
Mylaudy – 22
Pechiparai – 21
Boothapandy – 19
Perunchani – 16
Eraniel – 16
Puthan Dam – 15
Thuckalay – 15
Kuzhithurai – 11
Colachel – 10

Ramanathapuram
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Rameswaram – 40
Theerthandathanam – 31
Mandapam – 24
Thangachimadam – 15

Tiruvarur
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Tiruthuraipoondi -34
Nannilam – 34
Needamangalam – 18
Tiruvarur – 15
Pandavaiyar Head – 10
Valangaiman – 10
Kodavasal – 10

Pudukottai
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Mimisal – 35
Manamelkudi – 29
Pudukkottai – 16
Kattumavudi – 15
Karambakudi – 12
Ayinkudi – 11
Adankottai – 11
Nagudi – 10

Ariyalur
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Tirumanur – 34
Ariyalur – 15
Jayamkondan – 10
Sendurai – 10

Tirunelveli / Thenkasi
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Shencottah – 23
Papanasam- 20
Tenkasi – 18
Servalar – 16

Others
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Karaikkal – 52
Mahabalipuram, Chegalpattu – 29
Periyar, Theni 29
Puthu Vettakudi, Perambalur – 12
Eravangalar Dam, Theni – 10
Upper Bhavani, Nilgiris – 10