The Depression in Bay of Bengal is expected to move in an North-North Westerly direction and move towards Cuddalore region around 21st morning. Wind Shear is so less, it is expected to intensify a lot tomorrow into even Deep Depression and by that time it will be close to land. Not sure if it can become a cyclone or not as it is near the land. The conditions are damn favorable. If it becomes a weak cyclone, then it should not be a surprise too. The Depression is expected to move in West-North Westerly direction which means Northern Areas of the Depression will have clouds, so this time North TN cannot miss this spell.
Heavy to very heavy and also extreme rains
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Cuddalore - Pondy - Villupuram are the hot spot of very very heavy rains while Karaikkal, Thanjavur, Nagai, Ariyalur, Perambalur, Kancheepuram, Tiruvallur, Chennai, Tiruvannamalai will all see heavy rains. Other districts nearby can catch a good spell.
"Surely this spell deserves a Red alert warning for Tamil Nadu particularly for NTN districts" - There is going to be some serious rains to be dumped in the NTN districts.
Chennai - heavy rains can be expected from tonight / 21st morning.
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Moderate Rains to start today with on and off spell and it will turn into heavy spells from 20th Night and 21st morning and again rains will extend 22nd and then from 23rd rains will start to reduce. Make or break rains means, Chennai normally gets 850 mm rainfall during NEM in 3 months. Till date it has got only 225 mm. The next 3 days rains are important. Chennai cant afford to miss this spell. This spell alone cant make lakes around Chennai full. We need atleast one more spell in Chennai after this spell. So if 20th morning rains are less. Dont comment no rains. Peak rains are expected for Chennai only from Night. Yaravathu No rain in Chennai. No rain in Kilpauk. No rain in Santhome Pottenga semma tension ayuduvan!!!!
Rain Water Harvesting
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Dont miss to conserve water from the incoming rains in Chennai through Rain water harvesting. Do clean them and keep it ready.
North Interiors
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Even Dharmapuri, Krishnagiri, Salem, Vellore, Namakkal will all catch atleast one day of rains.
Cyclone Gaja affected areas
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Nagai, Thanjavur,will see heavy rains on 20-21st and among the other Cyclone affected areas Pudukottai and Tiruvarur will see one day of moderate rains.
Winds
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Winds of this system should not be compared with Gaja. This hardly has one day left for crossing the coast. If it manages to remain in open seas it might intensify further. As of now Depression is confirmed and might even become Deep Depression. 50-60 km/hr sustained winds can be expected from this system around North TN districts of Cuddalore, Pondy regions.
Next active spells - Monsoon is not over
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Tamil Nadu till date this NEM has got only 243 mm rains against 305 mm. The next 3 days rains might push TN even into positive territory or close to that figure. MJO will be back in December in our basin and this should trigger some m more major rains for Tamil Nadu. In between some weak spells might happen.
Courtesy - Tamil Nadu Weatherman