No sleep, so this update at 3.00 am. So forgive for the typos and language.
As winds converge around the low pressure the Veppa Salanam (Heat based or Sun based Convective) rains in Tamil Nadu will reduce. Once the low becomes Cyclone it will tightly wrap up the clouds around it. Hence, convergence will happen at sea around the low pressure are. If lucky some intense inflow bands or pull effect will fall over TN. The lucky places will get intense Thunderstorms.
Note 1: Remember, in June – September, we can see the wind flow from South West in Bay of Bengal and it is very very very rare for Tamil Nadu to get cyclones or direct rains from low pressure. I can remember 1991 and 1996 rains in June with direct rains from low in Bay. Because the cyclone will always dragged up with the flow of monsoon winds and Cylcone / Monsoon Depression during June-September form north of Tamil Nadu cant move south against the SW winds.
Note 2: Before low forms there will be widespread thunderstorms rains in TN and after low forming the rains will be isolated at select locations in TN. Hence, Namakkum Bay low pressure kum entha linkum illa. And for thunderstorms to happen in Chennai, it must be a hot day with sun sizzling followed by rains at evening. If not in Chennai atleast at Vellore-Nagari belt there should be good heat for lifting air particles. The storms can form in Vellore – Nagari belt and then can start moving towards Chennai at night.
Tight agreement on the landfall area around Odisha – West Bengal coast on 26th May. This wont be as strong as Amphan or Tauktae or Fani but will make as a strong cyclone with around 120 km/hr sustained winds at West Bengal / Odisha Coast on 26th May.
Pull effect Rains to Kerala and Kanyakumari
This cyclone Yaas will not have any direct impact to Tamil Nadu except Kanyakumari will get pull effect rains as it activates the arabian sea monsoon winds from 25th. South TN will get spill over from west and so will some western districts. Heavy Rains – Kerala will also have heavy rains particularly in south Kerala for next 5-6 days from 25th may. Trivandrum, Kollam and Kanyakumari has chance of heavy rains on some days between 25-31st May.
Rise in Temperature for SAP and NTN
Temperature in north TN (Tiruvallur To Thanjavur) and north coastal TN like Chennai, Cuddalore, Pondy, South AP like Nellore will increase to 39-41 (+ or – 1 or 2) for 5-6 days with strong North westerlies.