Over the last few days as the winds changed to Easterlies coastal Tamil Nadu has been receiving early morning rains. The remnant moisture from the morning rains in coastal Tamil Nadu develop into thunderstorms over interior areas. The Northeast Monsoon has got off to a very good start with 38% above average as on date. Thunderstorms over the interiors have driven NEM performance so far. Coastal Tamil Nadu has so far been receiving scattered rains primarily created by weak Easterlies.
Things are falling in place a strong monsoon onset is on the cards for Coastal TN. Peninsular India is likely to be under the influence of a train of disturbances over the next few days. The first of the disturbance is already over the Arabian sea in the form of a WML. The well marked low will become a depression in the next couple of days. There is a slight chance it could also become a cyclone as it heads closer to Arabian Peninsula. The one to watch out for is the 2nd disturbance, a pair of cyclonic circulations, over South Bay. While the 1st of the twin is off Sri Lanka / South TN coast, the 2nd one is likely to develop tomorrow. It is essential to point out Northeast Monsoon onset is declared by IMD based on fulfilment of predetermined criteria.
Upon merging there is a very good chance this could become a Low Pressure Area off Coastal Tamil Nadu. Models indicate this disturbance to move towards North TN / South AP coast early next week. This could also intensify into a depression when it comes closer to North TN coast. This could potentially bring the perfect platform for Northeast Monsoon onset early next week. Starting from tomorrow increasing spells of rains during late night / morning hours likely over the coastal areas. From Sunday the spells are likely to become heavier as well.
Meanwhile starting from today / tomorrow Chennai can expect Northeast Monsoon like rains to increase. The intensity of rains are expected to increase gradually from tomorrow. Monday / Tuesday may be the first widespread heavy rains for the city and suburbs. More on this as things evolve. As explained in our NEM Outlook this year a more pronounced WNW / NW track is likely by disturbances which could impact Coastal TN.
One important consideration we need to keep in mind in all this is moisture recirculation. With three different circulations present coastal Tamil Nadu and Coastal AP may see lot of moisture recirculated. This could potentially trigger very heavy to extremely heavy rains over parts of North TN / South AP early next week. As things stand the stretch between Pondicherry to Nellore will be under watch for this potential rainfall impact. Sea temperatures off the TN coast remain very warm which will potentially enhance rainfall event. A cloud burst type of rainfall event in North Coastal TN / South coastal AP cannot be ruled out.