It may be ironical to talk about Rains when Pongal festival is just around the corner. Before we start calling it “Unseasonal Rains” it is essential to look at the background. When La Nina influence drives the weather dynamics. Of the 5 disturbances that formed after Christmas since 1950 3 of them were when La Nina influence prevailed. The most famous one being the Thane Cyclone during the year 2011. Similarly 5 out of the 12 disturbances that have formed during the month of January happened during La Nina years. 2023 saw a depression form as late as 30th January and impact Sri Lanka.
The larger issue with the “Unseasonal Rains” during Pongal is the impact on the farming community. This is the time when across Tamil Nadu paddy crops are ready for harvest. Between 2nd fortnight of Margazhi and the 1st fortnight of Thai bulk of harvesting happens in TN. As we get closer to the harvest window even moderate rains may be counter productive. With mechanised harvesting the order of the day wet fields become unfavourable. Additionally if the rains are accompanied by strong winds Lodging could also add to the damage.
Ensemble weather models continue to indicate starting from the next 24 hours over the next few days Tamil Nadu may come under rains. A cyclonic circulation now over South Bay is expected to drift gradually west across Sri Lanka. As it moves west most coastal areas may start seeing moderate rains from 11th. Models indicate places like Chennai in North TN may see rains for a couple of days. Delta districts and South TN may possibly come under rains for more days.
The ensemble rainfall estimate chart indicate most places in South TN could see its heaviest rains on 14th or 15th during the next 7 days. This also holds good for some of the interior areas of Tamil Nadu though the expected rainfall quantum is much lower. The movement of the circulation over Comorin Sea is likely to trigger heavy / very heavy rains over the Ghats of South TN around Pongal period. The Ensembles picked up the earlier rainfall event around year end / New year too. During that rainfall event Oothu in Tirunelveli recorded 35 cms between 30th Dec. and 1st January.
As far as rainfall quantum goes it appears North TN may see light / moderate rains on 12th and 13th. Interior areas may see rains on 14th / 15th January while South TN may see rains continue after Pongal too. The threat of rainfall is unlikely to be major for normal day to day activities. But for the farmers, particularly in Delta and South TN it may impact if the crops are ready for harvest. As things stand there is very less chance for any extreme rainfall event over the next few days. But with potential interaction between lower level Easterlies and Mid Level Westerlies there is a chance one or two places may see heavy to very heavy spell of rains based on real time wind pattern.