March is not the month one associates with rains particularly over the coastal areas of Tamil Nadu though the places closer to the Western Ghats tend to slowly get into the Veppa Salanam groove due to changing wind conditions as a precursor to seasonal wind change ahead of the Southwest Monsoon Season. But there are occasions when Tamil Nadu records very good rains even during the month of March, including the coastal areas, under favorable conditions.
The biggest factor in this favorable condition has to be La Nina conditions especially when there are signs of devolving La Nina or La Nina starts to slow down towards neutral Enso conditions. 2008 which is the year Tamil Nadu saw rare floods during the month of March on account of a Low Pressure Area, 1984 & 2006 all have one thing in common, negative ENSO conditions that was mostly devolving. For that matter even 2009 which saw a favorable Trough of Low also had supporting Nina conditions.
2022 is heading towards negative neutral conditions with La Nina expected to devolve into Negative neutral conditions during the summer of 2022 so in principle. But devolving La Nina alone does not guarantee heavy rains during March with 1996 a very good example of not so great rains during the first quarter of the calendar year. With a Low Pressure Area expected to form in South Bay closer to the Equatorial waters the chance of 2022 heading in the direction of 1996 may be lower than heading in the direction of 2008 or 2009. Though a Low Pressure Area is expected to form in South Bay there are multiple factors that are making the dynamcis fluid & it is not as straight forward as weather models have been suggesting.
The changing dates in terms of the rainfall event as estimated by some of the models have been going back and forth an indication of narrow window of favorable factors for the rainfall event to happen. ER wave is likely to keep both the circulations on either side of equator connected for the next couple of days which could keep the circulation south of what models estimate as of now. Additionally a potential interaction between Western Disturbance and lower level Easterlies could mean the scenario cannot be Fifty Shades of Grey instead we are going to see either a widespread Rainfall episode due to the Low Pressure Area or we may end up watching the circulation get pushed NE under the influence of the incoming westerly trough. Not to forget a slightly stronger than model estimated scenario would mean a NE recurve under the influence of a Ridge over Indo China Peninsular Region.