It is not often one sees Weather Models show heavy rains over many parts of Tamil Nadu & widespread rains across the state. At the cost of repeating us once again, calendar is just for human convenience while nature revolves around its own pace. Similarly the NEM season ending on 31st December is only for administrative convenience and statistical reference though the actual Northeast Monsoon ends many a times before that or extends well into the new year.
More often than not when a classic La Nina forcing happens we see the Northeast Monsoon conditions extend well into the second fortnight of December & First fortnight of January. This year is no exception with models indicating this active spell of rains for many days now. With the mid latitude westerly trough in the mix we could possibly see fairly intense thunderstorms at times due to highly unstable atmospheric conditions.