With 2016 winding down as we are in the last couple of days of the year a COMK analysis on how 2016 is going to be a watershed moment as far as rainfall goes for Tamil Nadu & Pondicherry. The numbers presented here are for the Tamil Nadu & Pondicherry sub division as classified by IMD. The data period pertains to 1871 to 2016 since the time IMD has created a homogeneous rainfall data set for sub divisions.
Overall 2016 is on course to record the poorest annual rainfall since 1876. By the skin of teeth 2016 avoids recording the poorest year since 1871. Less than 10 mm will possibly separate the two years when the year ends finally. In what is something that possibly needs to be studied in depth without any more delay is whether the rainfall pattern is undergoing any change as 3 out of the 15 poorest years have happened in the last 15 years. Whether is this a decadal pattern or a long term rainfall pattern change evolving needs to be studied.
In a case of repeating pattern 1876 and 2016 once again occupy the Top 2 spots for the poorest Northeast Monsoon years since 1871. In a curious case of irony 2015 Northeast Monsoon recorded more than what 2016 recorded annually. If not for the last spell of rains from the Trough of Low during the last few days we could have possibly seen 2016 end up as the poorest Northeast Monsoon in almost 150 years. In the end once again less than 3 mm separate 1876 and 2016. In this context the two cyclones, Nada & Vardah, in December possibly prevented 2016 becoming an even bigger disaster than what is currently happening.
If one were to see how much Northeast Monsoon possibly influences the overall annual rainfall those years that saw a very poor Northeast Monsoon more often than not has lead to a poor year overall. 1876, 2016, 1904 all featuring in the 10 poorest years in both categories while 1892, 1938 & 1974 within the poorest 15 years for annual rainfall while they feature in the 10 poorest Northeast Monsoon years. This possibly confirms the importance of Northeast Monsoon on the overall rainfall prospects for Tamil Nadu & Pondicherry.