In a couple of days time many parts of Peninsular India will celebrate their annual harvest festival Pongal / Sankranthi. While Lohri / Magh Bigu / Poush Sankranthi may not be the traditional harvest festivals of the regions they are also celebrated to herald a change in season. In a way it is apt we are getting ready to bid adieu to Northeast Monsoon and herald the short winter season for most parts of Tamil Nadu. While up North Lohiri is celebrated as a mark of peak winter season coming to an end. This also coincides with Chilla-i-Kalan the harshest period of winter in Kashmir. But for most of Tamil Nadu, particularly the coastal belt, night time temperatures drop only when the Easterlies weaken and bring dry weather along with clear night time skies.
The overall atmospheric conditions indicate things look favourable for Northeast Monsoon to withdraw though MJO continues to be present in the Indian Ocean and adjoining Maritime Continent region. MJO completed its global circuit in late December and started to move across Indian Ocean coinciding with the last rainfall event over Tamil Nadu. On the face of it one may think MJO played a predominant role in enhancing the rainfall event but the current conditions indicate it is not MJO that was driver of the rains but a Tropical and Sub tropical interaction that enhanced the rainfall over the region. With the tropical and sub tropical interaction completed the convection over Indian Ocean has stayed along the Equatorial waters.
Night time temperatures are expected to gradually reduce from now on over the interior areas of Tamil Nadu with early next promising to be the first cold spell of the season. It is important to point out during El Nino periods winters over the Indian Sub Continent are mostly sub par on account of not only the overall ocean warmth prevailing but also frequent Western Disturbances that bring about alternating episodes cold / warm conditions. Starting from the eve of Pongal we can expect a substantial reduction in temperatures over most parts of the state with 18th night expected to be the coolest night in this spell of active winter conditions.
In the meanwhile overall dry weather is expected to prevail over most parts of Peninsular India for the next week to 10 days with easterlies remaining weak and mostly dry continental winds from North prevailing at the lower troposphere.