El Nino, the Pacific Ocean event has a strong bearing on climatic conditions of India. The El Nino and La Nina events tend to develop during the period April-June and reach their maximum strength between Oct-Feb. Typically, they persist for 9-12 months and occasionally get prolonged to even 2 years or more. The current El Nino event commenced in April, after the collapse of triple dip La Nina and is nearly peaking, right now. It may start diluting before the spring season 2024 of Northern Hemisphere.
El Nino is known for corrupting the Indian Summer Monsoon, popularly termed as southwest monsoon season. The season just gone by finished ‘below normal’ and averted a possible drought : courtesy strong positive IOD in the Indian Ocean. However, the impact of El Nino is not harsh for the northeast monsoon over South Peninsula. Though, the rainfall distribution may not be equitable across all 5 sub divisions of northeast monsoon, but it is generally pleasing for the critical pockets of Tamil Nadu and Kerala. Similar trend is seen this season, as well.
Capital city of Tamil Nadu, Chennai heavily depends on northeast monsoon rainfall. Rains of this season become more crucial because the city lies in the rain shadow area during the southwest monsoon. The impact of El Nino saves the grace for city and suburbs. More than half of the districts of Tamil Nadu have recorded normal or above normal seasonal rainfall, including excess in few of them. The interiors of the state like Erode, Karur, Madurai, Thanjavur are still deficit. The capital city Chennai has recorded 1079.2mm rainfall against the normal of 743.5mm, between 01st Oct and 13 Dec 2023, an excess of 45%. Courtesy cyclone Michaung, the city was adversely impacted for few days, resulting deluge over large areas.
South Interior Karnataka has disproportionate distribution in the north and south region. Southern pockets including Bengaluru Urban, Mysore, Mandya, Kolar have near normal rainfall. However, the region has been generally warmer than normal. The tech city Bengaluru, otherwise known to be slightly cool during Nov-Dec, has remained warmer than average. Monsoon showers have been rather sparse in December and practically no rain for the last about 10 days or so. Accordingly, the mercury levels have risen and both, maximum and minimum temperatures have stayed higher than normal by a sufficient margin.
The city, as such, has warmed a bit over the last 2 decades. Based on long period data between 1971-2000, the normal minimum temperature of the city was 16°C and 15.3°C in December and January, respectively. However, these averages have risen now to 16.4°C and 16.1°C for December and January, respectively. The actual average minimum temperature for the city between 01st and 14th December stands at 19.7°C, way above the tolerance levels. Observatory at Bengaluru city has recorded minimum temperature in excess of 20°C on 06 days, so far in December and the highest being 21.4°C on 09th Dec 2023. The El Nino seem to have warming effect on the city, during otherwise pleasantly cold month of December. If at all, only light sprinkle and that too for short duration, is expected for the city and suburbs during next seven days. No significant change is likely in the temperature profile during this period.