Southeast India, especially Tamil Nadu and Puducherry experienced unprecedented rainfall activity during November and early December 2015 leading to devastating flood over Tamil Nadu. The city of Chennai, home to nine million people, was worst affected.
For the month of November 2015, Chennai has reported 1,024 mm (40.31 inches) of rain, more than 300 percent of the normal rainfall that is expected for the entire month, according to the Indian Meteorological Department (IMD). December also continued this wet pattern as more than 300 mm (12 inches) of rain fell in Chennai on the first day of the month. This is the wettest December day in more than 100 years of records in Chennai. (IMD report from 2 Dec)
The northeast monsoon season of October to December is the chief rainy season for Tamil Nadu and Puducherry. It is also the chief cyclone season over the North Indian Ocean and hence, low pressure systems forming over the Bay of Bengal and moving westwards contribute significantly towards the rainfall. According to the India Meteorological Department (Report), during November, three large-scale weather systems affected Tamil Nadu and Puducherry causing extensive rainfall activity over the region:
- Deep Depression over Bay of Bengal (08-10 November 2015)
- Well marked Low pressure area over SouthWest Bay of Bengal (12-18 November 2015)
- Low (28 November-04 December 2015).
In its forecast outlook for the 2015 Northeast Monsoon season (October to December) rainfall over the South Peninsula, IMD had predicted above normal rainfall – in excess of 111% of the long period average. IMD factored the influence of the ongoing strong El Nino into its forecast.
A similar weather pattern in November 1997 resulted in more than 760 mm (30 inches) in Chennai but still fell well short of the recent torrential rainfall.
This most recent rainfall has resulted in closure of Chennai's international airport until at least December 6, with disruption of all other forms of transportation. The Rajali naval air station at Arakkonam, 70 km west of Chennai, is functioning as a makeshift airport. Many offices, schools and colleges have been shut due to heavy rains during the past week.
The National Disaster Response Force, the Indian armed forces and emergency workers are busy in rescue work moving thousands of residents from their homes in the worst-hit suburbs to temples, schools and wedding halls. The government has set up 97 relief camps, which are currently providing food and shelter to an estimated 62,000 people.
Indian Prime Minister Narendra Modi visited the region on Thursday 3 December and said he was "pained" by the devastation he witnessed from the air and on the ground. He pledged $290 million in relief funds. India’s Home Minister, Rajnath Singh, told parliament: “Chennai has become a small island. This is unprecedented.”