Like Monday, Chennai has experienced a nippy weather in November, the wettest month every year, on several occasions in the past four decades, when the day temperature had dipped below 26 degrees Celsius. Moreover, this is not the first time when the November weather systems fell short of the expectation of heavy rain and missed reaching the Tamil Nadu coast.
On Monday, the weather stations at Nungambakkam and Meenambakkam recorded 24.9 degrees Celsius and 25.6 degrees Celsius respectively, nearly five degrees Celsius lower than the average. For the second consecutive day, the city recorded the below average temperatures on Tuesday, but slightly better than those of Monday. The two weather stations recorded a day temperature of 26.5 degrees Celsius and 27. 3 degrees Celsius respectively.
The sunshine recorder at the Meenambakkam observatory did not record any sunshine hour between 6 a.m. and 6 p.m. on Monday because of the cloudy sky. Bright sunshine was recorded for only half-an-hour till 2.30 p.m. on Tuesday. The intensity of the incoming solar radiation was minimum, leading to no sunshine hours. A cloudy sky, a cooler earth surface and less terrestrial radiation also led to a sudden dip in the day temperature, said B. Amudha, Scientist-E and in-charge, Aerodrome Meteorological Office, Chennai.
Chennai has experienced a winter-like chill weather during November at least once every decade. The day temperature in November had dropped to 23.6 degrees Celsius on November 14, 1985. In November 1987, the city recorded a maximum of 24.9 degrees Celsius.
Typical of northeast monsoon
Y.E.A. Raj, former Deputy Director-General of Meteorology, Chennai, said cold air advection from the northerly direction when the weather system was over the Bay of Bengal was another reason for the dip in temperature. He recalled the torrential rain between November 4 and 14, 1985, when the city recorded 95 cm. It also influenced a long spell of cold weather.
Pointing to the typical characteristics of the Northeast monsoon, he said 12 weather systems, including depressions and cyclones, that had formed over the Bay of Bengal, south of the Chennai latitude, had dissipated without crossing the Tamil Nadu coast between 1981 and 2021.
The weather systems in November 2005 and November 2021 were similar to that of the weakened depression this month. They had formed near the Chennai latitude and missed crossing the coast, he said.