The Northeast Monsoon just set in over Chennai on 28th Oct and it quickly responded with first heavy downpour inundating many areas. The rains commenced late in the night and continued till morning to record 133.4mm till 8.30 AM at Nungambakkam. Airport observatory Meenambakkam measured 57.8mm during this period. While Nungambakkam with 310mm rainfall in October so far has nearly reached its monthly normal of 316mm, Meenambakkam is just about halfway through with 154mm.
There is a precedence for Chennai to have heavy rainfall spell in excess of 100mm within days of onset of Northeast Monsoon albeit with few exceptions. Last 6 years the onset of monsoon has been getting delayed beyond 25th Oct with the exception of 2019 which witnessed early onset on 16 Oct. In the year 2016 & 2018, state of TamilNadu recorded a large deficiency of 62% and 44% respectively.
The current spell is just confined to Chennai and suburbs and isolated elsewhere. Pamban has recorded 87mm and Tuticorin 10mm in the last 24 hours. The intensity of rainfall is going to become light now and remain so for the next 4-5 days. The next spell is expected from 04th November onward.