October 2021 has turned out to be the rainiest for the state of Kerala. Between 01st and 18thOctober, the state has recorded 445mm of rainfall against the normal of 183.5mm. Revised monthly normal of October for the state stands at 303.4mm.
Prior to 2019, the average rainfall was shade lower at 292.3mm. The variability of rainfall is very high in the month of October. During the last decade itself, October remained deficit by more than 50% in 2016 and surplus by a similar margin in 2019.
October Rainfall- Kerala (Surplus/ Deficiency : %)
Southwest Monsoon has withdrawn from most parts of the country. Retreat is considered complete, once the withdrawal line reaches 15°N. Very small portion of Northeast India ( Manipur, Mizoram, Tripura), Odisha and North Interior Karnataka await withdrawal and the same should happen anytime soon by 22nd October.
This milestone, once reached, also clears stage for ushering of Northeast Monsoon. Anticyclonic circulation over the Andaman Sea is expected to shift eastward, facilitating establishment of easterly winds, a pre-requisite for onset of South India Monsoon.
Prior to this change over, another weather feature is appearing in the equatorial region, in the proximity of Sri Lanka and Southwest Bay of Bengal. A cyclonic circulation over Sri Lanka and Comorin region, coupled with an easterly wave will move across Tamil Nadu and Kerala.
Rainfall activity will pick up from 20thOctober onward. Heavy rain and thundershower, with a large spread and varying intensity is expected to lash most parts of the state between 20th-25th October. This spell will also pave the way for onset of northeast monsoon.
Courtesy, heavy rains over the state, all the water bodies are nearly full to the brim. Some of the dams are already in the process of releasing surplus water, through the canals and rivers.
The riparian pockets down the lane will have the risk of water breaching embankments. Ground and sub soil is nearly saturated with the localized flooding and inundation. Any further rains will surely compound the problem and raise the degree of difficulty, for relief operations.