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The North-East monsoon is expected to arrive over the South-East Peninsula around October 26 (Tuesday next). The India Meteorological Department (IMD) indicates that enabling conditions may evolve over the Bay of Bengal at that time.
The onset may have been delayed by three to four days dates beyond the revised October 22 timeline, mainly because the preceding South-West monsoon chose to extend its stay over the mainland.
Easterly wave to bring rain for South
Simultaneous processes
The withdrawal of the South-West monsoon and the arrival of the monsoon in reverse (retreating monsoon over monsoon in reverse) happen simultaneously in the normal course, which is indicated this year too.
Earlier on Wednesday, the IMD limited an ‘orange alert’ for heavy rainfall to three districts in Kerala, giving the vulnerable midlands and foothills a much-needed breather from continued severe weather.
Water levels in major reservoirs at Idukki and Idamalayar have receded after a few shutters were opened yesterday (Tuesday), inflows reducing to a trickle as the weather cleared in the catchment areas overnight on Wednesday.
Flood-ravaged Kerala needs to brace for N-E monsoon now
Gradual build-up of NE monsoon
The short-term outlook from the IMD indicated a slow and gradual build-up of seasonal easterly to north-easterly winds across the Bay of Bengal over the next two days, likely setting off rain-friendly easterly waves.
The US Climate Prediction Centre sees ‘muted’ activity along the Tamil Nadu coast during the week ending October 26 even as upstream West Pacific/South China Sea will stay active watched by a La Niña in the Equatorial Pacific.
US agency forecasts
In its latest update, the International Research Institute for Climate and Society at Columbia University said that a La Niña advisory had been issued for the Equatorial Pacific marked by a consistent cooling trend in the ocean water temperatures.
There is an enhanced 87 per cent probability of a La Niña being triggered in October and sustaining till December, with model predictions indicating that these conditions may persist into the Northern Hemisphere spring during January-March, 2022.
Stormy South China Sea
This translates into a see-sawing warming trend in the West Pacific in typical sea and changes in associated atmospheric weather conditions, sustaining stormy conditions in adjoining the South China Sea with cascading impact on the Bay of Bengal.
The Asia-Pacific Climate Centre based in Busan, South Korea, has said that there is a 90 per cent chance of weak La Niña conditions persisting from November 2021 to January 2022 before these conditions weaken into the spring.
South Korean model outlook
Significantly, the South Korean agency has predicted above-normal rainfall for South Peninsular India from November to January; and average rainfall for Central and adjoining East India, including Gujarat and southern parts of Rajasthan. North and North-West India may witness below-average rainfall.
Meanwhile, the IMD has predicted a fresh spell of the easterly wave, which will likely cause reasonably fairly widespread to widespread rainfall with isolated heavy falls over Kerala, Mahe, Tamil Nadu, Puducherry and Karaikal until Saturday.
Similar conditions are forecast for coastal Karnataka from Thursday to Saturday and south interior Karnataka from Wednesday to Saturday. Isolated very heavy falls are likely over Kerala, Mahe and Tamil Nadu, Puducherry and Karaikal today (Wednesday) and Thursday.
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