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Monsoon near reprise of record-breaking 2019

Vinson Kurian Thiruvananthapuram | Updated on September 30, 2020 Published on September 30, 2020

With a neutral Indian Ocean, a La Nina in the making may have aided it this year

The 2020 monsoon season, that drew formally to a close on Wednesday, will be known best for nearly matching the record-breaking rainfall pattern of 2019, though without the prop of a strong positive Indian Ocean Dipole and the associated effects witnessed last year.

While 2019 saw 110 per cent of the long-period average of rainfall in what has been described as the heaviest monsoon in 25 years, its immediate successor has not lagged too far behind by delivering 109 per cent (final figure awaited) without so much as a prop from the Indian Ocean basin.

The heavy 2019 monsoon rode on the shoulders of one of the strongest Indian Ocean Dipole (IOD) events on show. This year, the Indian Ocean has been neutral; if anything, model forecasts indicate a negative IOD developing, known to suppress a concurrent monsoon.

The only external influence on this year’s monsoon could well have been a La Nina event in the making in the tropical Pacific, which has traditionally been associated with a good monsoon here. A formal La Nina call — declared recently — came in late, but the associated build-up may have helped it.

 

Good rainfall distribution

A major highlight of the 2020 monsoon has been the manner in which the rainfall has come to be distributed evenly across time and space. But there is also no papering over the rainfall deficits in the North-West and the North-East. These abnormalities are built into the planetary weather system.

Central India and the South Peninsula made most gains with not a single State recording a rainfall deficit. In the North-West, Ladakh, Jammu & Kashmir, Himachal Pradesh, Uttarakhand and Delhi bore the brunt of a truant monsoon. In the North-East, Nagaland, Manipur and Mizoram made it into the list.

Low in making

Meanwhile, on the last day of the monsoon on Wednesday, the India Meteorological Department (IMD) predicted the formation of a rain-driving low-pressure area in the Bay of Bengal. This might set a trend for the rest of October, as per the global forecasts that were available on the same day.

While the IMD expects the low to keep East and North-East India wet until at least October 4, global forecasts say rains may scale up over Peninsular India from October 9 and become heavier from October 19, likely indicating the arrival of the North-East monsoon.

Areas coming under the footprint of the rain regime include Andhra Pradesh, Telangana, Maharashtra and the adjoining West Coast down to Coastal Karnataka, as well as most parts of Tamil Nadu and Kerala — though the rainfall may be less intense over the southern parts of these two States.

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Published on September 30, 2020
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