Two more rain systems brewing in the Bay

Vinson Kurian Updated on September 22, 2021

Columbia varsity’s IRI, too, sets up a La Nina watch

The Bay of Bengal could throw up two more rain-generating circulations before the month is out; of which the first is already under watch for development by the India Meteorological Department (IMD).

The second may materialise off the Tamil Nadu coast by the month-end, as per its projections.


Rain deficit for the country as a whole has already shrunk to three per cent, which means the monsoon has entered ‘normal’ territory (96-104 per cent of long-period average). This could well be sustained till end of the season since incoming systems would bring even more rain inland.

The first system is expected to develop over East-Central and adjoining North-East Bay by Saturday and move towards the Odisha coast during subsequent two days.

Under its influence, a fresh spell of heavy rainfall is likely to be triggered over Odisha and adjoining areas from Sunday, the IMD said.

Pacific conditions

As already reported, weakening of the negative Indian Ocean Dipole in the country’s backyard combined with a likely return to La Nina phase in the Pacific away to the Far-East and an active storm phase in the West Pacific/South China Sea have helped the monsoon cause.

The International Research Institute (IRI) for Climate and Society at Columbia University became the fourth global agency to set up a La Nina watch on Wednesday.

Most global models surveyed expect the Equatorial Pacific to cool through the autumn and winter, and return to ENSO-neutral levels during in spring and early summer late of next year (2022).

IRI projections suggest that the Equatorial Pacific has more than 60 per cent chance for ‘neutral’ conditions in May-June-July, 2022 (early part of the South-West monsoon); around 20 per cent for La Nina; and around 15 per cent for El Nino, considered a monsoon-killer though with exceptions.

MJO assisting La Nina

The Australian Bureau of Meteorology said late yesterday (Tuesday) that a Madden-Julian Oscillation (MJO) pulse just exiting the Indian Ocean and entering the Maritime Continent (Indonesia et al) will strengthen the trade winds, cool down the waters and expedite the La Nina.

Ongoing typhoon (cyclone) season in the West Pacific has ensured that remnants track westwards and enter the Bay of Bengal to set up cyclonic circulations as is being witnessed even now.

Of these typhoons, Chanthu, the first, had gone on to become a Category-5 storm and struck Japan.

Back home, the IMD said on Wednesday that the previous day’s low-pressure area over extreme East India may weaken by Thursday and move as a cyclonic circulation across North Odisha, north Chhattisgarh and north Madhya Pradesh during subsequent 2-3 days accompanied by rains.

IMD rainfall outlook

The IMD has forecast fairly widespread to widespread rainfall with isolated heavy falls are likely over east Rajasthan and east Gujarat until Saturday.

Fairly widespread to widespread rain with isolated heavy falls may lash east Madhya Pradesh, Vidarbha and Chhattisgarh till Friday and reduce in intensity thereafter.

Published on September 22, 2021