Low pressure area to form in Bay of Bengal next week, to revive monsoon

Vinson Kurian Thiruvananthapuram | Updated on August 13, 2021

Rains to come back to Central, Peninsular India

India Meteorological Department (IMD) has said in an extended outlook that a cyclonic circulation may form over West-Central and adjoining Northwest Bay of Bengal over the next two days likely leading to formation of a low-pressure area over the same region subsequently.

Most numerical models surveyed including IMD-GFS, GEFS, NCUM and NEPS, NCEP-GFS and ECMWF deterministic models indicate the formation of the low-pressure area over West-Central and adjoining Northwest Bay off the North Andhra Pradesh-South Odisha during August 12-18.

Weak monsoon continues

This would likely bring the monsoon back to Central and adjoining Peninsular India which have been waiting for meaningful rains after the monsoon trough over land retreated to the Himalayan foothills. The week ending August 11 was the second consecutive week with a weak monsoon here.

Weekly cumulative rainfall departure for the country as a whole for the week ending on August 11 (Wednesday) is 35 per cent below its long period average (LPA), while the seasonal cumulative rainfall departure (deficiency) during the season so far (June 1 to August 11) is six per cent below the LPA.

The emerging low-pressure area will bring fairly widespread rainfall activity across a rain-scanty Odisha, Coastal Andhra Pradesh, Telangana, Vidarbha, and Chhattisgarh. Isolated heavy falls are forecast to break out over Odisha from Sunday to Wednesday, the IMD said in its outlook.

Rainy second half of month

Isolated heavy falls are also forecast for Coastal Andhra Pradesh from Sunday to Tuesday; over Chhattisgarh from Monday to Wednesday; and over Telangana and Vidarbha on Wednesday. Isolated heavy to very heavy falls too have been predicted over Odisha on Monday.

The IMD also said that the ongoing subdued rainfall conditions may persist over the rest parts of the country during next five days and increase thereafter except Northwest India and Gujarat State.

Rainfall outlook for the subsequent week (August 19-25) also hinted at likely increase in rainfall activity over most parts of the country as compared to the past week. The monsoon trough is expected to revert to its near-normal position during most days of the week.

Monsoon trough to shift

The IMD has therefore forecast fairly widespread to widespread rainfall activity with isolated heavy falls very likely over most parts of South Peninsular and Central India during most of the days. Light/moderate scattered to fairly widespread rainfall is likely over rest of the country except most parts of the hills of Northwest India, plains of West Bengal and the Andaman and Nicobar Islands.

Meanwhile, on Friday morning, the monsoon trough was located to the north of its normal position while the eastern end may shift gradually from Sunday southwards towards the Bay where a cyclonic circulation is expected to form over West-Central and adjoining Northwest Bay.

As mentioned earlier, this may concentrate into a crucial low-pressure area by Tuesday over the same region. Under these conditions, the prevailing subdued rain activity over most parts of Northwest India, adjoining Central and Peninsular India may last with varying intensity until Sunday.

Rain for Peninsular India

The situation will reverse with an increase in rainfall first over East-Central and adjoining Peninsular India from Monday, the IMD said. Ongoing widespread rain with isolated heavy to very heavy falls may persist over Northeast India, plains of West Bengal and Sikkim until Sunday and relent.

Isolated extremely heavy falls are likely over Assam and Meghalaya on Friday and Saturday and over the hills of West Bengal and Sikkim today. Fairly widespread to widespread rainfall with isolated heavy falls may continue over East Uttar Pradesh and Bihar until Saturday.

Published on August 13, 2021

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