Monsoon to arrive in Kerala, parts of Northeast likely by Thursday

Weather scientists said that Cyclone Remal, which ripped through West Bengal and Bangladesh on Sunday, had pulled the monsoonal flow to the Bay of Bengal, which could be one of the reasons for early onset over the north-east.

Kerala has been receiving heavy rains for the past few days resulting in a surplus May rainfall, the weather office data showed. The normal monsoon onset date for Arunachal Pradesh, Tripura, Nagaland, Meghalaya, Mizoram, Manipur, and Assam is 5 June.

“The conditions also continue to become favourable for further advance of Southwest Monsoon into some more parts of South Arabian Sea, remaining parts of Maldives, Comorin, Lakshadweep, southwest and central Bay of Bengal, northeast Bay of Bengal and some parts of Northeastern states during the same period,” the IMD said.

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IOD now neutral, to turn positive in August

The IMD declares onset of monsoon over Kerala if anytime after 10 May over 14 stations there and neighbouring areas receive 2.5 mm or more rainfall for two consecutive days, the Outgoing Longwave Radiation (OLR) is low, and the direction of the winds is south-westerly.

Monsoon is critical for India’s agricultural landscape, with 52 percent of the net cultivated area relying on it. It is also crucial for replenishing reservoirs critical for drinking water, apart from power generation across the country.

June and July are considered the most important monsoon months for agriculture because most of the sowing for the Kharif crop takes place during this period.

El Nino conditions are prevailing at present, and La Nina may set in by August-September, scientists say.

El Nino – the periodic warming of surface waters in the central Pacific Ocean – is associated with weaker monsoon winds and drier conditions in India. La Nina – the antithesis of El Nino- leads to plentiful rainfall during the monsoon season.

The IMD is also anticipating the development of a positive Indian Ocean Dipole (IOD) or cooler-than-normal Indian Ocean in the east compared to the west, which helps bring rain to several states in southern India.

The IOD is currently ‘neutral’ and is expected to turn positive by August.

Another factor is the below-normal snow cover in the northern hemisphere and Eurasia. Historically, there has been an “inverse relationship” between the levels of snow here and the monsoon.

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