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Monsoon to be normal this year, onset and withdrawal dates revised for some cities: IMD

Monsoon to be normal this year, onset and withdrawal dates revised for some cities: IMD

The India Meteorological Department (IMD) said the country would witness a normal monsoon this year in its first long range forecast (LRF). The IMD said the onset of the southwest monsoon, which brings as much as 70 per cent of the country's annual rainfall, over Kerala remains June 1.

In an online briefing, IMD Director General M Mohapatra said the Long Period Average (LPA) of monsoon would be 100 per cent, which falls in the "normal" category. Every year, IMD releases the long range forecast in two stages during April and June.

"In these difficult times due to coronavirus, the good news is that the country will receive normal monsoon. Quantitatively, the rainfall for the country during June to September season is expected to be 100 per cent of the Long Period Average (LPA)," M Rajeevan, secretary of Ministry of Earth Science (MoES), said.

In the latest LRF, IMD officials stated that the the probability for normal monsoon in the upcoming season was 41 per cent, which is a relatively good figure.

Ocean conditions like El Nino Southern Oscillation (ENSO) in the Pacific Ocean is most likely to continue to remain in the neutral phase during most months of June to September period. An active El Nino is not favourable for the Indian summer monsoon, said Rajeevan.

"Along with neutral ENSO, we expect other ocean parameters like the Indian Ocean Dipole (IOD), too, to remain neutral during the monsoon months," said Mohapatra.

Some dynamic models have indicated at La Nina conditions to develop during the second-half of the four month season, which is expected to contribute towards normal rainfall this year. La Nina is the opposite ocean condition to that of El Nino and it favours the Indian summer monsoon.

The IMD has, however, revised the normal onset and withdrawal dates for the monsoon in some parts of the country from this year after studying the monsoon onset and withdrawal pattern during 1961 -2019. The monsoon onset and withdrawal dates over some cities located in the Western, Central India and and North India have been revised.

From this year, the delay in the onset of monsoon will be effective over Maharashtra, Gujarat, Madhya Pradesh, Chattisgarh, Telangana, Andhra Pradesh, Odisha, Jharkhand, Bihar and some parts of Uttar Pradesh. This delay can range anywhere between three to seven days in comparison to the existing normal dates.

Contrarily, the monsoon arrival dates over extreme northwestern parts of the country stands preponed. This year onward, the revised date will be July 8 instead of July 15 over parts of Rajasthan.

The cities where the onset dates stand revised are Chennai (June 4), Hyderabad (June 8), Pune (June 10), Mumbai (June 11), Ahmednagar ( June 12), Puri (June 13) , Surat (June 19), Nagpur (June 15), Raipur (June 16) , Ahmedabad (June 21 ), Kolkata (June 11), Bhuj (June 30), Bhopal (June 22), Varanasi (June 20), Imphal ( June 5), Tripura (June 5), Jaipur ( July 1) , Lucknow (June 23 ) , Delhi ( 27 June ) and Chandigarh (June 26).

However, the onset dates over Thrivuvanathapuram (June 1), Panjim (June 7) and Gangtok (June 10) shall continue to remain the same.

As for the withdrawal date is concerned, Rajeevan said, " There are appreciable changes in the monsoon withdrawal dates observed over the Northwest and Central regions. This variation has been observed by 7 to 14 days later, from the existing dates," said Rajeevan.

The four-month southwest monsoon season, which ends on September 30, takes about a month and half after onset on the Kerala coast to cover the entire country. It takes about a month, beginning from the northwestern parts of the country on September 1, to withdraw completely.

(INputs and image from theindianexpress.com)

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