In recent years monsoon onset dates have advanced because of a change in its pattern, said DS Pai, scientist and head of climate research services at IMD Pune. (Satish Bate/HT PHOTO)
In recent years monsoon onset dates have advanced because of a change in its pattern, said DS Pai, scientist and head of climate research services at IMD Pune. (Satish Bate/HT PHOTO)

Monsoon to cover entire country by June 16, a fortnight ahead of schedule

IMD said conditions are also favourable for monsoon onset over some parts of northwest India including Delhi between June 12 and 15
By HT Correspondent, Hindustan Times, New Delhi
UPDATED ON JUN 12, 2021 01:03 AM IST

The South-west monsoon is likely to cover the entire country except south Rajasthan and Kutch region of Gujarat during the next 5-6 days, at least a fortnight ahead of schedule, IMD said in a statement on Friday. Monsoon has advanced into many parts of south Gujarat region, south Madhya Pradesh and Chhattisgarh, and most parts of North Bay of Bengal and most parts of West Bengal, on Friday.

The northern limit of monsoon (NLM) is passing through Diu, Surat, Nandurbar, Raisen, Damoh, Umaria, Pendra Road, Bolangir, Puri, Canning and Malda.

The conditions are favourable for further advance of south-west monsoon into some more parts of Gujarat, Madhya Pradesh, remaining parts Chhattisgarh and Odisha, entire West Bengal, Jharkhand and Bihar, some parts of east Uttar Pradesh and remaining parts of North Bay of Bengal during next 48 hours.

IMD scientists said conditions are also favourable for monsoon onset over some parts of northwest India including Delhi between June 12 and 15 owing to rain and thunderstorms expected in the region. Monsoon normally makes its onset over Delhi around June 27.

A low pressure area has developed over northwest Bay of Bengal and adjoining Odisha and Gangetic West Bengal coasts with the associated cyclonic circulation extending upto mid-tropospheric levels. It is likely to become more marked during the next 24 hours and will move west-northwest across Odisha. Under its influence; widespread rainfall activity with isolated to scattered heavy to very heavy falls are very likely over most parts of east India and adjoining Central India from Friday onwards.

“Monsoon has been very active this year right from onset. The westerly and southwesterly winds are very strong over Arabian Sea and now a low pressure area over Bay of Bengal is pulling the monsoon flow. Both branches on the Arabian Sea and Bay of Bengal side are supporting the advancement of monsoon over the country except dry regions of Rajasthan and Kutch,” explained RK Jenamani, senior scientist, national weather forecasting centre.

IMD last year announced new monsoon dates based on onset data from 1961 to 2019, and withdrawal data from 1971 to 2019. Until 2019, the onset and withdrawal dates were determined based on records between 1901 and 1940. As per the old monsoon progress dates, the monsoon would cover the entire country only by July 15.

Extremely heavy rain (≥ 20 cm) is likely over Odisha on Friday; over Chhattisgarh during the weekend; over East Madhya Pradesh on June 13 and 14; over Vidarbha over the weekend. Due to the strengthening of westerly winds along the west coast in association with the low pressure area; widespread rainfall activity with heavy to very heavy rains are likely to continue over coastal & adjoining ghat districts of Maharashtra and coastal Karnataka during June 11 to 15. Isolated heavy rainfall is likely over Kerala and Konkan till June 15.

Due to west-northwest movement of the low-pressure area and its remnant, widespread and heavy rain is very likely over parts of northwest India (excluding Rajasthan) during June 12 to 14. Very heavy rain is also very likely over Uttarakhand on June 12.

It is also expected that the onset of monsoon over some parts of northwest India will happen next week between June 12 and 15. “The low-pressure system will move west-northwestwards and there will be easterly winds in the region. We are expecting widespread rains in Haryana, Uttar Pradesh, Delhi, Punjab etc because of this. Conditions may be favourable for monsoon onset over this region including Delhi during that period,” said Kuldeep Shrivastava, head, regional weather forecasting centre.

Thunderstorms are likely to be especially severe over West Bengal, Sikkim, Odisha, Jharkhand, Bihar, Madhya Pradesh, Chhattisgarh, Uttar Pradesh, Punjab, Haryana, northwest Indian Himalayas and will be accompanied by frequent cloud to ground lightning and strong gusty winds. This may cause injuries leading to casualties to people and animals working outdoors, IMD has warned.

Monsoon’s progress over the entire country has advanced in recent years according to IMD scientists.

“We had issued new monsoon onset and withdrawal dates last year because we noticed that monsoon dates had advanced in some regions and delayed in some regions in recent years due to many factors including global climate change. The thresholds have changed now. For example, the new onset dates are delayed by 3 to 7 days in many parts of central, west and east India because we noticed this delay while the complete coverage of monsoon in the country is advanced.

“This year is exceptional because monsoon has covered parts of central India very early. Monsoon has covered the entire country by June end in the past also but this year its trajectory is exceptional. Monsoon dates have definitely changed in recent decades, its a very dynamic system. Its movement is strongly influenced by low pressure systems forming over Bay of Bengal. I remember a very long time ago the first monsoon low would form over Bay of Bengal around June 15, but now its forming early as you can see,” said M Rajeevan, secretary, ministry of earth sciences.

“Last year also monsoon had covered the entire country by around June 26 so its not rare. The movement of monsoon depends on how early a low pressure system forms. Its active progress will sustain till the low pressure system sustains and then monsoon progress may weaken temporarily. In recent years monsoon onset dates have advanced because of a change in its pattern,” said DS Pai, scientist and head of climate research services at IMD Pune.

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