Monsoon onset likely today after slow revival
NEW DELHI: Monsoon revival, after a 10-day long hiatus, has been slow, the India Meteorological Department said on Sunday, with the monsoon onset now likely to be on the afternoon of July 12.
While it has started raining in some parts of the country, particularly in central and peninsualr India, the northern limit of monsoon (NLM) has been in the same position for 22 days, since June 19. The NLM is the northern most limit of monsoon up to which it has advanced on any given day.
On Sunday, NLM continued to pass through Barmer, Bhilwara, Dholpur, Aligarh, Meerut, Ambala and Amritsar.
“Monsoon revival is very slow. While easterly winds did set in over Delhi, clouds did not form until Sunday. The easterly winds bring a moist air parcel but for clouds to form there has to be vertical ascent of this air which did not happen. Also, there was isolated rain in Rajasthan and Punjab but spatial distribution of rain was limited on Saturday. Now it seems like monsoon is likely to make onset on Monday over Delhi,” said RK Jenamani, senior scientist, national
weather forecasting centre. Monsoon rains should have covered the entire country by July 8.
While IMD is expecting good rains in the next two weeks which is likely to cover the rain deficiency, overall July rains are expected to be below normal over several parts of northwest India and some parts of south peninsula, central, east and northeast India.
There is an 8% deficiency in rains with 23% deficiency over northwest India; 6% deficiency over east and northeast India and 9% deficiency over central
India, as on July 7. There is 7% surplus over south peninsula.
Delhi has a large rain deficiency of 64%; Gujarat 47%; Haryana 37%; Punjab 41%; Kerala 39%; Odisha 20%; Manipur 62%; Arunachal Pradesh 23% among others.
The delays this year – which altogether may be one of the latest yet -- have led to a summer of an unusual spell of high-heat, high-humidity conditions across much of north-west India, and has forced farmers to delay planting their crops, which could lead to some impact to the
agriculture sector at a time when Covid-19 has exacted heavy costs on the economy.
“Temperatures have been very high and there is no rain. This is unexpected in July. Diesel consumption has increased to run our pumps which has led to higher costs to farmers. There are power outages too. In some
places, the paddy crop couldn’t sustain so it has to be sown again,” said Harinder Singh Lakhowal, general secretary, Bharatiya Kisan Union.
Several large scale factors are causing the sluggish revival of monsoon, scientists said.
“There are local and global factors which influence the advance of monsoon. While the break monsoon phase was mainly due to the Madden Julian Oscillation being in an unfavourable position which has gradually resolved. The slow revival of monsoon may be due to negative Indian Ocean Dipole in combination with neutral El Niño/ Southern Oscillation conditions,” explained OP Sreejith, head, climate monitoring and prediction group, IMD Pune.
The Indian Ocean Dipole (IOD) is defined by the difference in sea surface temperature between two areas – a western pole in the Arabian Sea (western Indian Ocean) and an eastern pole in the eastern Indian Ocean south of Indonesia according to the Australian Bureau of Meteorology. The IOD affects the climate of Australia and other countries that surround the Indian Ocean Basin, and is a significant contributor to rainfall variability in this region.
“Normally negative IOD with la nina brings good rain. But due to the impact of negative IOD with neutral La Nina we are expecting rains to be below normal in some parts of the country. Overall however rains may be normal over the country during July,” Sreejith said.
The next two weeks will be critical for monsoon. Lower level easterly winds from the Bay of Bengal have further extended northwestwards, reaching up to Delhi, Haryana and east Rajasthan since Saturday. Low level relative humidity has also increased over the region. Hence, the conditions continue to remain favourable for further advance of southwest monsoon over Delhi, remaining parts of west Uttar Pradesh, some more parts of Punjab, Haryana and Rajasthan during next 24 hours. Conditions are also becoming favourable for further advance of southwest Monsoon over remaining parts of the country during the subsequent 48 hours.
Under the influence of these conditions, widespread rainfall is very likely over northwest India during next 4-5 days and isolated heavy rainfall is very likely over Jammu, Kashmir, Ladakh, Gilgit-Baltistan, Muzaffarabad, Himachal Pradesh and Uttarakhand during July 11 to 13; over Punjab, Haryana and West Uttar Pradesh during July 11 to 13; over east Rajasthan during July 11 to 12.
A low pressure area has formed over westcentral and adjoining northwest Bay of Bengal off north Andhra Pradeshsouth Odisha coasts and an east west shear zone is running in middle levels across Central India. Under their influence, widespread rainfall very likely over Central India (Madhya Pradesh, Vidarbha, Chhattisgarh and Odisha) during next 4-5 days and isolated heavy rainfall very likely over West Madhya Pra
desh, Vidarbha and Chhattisgarh on July 11.
Due to strong southwesterly winds from Arabian Sea; enhanced rainfall activity with isolated heavy to very heavy rain is very likely along the west coast and adjoining Peninsular India during next 5 days.