Southwest monsoon 2021 has typically played truant this year. Though nothing is new about its mischievous character, this season has gone overboard defying assessment and expectation. By virtue of the long span over a period of 4 months (June-September), its undulating conduct is quite reasonable. However, stalling the process of ‘onset’ for a long duration is surely an outlier.
Within 6 days of its mainland arrival, the monsoon reached Mumbai, announcing a resounding onset with extremely heavy rains. In just 24 hours, between 05th and 06th June, it covered entire Northeast India and also reached Sikkim and Sub Himalayan West Bengal. It took merely 48 hours, from 11th-13th June, to advance over West Bengal, Odisha, Bihar, Jharkhand, Chhattisgarh, East Madhya Pradesh, and East Uttar Pradesh. Southwest monsoon covered 80% of the area in just 10days, nearly going supersonic and rarely observed in the recent past. This sprint of the monsoon led to speculation that the current possibly will reach national capital Delhi well before time on 15th June, a repeat of 2008 and 2013.
Between 11th and 13th June, the monsoon took a leap to scan a large area of Bihar, Jharkhand, East Uttar Pradesh, Uttarakhand, Himachal Pradesh, Ladakh, Jammu & Kashmir and also brushed northern parts of Haryana and Punjab along the foothills. This is one of the earliest arrival on record over the hilly states and foothills of north India. From hereon, the further movement got stalled, and advance over Delhi was held in abeyance. Also, the monsoon is not likely to stream in over the rest of Punjab, Haryana, and the whole of Rajasthan for over 10 days from now and extendable to 2 weeks. Some incremental advance of monsoon is quite likely over some parts of west Uttar Pradesh, Madhya Pradesh, and Gujarat. Further, it will fall short of Punjab, Haryana, and Rajasthan.
Typical meteorological conditions and environmental factors are impeding the rapid or even normal pace of monsoon :
- Presence of anticyclone over the Himalayan region and foothill in the higher atmospheric levels (9 km and above) is pushing strong southwesterly winds over North India. These steering winds are blocking the movement of the weather system persisting over Uttar Pradesh for the last few days. These winds play a dominant role and control the movement of monsoon systems. This pattern is easing out after 26th June and till then movement of driving systems will remain blocked. A fresh low pressure will be needed around that time to push the monsoon further.
- Northwesterly winds are prevailing over North India even in the lower levels (below 7000’). These need to be replaced with monsoon easterlies for a sizeable duration.
- Monsoon trough extending from Ganganagar (Rajasthan) to the Bay of Bengal need to be established for speedy movement of monsoon systems. This is an essential feature for bringing monsoon current over North India.
- Many times, the monsoon systems lose strength before reaching the last posts of Haryana, Punjab, and Rajasthan. Coincidentally presence of an active western disturbance moving across the region and working in tandem with the weakened weather system can hasten the progress of the monsoon stream over North India.
It appears that the monsoon is going to have a slow march for the next few days. Even the capital city Delhi may overshoot its normal date of 27th June with the monsoon. There could be further slippages for its arrival over Punjab, Haryana, and Rajasthan. In any case, the normal date of arrival over most parts of Punjab and Haryana is around 30th June or later. The last post of Rajasthan gets covered by 07th July. Hopefully, the monsoon conditions will revive around the normal dates to shun any disappointing or apprehensive moments.