Sept rainfall brings deficiency down to 4%

NEW DELHI: Following rains through September, which has been the most active monsoon month this year, India’s monsoon rain deficiency has reduced from 9% to at the end of August to 4% on Sunday, according to data by India Meteorological Department (IMD).

With this, monsoon has now entered the “normal” category which is 104% to 96% of the long period average, even as more rain is expected till the end of September, according to IMD’s extended range forecast.

But monsoon rains have been extremely skewed this year with 9.6% excess at the end of June; 6.8% deficiency in July; 24% deficiency in July and 28.7% excess in September till Sunday. Instead of July and August which are active monsoon months, September has been the most active monsoon month this year.

According to north Indian Ocean’s extended range outlook, another cyclonic circulation is likely to form over east-central Bay of Bengal around September 23-24 with a near similar pattern of movement as the one that is presently over Madhya Pradesh. This is also expected to bring widespread rains over central and parts of northwest India.

“The monsoon trough is very active right from the northern parts of the country to the western Pacific. The favourable position of Madden-Julian Oscillation (MJO) is supporting convective activity. Though a cyclonic circulation is weaker in intensity than a low pressure system it is likely to bring rain over many parts of the country till end of the month,” said Sunitha Devi, in-charge of cyclones at IMD.

The MJO is an eastward moving disturbance of clouds, rainfall, winds, and pressure that traverses the planet in the tropics and returns to its initial starting point in 30 to 60 days, on average according to National Oceanic and Atmospheric Administration. The MJO’s location and amplitude strongly modulates the intensity of tropical convection and features like low pressure systems over the north Indian Ocean.

The monsoon situation changed so abruptly in September that districts that were “severely” and “extremely” dry as per IMD’s drought monitoring from June to August have switched to “mildly dry” now as per standard precipitation index. SPI is an index used for drought monitoring and is negative for drought, and positive for wet conditions.

For the period June to August 2021, 129 districts are in moder

ately/ severely/ extremely dry condition or moderately/ severely arid condition, and 43 districts are in dry condition in all the three drought indices monitored by IMD.

These 43 districts are under severe water-stressed conditions till the end of August 2021. The maximum number of districts in dry/arid condition were in Gujarat, which are now in wet condition after widespread and heavy rain in September.

Almost all of northeast India and Jammu and Kashmir and Himachal Pradesh continue to be dry.

“There is a sudden revival in dry states which is good because there were drought conditions in Gujarat and parts of Odisha. This will help in groundwater recharge ahead of winter crops,” said Pulak Guhathakurta, head, Climate Research Division, IMD Pune.

“Power of the #monsoon! Rainfall deficit end of August (left) turning to rainfall surplus in mid-September (16th, right). Red colors showing drought and green wet areas! Entire scenario changed due to rainfall in a few days! Regions faces both drought and wet extremes!!” tweeted Vimal Mishra , associate professor, civil engineering and earth sciences at IIT Gandhinagar with maps of soil moisture.

Normally 5 to 6 depressions form during the monsoon season which enhances rain in the core monsoon zone when they travel in the west-northwest direction.

But the first depression of this monsoon formed in September which was followed by a lowpressure system and two cyclonic circulations while another is expected next week.

“A cyclonic circulation has formed yesterday which will travel and bring rain. Another is expected to form next week. There is likely to be active monsoon conditions till end of month. This is mainly because of the location of MJO and active northwest Pacific. The remnants of systems forming in the Pacific also help in development of low is pressure areas and cyclonic circulations over Bay of Bengal. We had forecast this early this month,” explained M Mohapatra, director general, IMD.

Monsoon withdrawal from northwest India is already delayed by three days. IMD’s extended range forecast indicates widespread rainfall till October 7.