Southwest monsoon set to retreat from northwest India, heavy rains expected in some areas

The southwest monsoon, which has been significantly surplus over the region this year, is expected to commence its withdrawal from northwest India from September 15. The monsoon has devastated many parts of Punjab and Himachal Pradesh, witnessing unprecedented inflow into some dams and heavy flooding in certain low-lying areas downstream.

The combined seasonal precipitation in the northwest part of the country is about 35 per cent above the long-period average (LPA). From June 1 to September 10, the region received 720 mm of rain compared to the LPA of 534.2 mm for this period. For the country as a whole, the monsoon has been seven percent above LPA so far, according to the India Meteorological Department (IMD).

Across India

While Punjab, Haryana, and Himachal Pradesh received rains that have been well above normal, four states have experienced deficient monsoon this year. Meghalaya tops the list with a deficit of 45 per cent, followed by Arunachal Pradesh with 41 per cent, Assam with 33 percent, and Bihar with 32 per cent. Seven other states and union territories, including Kerala, Lakshadweep, Uttar Pradesh, Chhattisgarh, Odisha, Sikkim, and Manipur, received rains below the LPA but within the parameter of ‘normal’. Deviation up to 20 per cent on either side of the LPA is considered normal.

Punjab

Punjab has received 616.8 mm of rain compared to the LPA of 408.0 mm for this period, which is 51 per cent above normal. Tarn Taran has been the wettest district with a surplus of 166 per cent, followed by Gurdaspur with 101 per cent and Barnala with 97 per cent.

Haryana

In Haryana, the monsoon has been above normal by 42 per cent this year. The state has received 564.7 mm of rain compared to the LPA of 398.8 mm. Fatehabad has been the wettest district with a surplus of 144 per cent, followed by Mahendragarh with 122 per cent and Kurukshetra with 103 per cent.

Himachal Pradesh

Himachal Pradesh has received 971.0 mm of rain against the LPA of 682.4 mm for this period, which is 42 per cent above normal. The wettest districts in the state are Kullu with a surplus of 113 per cent, followed by Shimla with 107 per cent and Solan with 73 per cent.

The next two weeks

The monsoon starts its retreat from parts of western Rajasthan, which is also the last area to be covered during its onset. This year will see the earliest start of withdrawal since 2015, when the withdrawal began on September 4. The monsoon normally begins withdrawing around September 17 and completely withdraws from the region around September 25, and from the country by October 15.

According to forecasts issued by IMD, light to moderate rain is expected in some parts of Himachal Pradesh, while isolated to scattered rainfall is likely over parts of Punjab and Haryana during the next two weeks.

Impact of El Nino and La Nina

IMD has predicted that neutral El Niño conditions are currently prevailing over the equatorial Pacific region and are likely to persist throughout the monsoon season. El Niño significantly impacts India’s monsoon by weakening it, leading to reduced rainfall. Neutral El Niño conditions imply negligible impact. However, IMD has cautioned that there is an increased likelihood of La Niña conditions developing during the post-monsoon season, which could bring more rain and lower temperatures.