IMD forecasts below-normal monsoon this year; why it matters

The country is likely to receive below normal monsoon rainfall this year, the India Meteorological Department (IMD) said on Monday, warning that emerging El Niño conditions could weaken India's main rainy season.

The southwest monsoon, which runs from June to September, is expected to bring about 80 cm of rainfall, lower than the long-period average of 87 cm.

"Quantitatively, the seasonal rainfall over the country as a whole is likely to be 92 per cent of long-period average (LPA) with a model error of +/- 5 per cent," IMD Director General M Mohapatra said.

El Nino factor

• The IMD said El Nino conditions are likely to emerge around June after a gap of three years.
• El Nino, a warming of the equatorial Pacific Ocean, is typically linked to weaker monsoon winds and drier conditions in India.
• The last such event occurred in 2023, with earlier instances in 2015, 2009, and 2002.

Currently, weak La Nina conditions are transitioning to ENSO-neutral conditions over the equatorial Pacific. La Nina usually brings a temporary cooling effect on global average temperatures. Also, climate models show that during the second half of the monsoon season, positive Indian Ocean Dipole (IOD) conditions can develop. 

Regional outlook

• Below normal rainfall is expected over most parts of the country.
• Some regions - including parts of the Northeast, Northwest, and South Peninsular India - may receive normal to above-normal rainfall.

Other climate signals

• Weak La Niña conditions are currently transitioning to neutral conditions in the Pacific.
• Climate models indicate a positive Indian Ocean Dipole (IOD) may develop in the second half of the season.

"Positive IOD leads to more rainfall. So, we expect that this will counter the impact of El Niño during the second half of the monsoon season," Mohapatra said.

He also noted that snow cover in the Northern Hemisphere between January and March was slightly below normal, a factor that has an inverse relationship with India’s monsoon rainfall.

Why it matters

• About 75% of India's annual rainfall comes during the monsoon.
• The season is critical for irrigation, drinking water, and hydropower generation.
• Nearly 64% of the population depends on agriculture, which relies heavily on monsoon rains, as only around 55% of the net sown area is irrigated.

The IMD issues its first monsoon forecast in mid-April and updates it in late May.

Separately, private forecaster Skymet Weather has also projected below-normal rainfall this year. 

Skymet ​said the El Niño ⁠weather pattern ​is set to reduce ​precipitation in the second half of the June–September ​rainy season. Monsoon ​rainfall is expected to be ‌94% ⁠of the long-period average of 868.6 mm for the ​four-month ​period.

(With inputs from PTI)