Why India is likely to receive below-normal rainfall in July

India is likely to receive below-normal rainfall in July due to a combination of unfavourable weather patterns, the emergence of El Nino conditions and the absence of key rain-bearing systems, according to the India Meteorological Department (IMD).

The weather department said on Tuesday that the country is expected to receive 94 per cent of the long-period average (LPA) rainfall during the month. The LPA rainfall over India in July, based on the 1971-2020 period, is about 280.4 mm.

In a statement, Dr Mrutyunjay Mohapatra, director general of meteorology at the IMD, said, “During July, below-normal rainfall is likely across most parts of the country except some areas of northwest and northeast India, east-central India and the eastern peninsular region, where normal to above-normal rainfall is likely.”

The IMD said some regions of northwest and northeast India, east-central India and the eastern peninsular region are likely to receive normal to above-normal rainfall.

LPA refers to the rainfall recorded over a particular region for a given period, such as a month or a season, averaged over a long period, typically 30 to 50 years.

The forecast follows a particularly dry June, when India recorded a rainfall deficit of about 40 per cent. Central India was the worst affected, with a deficit of 50.4 per cent.

The country received 99.5 mm of rainfall during the month, making it the fifth-lowest June rainfall since 1901.

According to Mohapatra, five major factors contributed to the weak monsoon performance.

The first was an unfavourable phase of the Madden-Julian Oscillation (MJO), a moving system of wind, cloud and pressure that brings rainfall as it travels around the equator. During a favourable phase, the MJO generates more clouds over southern India, which are then carried northwards by monsoon winds, leading to enhanced rainfall.

The second factor was the absence of low-pressure systems (LPSs) during June.

LPSs are areas where atmospheric pressure is lower than in surrounding regions. They draw in moisture-laden winds, help trigger rainfall and support the advance of the monsoon inland.

Third, most typhoon systems that formed during June recurved towards the North-Northwest direction, resulting in subdued low-pressure activity over the Indian Ocean region.

The fourth factor was the emergence of El Nino conditions this month, which negatively affected rainfall activity.

El Nino is one of the three phases of the El Nino Southern Oscillation (ENSO), a climate phenomenon characterised by changes in sea temperatures across the central and eastern tropical Pacific Ocean, along with associated atmospheric fluctuations.

While El Nino is generally linked to weaker monsoon rainfall in India and a warming effect globally, its opposite phase, La Nina, usually contributes to increased rainfall and a cooling effect.

ENSO also has a neutral phase. The Indian Ocean Dipole (IOD) is currently neutral and therefore cannot offset the negative impact of El Nino. Positive IOD conditions typically result in higher rainfall.

On the progress of the southwest monsoon, Mohapatra said conditions are favourable for further advancement into the remaining parts of Uttarakhand, Himachal Pradesh and Ladakh, as well as more areas of Gujarat, Madhya Pradesh and Uttar Pradesh during the next two to three days.

During the same period, the monsoon is also expected to cover the whole of Daman and Diu, Jammu and Kashmir, most parts of Haryana, Chandigarh, Delhi and Punjab, and some regions of Rajasthan.

The IMD has also forecast above-normal temperatures across much of the country in July.

Maximum temperatures are expected to remain above normal over most parts of India, except for a few isolated areas in West Central India, where normal to below-normal maximum temperatures are likely.

“Meanwhile, the minimum temperatures are also expected to be above normal over most regions of the country, except some isolated pockets of Central and Northeast India, where normal minimum temperatures are likely,” the IMD said.

(With inputs from agencies)