INDIA is staring at the driest monsoon season in a decade, with the Met office Friday making a downward revision its earlier forecast and predicting only 90 per cent rain this season.

In April, in its first forecast for this year’s monsoon, India Meteorological Department (IMD) had said the country was likely to get 92 per cent of the long-period average (LPA) rainfall during the four-month season.

The LPA, revised every 10 years, is the average rainfall over the 50-year period 1971-2020, which is considered the baseline, or normal. Its current value is 89 cm for the rainy season — June to September — across the country as a whole.

The latest forecast is the lowest by IMD in the last 20 years.

If this holds, India could be in for the driest rainy season since 2015, when the overall seasonal rainfall happened to  be 86 per cent of the LPA.

In the last two decades, there have been only two other occasions — 2009 and 2014, apart from 2015 — when seasonal monsoon rains have remained below 90 per cent of LPA. This year looks all set to join that group.

IMD’s updated forecast Friday showed there was a 60 per cent chance that the seasonal rainfall would be below 90 per cent of LPA.

The IMD did not say what prompted the downward revision in its forecast. However, more recent assessments of the emerging El Nino in the equatorial Pacific Ocean, and of the Indian Ocean Dipole could be the possible reasons.

Since its previous forecast in April, more information about the emerging El Nino has become clear. El Nino, a largescale ocean-atmospheric interaction in the equatorial Pacific Ocean that influences weather patterns worldwide, is known to suppress rainfall over the Indian region.

There are predictions that this year’s El Nino, which could persist well into the next year, could develop into one of the strongest ever.

The possibility of the emergence of an El Nino has been known for the last few months, but forecasts made for this phenomenon during March and April usually suffer from a greater degree of uncertainty, something that is referred to as spring barrier.

The information coming about El Nino now is considered more accurate and robust. Recent forecasts suggest the formation of a strong El Nino.

“With these limitations (spring barrier) and the understanding back then regarding the intensity of the emerging El Niño, we made calculations of the monsoon forecast to be around 92 per cent in April. However, we have downgraded the forecast keeping in view two things — emergence of moderate-strong El Niño earlier in the season than anticipated. In addition, the transition of the Indian Ocean Dipole from neutral to positive is expected only during the latter-half of the monsoon season. All put together, we arrive at 90 per cent of LPA this year,” said a senior IMD official.

The Indian Ocean Dipole (IOD) refers to the temperature differential of surface waters between Bay of Bengal and the Arabian Sea side. If the latter is warmer, that is considered a “positive IOD” and heralds a better monsoon that may offset, to some extent, the adverse impact of a strong El Nino.

IMD said Friday the El Nino was expected to be weak in June, moderate in July and August and strong in September. This would mean that most of the monsoon season would pass off when the El Nino phase is weak or moderate. However, its actual impact on the rainfall cannot be quantified.

As for IOD, the IMD’s earlier assessment was that it would transition from a neutral state to positive state during the monsoon season, which could counter some of the effects of the El Nino. But on Friday, the IMD said IOD was likely to remain neutral through the entire monsoon season.

This year, therefore, looks all set to end an unusually good run of monsoon seasons for India.

Five of the last seven years, including the last two years, had produced more than 100 per cent rainfall. The other two years, 2021 and 2023, were also not bad, bringing in 99 and 95 per cent rains respectively.

The monsoon rains account for nearly three-quarters of India’s annual rainfall, and are extremely critical for agriculture, electricity generation, drinking water purposes and industrial use. The rains during this season fill up the reservoirs which serve the water needs of the country through the rest of the year.

While low rainfall is, no doubt, a reason for concern, it might not bring immediate pain. India’s foodgrain stocks are in a comfortable state, following a good harvest last year. The impact of El Nino is likely to be felt only in the second half of the monsoon season, by which time the kharif sowing season should be over. The threat of El Nino is much bigger for the winter rabi crop.

The major reservoirs of the country have sufficient amounts of water right now because of ample rains last year.

However, lack of adequate rains is expected to push temperatures up. IMD said the country was expected to receive less than 92 per cent rains in the month of June. It also said that temperatures in most parts of the country in this month are likely to be above normal.

The number of heatwave days are also expected to be at least 2-3 days longer, particularly in the northwest region comprising western Uttar Pradesh, Punjab, Haryana and Delhi.