Conditions have turned favourable for the La Nina weather phenomenon in the Pacific Ocean to start in the next few months, the Climate Prediction Centre of the National Oceanic and Atmospheric Administration of the US has said, which could lead to above average rainfall and floods in India during the monsoon that begins in June.
NOAA issued a La Nina watch last week, saying the phenomenon could form as early as June-August 2024, with higher confidence during the following seasons.
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Experts said the general expectation based on trends during previous La Nina events is that La Nina during monsoon months is likely to cause above-normal rainfall in India, but warned that this also comes with the possibility of excessive flooding in some parts of the country.
In India, an El Nino is associated with a harsher summer and weaker monsoon. La Nina, on the other hand, is associated with a strong monsoon and above average rains and colder winters in the subcontinent.
La Nina generally tends to follow strong El Nino events, as seen in the past few months, which also provides added confidence in the model guidance favoring La Nina, NOAA said.
{{/usCountry}}La Nina generally tends to follow strong El Nino events, as seen in the past few months, which also provides added confidence in the model guidance favoring La Nina, NOAA said.
{{/usCountry}}In summary, a transition from El Nino to ENSO-neutral is likely in the next month (June). La Nina may develop in June-August (49% chance) or July-September (69% chance), according to NOAA projections.
Much of India’s monsoon rains are spread over July and August. Consistent and moderate amounts of rain — as opposed to heavy or very heavy rainfall days — is crucial for a country where nearly half of the farmland lacks irrigation. Good rains can help keep prices of staples such as sugar, pulses, rice and vegetables under control, in turn restraining the sticky inflation problem.
The weather bureau has already forecast above normal monsoon at 106% of the long-period average, a year after this number was below normal at 94%.
The India Meteorological Department’s (IMD) Monsoon Mission Coupled Forecasting System has also indicated the likely development of La Nina conditions during the monsoon season. It has also said that at present, neutral Indian Ocean Dipole (IOD) conditions are prevailing over the Indian Ocean. The latest MMCFS forecast indicates that positive IOD conditions are likely to develop during the monsoon season.
“We’ve seen a quick switch from El Nino to La Nina several times before in our 1950-present record, especially after a strong El Nino. This tendency is one source of confidence in the prediction that La Nina will develop later this year,” NOAA said.
The current El Nino event, which developed in June 2023, was at its strongest between November and January, the World Meteorological Organisation (WMO) said in March. It displayed a peak value of about 2°C above the 1991-2020 average sea surface temperature for the eastern and central tropical Pacific Ocean. This made it one of the five strongest El Nino events ever, though it was weaker than the 1997-98 and 2015-2016 events, the WMO added. The El Nino event was preceded by three consecutive years of La Nina conditions (2020-23) — a rare “triple-dip” phenomenon that had widespread impacts on the ocean and climate across the globe.
DS Pai, head of the climate service division at IMD, said it will take a few months for the SST anomalies to transition to the La Nina threshold of below -0.5°C in the equatorial region of the Pacific Ocean. “With the establishment of La Niña sometime during the monsoon, we can expect flooding rains in parts of the country, including the west coast, the Himalayan foothills, and the core monsoon region in central India,” Pai said. “IMD has already forecast an above-normal monsoon at 106% of the long-period average with a model error of ± 5%.”
Mahesh Palawat, vice president of climate change and meteorology at Skymet Weather, said the forecast of positive IOD conditions, along with the expected transition from El Nino to La Nina, is expected to create conditions for a good monsoon in India. “Heat wave conditions will also be relieved. Due to ongoing western disturbances, we are also not expecting any heat wave conditions over northwest India immediately,” Palawat said.