“The country can expect good monsoon rainfall during the southwest monsoon season this year.
This region has been seeing a declining trend in monsoon rainfall in the last few years.
El Nino is associated with suppressed rainfall during the Indian monsoon, while La Nina is known to help rainfall activity.
Closer to the onset of the southwest monsoon season, El Nino Southern Oscillation (ENSO) neutral conditions are likely to establish,” Mohapatra said.
The Indian Ocean Dipole — which is the Indian Ocean counterpart of El Nino — is in its neutral phase at present.
INDIA IS likely to receive “above normal” rainfall this monsoon, the India Meteorological Department (IMD) said in its first long-range forecast for the season on Monday. The country as a whole is expected to get 106 per cent of the long period average (LPA) rainfall, it said.
Importantly, nearly the entire country, except some pockets in the northwest, east and northeast, was likely to get good rainfall, the IMD said.
This is the first time in a decade that the IMD has predicted “above normal” rainfall at the first stage itself, nearly 45 days ahead of the beginning of the four-month monsoon season. It is usually more conservative with its predictions in the first stage.
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India, as a whole, normally receives 870 mm of rainfall during the monsoon season. This is referred to as LPA, or “normal” (currently, the average of 1971-2020 period). According to the IMD, rainfall between 96 per cent and 104 per cent of this 50-year average is considered “normal”; less than 90 per cent is considered “deficient”; 90-95 per cent is “below normal”; and 105-110 per cent is “above normal”.
“The country can expect good monsoon rainfall during the southwest monsoon season this year. The seasonal rainfall will be 106 per cent of the LPA,” said Mrutyunjay Mohapatra, IMD Director General.
Comparative quantitative rainfall (in per cent) predicted during first stage LRF and realised seasonal rainfall Comparative quantitative rainfall (in per cent) predicted during first stage LRF and realised seasonal rainfall
Last year, the IMD had predicted 96 per cent rainfall in the first stage forecast. The actual rainfall at the end of the season was 94 per cent of the LPA.
Rains during the June-September monsoon season accounts for 75 per cent of India’s annual rainfall.
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This year, multiple indicators were favouring “above normal” rainfall, Mohapatra said. Primary among these was the transition of the weakening El Nino in the Pacific Ocean into a neutral condition ahead of the monsoon onset, and the likely emergence of La Nina towards the latter half of the season.
Explained Below normal in N-E again Northeast India is again expected to get below normal rainfall. This region has been seeing a declining trend in monsoon rainfall in the last few years.
The alternating phases of El Nino and La Nina in the equatorial Pacific Ocean, off the coast of South America, that correspond to the abnormal warming and cooling of the sea surface in that area, strongly influences global weather patterns, including the Indian monsoon. El Nino is associated with suppressed rainfall during the Indian monsoon, while La Nina is known to help rainfall activity.
“The ongoing El Nino event is weakening. But it continues to remain in the ‘moderate’ category. Closer to the onset of the southwest monsoon season, El Nino Southern Oscillation (ENSO) neutral conditions are likely to establish,” Mohapatra said.
“Thereafter, La Nina conditions are expected to emerge during the second-half of the monsoon season, which could bring higher-than-normal rainfall over the country,” he said.
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The IMD said that in the 22 years since 1951 when La Nina conditions prevailed, monsoon rainfall was normal or above normal for 20 years — it was below normal in 1974 and 2000. There were nine years when La Nina conditions were preceded by El Nino conditions, like this year, and rainfall was on the positive side in all those years, Mohapatra said.
“But there are many other ocean-atmospheric dynamic factors which affect the rainfall during the monsoon season apart from La Nina, which we do not have good knowledge of yet,” M Ravichandran, Secretary, Ministry of Earth Sciences, said.
The Indian Ocean Dipole — which is the Indian Ocean counterpart of El Nino — is in its neutral phase at present. But the Met department said that the positive phase of the IOD is most likely to emerge during the coming months.
“During the start of the monsoon season, positive IOD conditions would emerge. Positive phase of the IOD is good for rainfall over India,” Mohapatra said.
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Another positive factor that could favour the monsoon this year is the below average snow cover along Eurasia and northern hemisphere during December-March.
Asked about the probability of pre-monsoon showers during the upcoming seven-phase elections, which will be the second longest in India’s history, Mohapatra said that May will see thunderstorms across northeast and eastern India, especially over Bihar, Jharkhand, Odisha and West Bengal.
“With respect to elections, we are providing all information including climatological and forecast information to the Election Commission,” he said.
