Monsoon likely to be ‘normal’ at 98% of long period average: IMD
Monsoon in 2021 is likely to be “normal” at around 98% of the long period average (LPA), India Meteorological Department (IMD) said in its long-range forecast on Friday.
“We have good news to share. After two years of above average rain, we are likely to receive normal monsoon rain this year,” said M Rajeevan, secretary, ministry of earth sciences (MoES). The LPA is the average rainfall recorded during 1961 to 2010 which is 88cm. IMD considers rainfall between 96% to 104% of LPA to be in “normal” range.
The 2020 and 2019 monsoon was “above normal” at 110% and 109% of LPA respectively. During 1996, 1997 and 1998, monsoon was normal for three consecutive years at 103.4%; 102.2% and 104% respectively.
La Niña conditions, which started in 2020, have started weakening, Rajeevan said. “La Niña conditions are likely to prevail only till May so we will transition to ENSO neutral conditions during monsoon. There is very little chance of El Niño conditions developing during monsoon months. There is a very small probability of Indian Ocean Dipole (IOD) negative condition developing during monsoon. So these conditions are likely to lead to a normal monsoon this year,” Rajeevan explained.
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El Niño and the Southern Oscillation (ENSO) is a periodic fluctuation in sea surface temperature and the air pressure of the overlying atmosphere across the equatorial Pacific Ocean according to the National Oceanic and Atmospheric Administration (NOAA).
ENSO has a major influence on weather and climate patterns and leads to heavy rains, floods and drought. El Niño has a warming influence on global temperatures, whilst La Niña has the opposite effect. In India for example, El Niño is associated with drought or weak monsoon while La Niña is associated with strong monsoon and above average rain and colder winters.
IOD is characterised by warmer sea surface temperature in the equatorial Indian Ocean; positive IOD conditions are usually associated with normal or above normal monsoon.
A large part of east and northeast India including Jharkhand, Odisha, Bihar and the northeastern states are likely to record below normal rains this year according to IMD’s analysis.
Monsoon is likely to be “normal” or “above normal” for the third consecutive year, according to private weather forecasting company Skymet Weather’s preliminary monsoon forecast for 2021. The forecast said monsoon rain from June to September is likely to be 103% of the long period average of 880.6mm.
“The onset month of June and the withdrawal phase of September is assuring good countrywide rainfall distribution,” Skymet Weather said in a statement on Tuesday. In June, July and August, rainfall is likely to be “normal” with higher probability of “above normal” rain in September according to the forecast.