AdvertisementOn Monday, the IMD said that ENSO neutral conditions would emerge in June and during July – September, ENSO would transition into La Nina.
” Even though there are multiple other factors, like the monsoon low pressure systems and depression, which affect the monsoon rainfall, La Nina is one of the major factors.
This year, due to La Nina conditions, there could be more rainfall during August and September,” said Mrutyunjay Mohapatra, director general, IMD.
According to the IMD, south peninsular and central India is expected to receive ‘above’ normal rainfall, northwest India would receive normal rainfall whereas east and northeast India is expected to receive below average rainfall during the June – September period.
La Nina conditions enhance the ocean heat content in the North Indian Ocean comprising the Bay of Bengal and the Arabian Sea.
The ocean temperatures along the central and equatorial Pacific Ocean were cooling off and neutral El Nino Southern Oscillation (ENSO) conditions are set to emerge anytime soon, the India Meteorological Department (IMD) said.
ENSO is a naturally occurring climate phenomena resulting from ocean-atmosphere interactions. They impact sea surface temperatures along the central and eastern tropical Pacific Ocean.
ENSO has three phases : warm conditions referring to El Nino, neutral and cool conditions referring to La Nina. ENSO affects the global weather and triggers extreme weather in the form of rainfall, heat and coldwaves.
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On Monday, the IMD said that ENSO neutral conditions would emerge in June and during July – September, ENSO would transition into La Nina.
With the southwest monsoon onset over Kerala expected anytime now, marking the commencement of the four-month long chief rainy season, the development of La Nina in the coming months has raised hopes for a good season ahead this year.
” Even though there are multiple other factors, like the monsoon low pressure systems and depression, which affect the monsoon rainfall, La Nina is one of the major factors. In a La Nina year, one could expect above normal rainfall. This year, due to La Nina conditions, there could be more rainfall during August and September,” said Mrutyunjay Mohapatra, director general, IMD.
According to the IMD, south peninsular and central India is expected to receive ‘above’ normal rainfall, northwest India would receive normal rainfall whereas east and northeast India is expected to receive below average rainfall during the June – September period.
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Explained La Nina’s impact on India Except in east and northeast India, all remaining regions are expected to receive normal or above seasonal rainfall, the IMD said in April. Heavy rains could result in some regions witnessing riverine and urban flooding, mudslides, landslides and cloudbursts.
Climatologically, La Nina is known to favour the Indian monsoons. Except the east and northeast India regions, rainfall over remaining parts of the country, during a La Nina year, ends up either being normal or above.
“La Nina generally supports a stronger monsoon wind flow. A stronger monsoon flow can supply the moisture for the monsoon depressions and bring more rain. However, there is no clear indication on whether the number of monsoon depressions are different during a La Nina year,” said Roxy Mathew Koll, scientist at the Pune-based Indian Institute of Tropical Meteorology.
At the same time, the cyclone potential during La Nina years is higher than normal, hence could act conducive for cyclogenesis. La Nina conditions enhance the ocean heat content in the North Indian Ocean comprising the Bay of Bengal and the Arabian Sea.
” Along with the favorable conditions during a La Nina, the North Indian Ocean temperatures have been increasing at a rapid pace. Many of the extremely severe cyclones (in the past) intensified rapidly in response to warm ocean conditions providing a consistent supply of heat and moisture,” Koll added.
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The recent La Nina event was during 2020 – 2023 dubbed as the longest of this century.
