El Nino impact on monsoon already here, says Met dept

PUNE: Evolving El Nino conditions have begun to impact the rainfall in the second half of the monsoon, India Meteorological Department’s (IMD) said.

El Niño-Southern

Oscilla

tion (ENSO) is an irregularly periodical variation inwinds and sea surface temperatures over the tropical eastern

Pacific Ocean

.El Nino, the warming phase, impacts India's southwest monsoon.

The met department’s El Nino-La Nina forecast had earlier indicated that El Nino conditions are likely to form only after the monsoon.

The probability forecast for El Nino conditions were pegged at over 80% during September-October-November, October-November-December and November-December-January seasons.

Currently, neutral El Nino conditions may change to weak El Nino conditions after the monsoon, according to D S Pai, head of the climate prediction in the climate research division of IMD, Pune.

“Despite a forecast of El Nino developing in the subsequent months, rainfall over the country has been normal so far. However, the evolving El Nino conditions are beginning to impact the rainfall in the second half of the season. This trend may continue into September. Overall, deficiency in the rainfall over northeast India will continue,” Pai said.

The impact, however, may not be as it was during previous El Nino years. “The intraseasonal variability, particularly in the formation of low pressure systems, has affected rainfall distribution over the country so far. It will be so in September too. Though it is early, winter and the 2019 summer in India may have higher than normal temperatures due to El Nino,” he added.

An El Nino event expected during the subsequent months will be the first after 2015-16. Last year, ENSO (the whole cycle of warming and cooling) neutral conditions persisted over the equatorial Pacific Ocean till October 2017.

From November to March 2018, La Nina conditions prevailed. Since April this year, La Nina conditions turned into ENSO neutral conditions and remained so in July.

The monsoon is weaker than normal during the warm phase of ENSO (El Nino) while stronger than normal during the cold phase of the ENSO (La Nina). The intensity decides the amount of the impact.

Past rainfall trends have shown there is stronger inverse relationship between El Nino and rainfall during the latter half of the monsoon season, particularly September rainfall.


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