Currently, the sea surface temperature conditions over equatorial Pacific suggest moderate La Nina conditions, says IMD
New Delhi: In what could augur a normal southwest monsoon for the country, Indian scientists have identified early signals of moderate La Nina conditions.
Based on its monsoon mission climate forecast system (MMCFS) the India Meteorological Department (IMD) said on Wednesday, “Currently, the sea surface temperature conditions over equatorial Pacific suggest moderate La Nina conditions."
To be sure, the IMD has not made any inferences on the impact of this weather phenomenon on this year’s monsoon.
La Nina is associated with the cooling of the eastern equatorial Pacific Ocean which favourably impacts the four-month long (June to September) south-west monsoon in India, critical to the rain-fed farming season which begins in June. The latest forecast indicates that La Nina conditions are likely to be moderate till spring (May-end) and are likely to start weakening thereafter, IMD said.
The United States’ National Oceanic and Atmospheric Administration (NOAA) in its advisory in early February also stated that La Nina was evident during January in the pattern of below-average sea surface temperatures (SST) across the central and eastern equatorial Pacific Ocean and the overall systems remain consistent with La Nina.
“We do not know how La Nina evolves, but if it continues, it will be favourable for the Indian monsoon," said R. Krishnan, senior scientist at the Pune-based Indian Institute of Tropical Meteorology (IITM), an autonomous body under the earth sciences ministry. He added that if La Nina weakens in the next few months, then the effect on the monsoon may be neutral.
“Even if La Nina weakens, it is sure that El Nino (which negatively effects monsoon) will not immediately develop and it will take several months," Krishnan said.
The MMFCS model developed by IITM has been used to prepare monsoon forecasts since 2012. During the 2018 pre-monsoon season warmer than normal temperatures are likely in all meteorological subdivisions, IMD said, adding, average temperatures over many of the subdivisions from the north-west to central India are likely to be above normal by more than 1 degree Celsius.
On the summer temperature forecast the IMD said that normal to above-normal heat wave conditions are likely over the core heat wave zone in India, spanning 17 states—from Punjab in the north-west to coastal Andhra Pradesh in the south.
Last year too, IMD had forecast hotter than normal summer months but a comparison shows that more states will see an intense summer this year with average temperatures rising above normal by more than a degree.
“The number of heat waves moving will be more... the coming summer will be warmer compared to last year," said M. Mohapatra, scientist at IMD, Delhi, adding, “the rise in temperature will be more for north-western part of the country."
Overall the temperature anomaly patterns shows an increase in the magnitude of anomalies from south-eastern to north-western India, implying temperature rise is likely to be more in the north than in the southern parts of India.