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Informist, Friday, Nov. 28, 2025

 

MUMBAI – The latest assessments of the El Nino Southern Oscillation indicate that a La Nina event is underway, the Australian Bureau of Meteorology said in its fortnightly report released Thursday. Clear signs in both the tropical Pacific Ocean and the atmosphere are coupled, reinforcing and sustaining the La Nina pattern, the bureau said. The bureau predicts tropical Pacific temperatures are likely to remain at La Nina levels till early 2026 before returning to neutral, which is consistent with most international models it has assessed.

 

The tropical Pacific Ocean parameters have been consistent with La Nina conditions since early October, the bureau said. As of Sunday, the El Nino-Southern Oscillation Index was (-)0.93 degrees Celsius. Ocean surface temperatures in the tropical Pacific between (-)0.80 degrees Celsius and 0.80 degrees Celsius are considered to be neutral conditions, while sustained values below (-)0.8 degrees Celsius for at least three months are considered indicative of a La Nina event. Values of the index have been fluctuating around the La Nina threshold since mid-to-late September, the bureau said. 

 

Atmospheric indicators such as trade winds, pressure, and cloud patterns over the equatorial Pacific also show consistent signs of La Nina. As of Sunday, the 30-day Southern Oscillation Index rose to 16.1, while the 90-day Southern Oscillation is 8.5. Sustained 90-day Southern Oscillation values above 7.0 are indicative of a La Nina event. Trade winds and cloud patterns have been indicative of La Nina since at least mid-to-late September, the bureau said.

 

The Southern Oscillation Index tracks the atmospheric part of the El Nino–Southern Oscillation, while the Oceanic Nino Index tracks the ocean part. The Southern Oscillation Index compares the difference from average air pressure in the western Pacific, measured in Darwin, Australia, to the difference from average pressure in the central Pacific, measured in Tahiti.

 

The El Nino-Southern Oscillation refers to the fluctuation between El Nino and La Nina conditions in the Pacific Ocean. El Nino is linked to drier and hotter weather in India while La Nina results in more favourable rainfall. 

 

The Indian Ocean Dipole remains in the negative phase but has been weakening steadily over the past three weeks, the bureau said. As of Sunday, the Indian Ocean Dipole stood at (-)0.6 degrees Celsius. The bureau predicts a return to neutral Indian Ocean Dipole conditions in December.

 

The India Meteorological Department had forecast La Nina conditions to persist through December to February before transitioning to neutral El Nino-Southern Oscillation conditions. The Indian weather department also forecast negative Indian Ocean Dipole conditions weakening in the coming months.  End

 

Reported by Shreya Shetty

Edited by Tanima Banerjee

 

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