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Informist, Saturday, Sept. 13, 2025

 

MUMBAI – Private weather forecaster Skymet said a negative Indian Ocean Dipole event is very likely during the withdrawal phase of the southwest monsoon over India. "The Indian Ocean Dipole is in the early stages of a negative IOD phase," it said.

 

Currently, there is a neutral Indian Ocean Dipole. However, the last seven weeks of the Indian Ocean Dipole index have been below the negative Indian Ocean Dipole threshold, the agency said. The latest Indian Ocean Dipole index for the week ended Sunday was (-) 1.27 degrees Celsius.

 

Sustained index values less than or equal to (-) 0.4 degrees Celsius for at least eight weeks are typical of a negative Indian Ocean Dipole. The Indian Ocean Dipole is the difference in surface temperatures between the eastern and western tropical Indian Ocean. A negative Indian Ocean Dipole is a climate phenomenon where the waters on the eastern side of the Indian Ocean become warmer than average, while the western side, near Africa, becomes cooler.

 

A negative Indian Ocean Dipole commencing before or during the onset phase of monsoon tends to suppress the southwest monsoon over India, with more "break days" when there is little or no rainfall, the weather agency said. However, this will increase rainfall over Indonesia and Australia, but lead to a higher risk of drought in eastern Africa.

 

Meanwhile, there is a 55-60% probability of La Nina returning during Oct-Dec, the agency said, citing the World Meteorological Department. The sea surface temperatures in the equatorial Pacific Ocean have already begun to cool and are likely to cool down further. For La Nina to emerge, ocean surface temperatures in the tropical Pacific should meet or fall below the threshold of (-)0.8 degrees Celsius. However, all four Nino indices across the equatorial Pacific have remained under zero degrees Celsius for the third consecutive week, showing a neutral El Nino-Southern Oscillation.   

 

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, hotter weather in India, while La Nina results in more favourable rainfall.

 

The weather agency said the Madden-Julian Oscillation, the major fluctuation in tropical weather on a weekly to monthly timescale, is currently weak and disrupted. The enhanced part of the weather phenomenon is situated over the Western Hemisphere and the western Indian Ocean. "The suppressed phase is located over the Maritime Continent." The overall strength of the phenomenon is not as robust as seen during July and August. The Madden-Julian Oscillation's impact on weather patterns is expected to be minimal in the immediate future.

 

Currently, none of the oceanic parameters favour a strong push for the monsoon current, the weather agency said. "Cool equatorial Pacific nearing La Nina threshold, negative Indian Ocean Dipole conditions, and incoherent Madden-Julian Oscillation, working in tandem, may retard monsoon activity in its closing phase." These events may "hasten" the withdrawal of monsoon, starting with northern India anytime soon. The withdrawal of the southwest monsoon usually begins around Sept. 17 and ends around Oct. 15.  End

 

Reported by J. Navya Sruthi

Edited by Nishant Maher

 

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