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Informist, Wednesday, Jul. 29, 2026

MUMBAI – The Indian Ocean Dipole, which is currently neutral, reached the positive threshold in the week ended Sunday, the Australian Bureau of Meteorology said in its fortnightly report on Tuesday. This marks the first week that the Indian Ocean Dipole has been positive, but sustained values above this threshold are required before an event is considered to be established. International climate models indicate a positive event could develop during the Southern Hemisphere winter and persist into spring, the weather bureau said.

Winter in the Southern Hemisphere spans from June to August, and spring from September to December.

However, some variations in climate models' forecasts about the timing and strength of a positive Indian Ocean Dipole event remain, the weather bureau said. As of Sunday, the weekly Indian Ocean Dipole Index was 0.44 degrees Celsius, having warmed by around 0.5 degrees Celsius in the past fortnight, the bureau said. Sustained values above 0.4 degrees Celsius are indicative of a positive event. 

The Indian Ocean Dipole is the difference in surface temperatures between the eastern and western tropical Indian Ocean. A negative Indian Ocean Dipole leads to less rainfall in India, while a positive index leads to more rainfall. A positive Indian Ocean Dipole could mitigate some effects of an El Nino event on the southwest monsoon in India.

The El Nino event has been underway since mid-June, and continues to strengthen, with further intensification likely in the coming months, the weather bureau said. International models' forecasts point to a strong to very strong El Nino based on the warming in the central Pacific Ocean. The majority of these models indicate that the event is likely to peak at levels among, or above, the highest observed since 1950, the bureau said.

As of Sunday, the El Nino-Southern Oscillation index was 1.95 degrees Celsius, well above the El Nino threshold of 0.80 degrees Celsius, warming by around 0.5 degrees Ceslius in the past fortnight. Atmospheric indicators, such as trade winds, pressure, and cloud patterns are at levels consistent with El Nino.

All international climate models, including the bureau's, forecast the tropical Pacific Ocean to continue warming through the Southern Hemisphere spring, likely peaking in late spring or summer. The strength of this El Nino event, in addition to the typical life cycle of such an event, suggests that it is likely to stretch into the Southern Hemisphere autumn. Summer in the Southern Hemisphere spans from January to March, and autumn from April to June.  

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 is associated with more favourable rainfall.

Though rainfall in India in July is likely to end at near-normal levels, the monsoon season's deficit is expected to remain at 15%. Although El Nino conditions are expected to persist through the remainder of the southwest monsoon season ending September, some global models indicate the Indian Ocean Dipole turning positive in the second half of the season, or Aug-Sept, the India Meteorological Department said.  End

Reported by Shreya Shetty

Edited by Avishek Dutta

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