Chennai, October 2: El Niño has strengthened sharply in the tropical Pacific, with the Nino3.4 index reaching 2.72°C for the week ending September 27, making it the second highest weekly value recorded since 2008 according to Australia’s Bureau of Meteorology.
The latest reading is well above the El Niño threshold of 0.8°C and only slightly below the record weekly value of 2.76°C recorded in November 2015.
Climate models indicate that Pacific Ocean temperatures could rise further through October and November. Most models are forecasting the Nino3.4 index to cross 3°C, with the peak potentially occurring between December and February and conditions continuing into early 2027.
Model projections suggest the event could reach levels above the warmest El Niño conditions recorded since reliable observations began in 1950.
At the same time, the Indian Ocean Dipole (IOD) is showing signs of moving towards a positive phase. The IOD index stood at +0.76°C for the week ending September 27, remaining above the positive IOD threshold of +0.4°C for a third consecutive week.
The Bureau said a positive IOD event could develop during the Southern Hemisphere spring and continue into early summer, although there remains uncertainty over its strength and duration.
Atmospheric indicators are also supporting the presence of a strong El Niño. Trade winds have weakened or reversed across parts of the western and central tropical Pacific, while cloud cover has increased over the central and eastern Pacific.
Global ocean temperatures are also at exceptionally high levels. Sea surface temperatures averaged across the region between 60°S and 60°N reached their highest monthly level on record standing 1.04°C above the 1961–1990 average.
The Southern Oscillation Index another indicator of El Niño conditions remained strongly negative. Its latest 30 day value was -20.5 well below the El Niño threshold of -7.
With Pacific waters continuing to warm and the possibility of a positive IOD developing, climate monitoring agencies are closely tracking how the combined ocean and atmospheric conditions evolve through the coming months.