The El Niño Briefing #13: +3.4 °C, a fourth record in five weeks

NOAA's weekly Niño 3.4 reached +3.4 °C for the week centred 21 October. That's the fourth new high in five weeks: +3.1 °C, then +3.2, then +3.3, and now +3.4. The file goes back to September 1981, and no week outside this year got above +3.0 °C.

This week in one line: Niño 3.4 +3.4 °C · Niño 3 +4.3 °C · Bureau of Meteorology +2.88 °C · RONI +1.69 (Jul–Sep) · CPC 83% for a historic Oct–Dec (8 Oct).

The Bureau set a record too. The Bureau of Meteorology's relative Niño 3.4, which takes out the warming of the tropical oceans as a whole, read +2.88 °C for the week ending 25 October. Its series starts in 2008, and the old high was +2.81 °C, earlier this month.

Further east, higher still. Niño 3 rose to +4.3 °C, another high; its best week before this year was +3.3 °C, in November 1997. Niño 1+2, off Peru and Ecuador, held at +5.2 °C.

The same week in 1997 and 2015. Niño 3.4 read +2.0 °C in the week centred 22 October 1997 and +2.3 °C in the week centred 21 October 2015.

What the models say. IRI's model plume of 19 October gathers 27 models. All of them keep a very strong El Niño (+2.0 °C or more) from October–December through December–February, and their average reaches about +3.5 °C in October–December and November–January. The forecast page →

On the ground: the Philippines. PAGASA, the Philippine weather service, says a strong to very strong El Niño is under way and may peak before the end of 2026. Its advisory of 7 October counted seven provinces in meteorological drought in September, three under a dry spell and thirty with dry conditions. Four weather stations broke their September heat records, Borongan in Eastern Samar among them, at 37.7 °C on 3 September. For October the agency expected below-normal rain over most of Luzon, the Visayas and the Caraga Region, and drought or dry spells by the end of the month across most of the Bicol Region, Eastern Visayas, Surigao del Norte and the Dinagat Islands. Typhoons can still bring heavy rain, PAGASA adds. It asked government offices and the public to prepare now, above all in areas vulnerable to dry spells and heat. How El Niño plays out in the Philippines →

Next. NOAA's weekly file updates on Monday 2 November with the week centred 28 October. CPC's next discussion is due on 12 November.

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— The El Niño Briefing