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Warm water weather phenomenon El Nino has developed further over the past four weeks with sea surface temperatures (SSTs) being high across central and eastern Pacific Ocean besides the western Indian Ocean.
US weather agency Climate Prediction Centre (CPC) has said in its recent update that values of the upper-ocean heat anomalies (above average) and thermocline slope index (below average) — the difference in depth of isotherm between western and eastern pacific reflect El Niño.
The agency has increased El Nino chances of continuing through December 2023-February 2024 to 95 per cent.
Anomalies over Indonesia
Positive outgoing longwave radiation (OLR) anomalies — suppressed convection and precipitation — were evident around South-East Asia, the Philippines, and Indonesia. “Since mid-July 2023, positive OLR anomalies have persisted over Indonesia,” said the CPC, an arm of US National Oceanic and Atmospheric Administration (NOAA).
More importantly, the recent Oceanic Nino Index (ONI) value for June-August is 1.1ºC. This is far higher than CPC’s norm, which considers El Nino or La Nina conditions to occur when the monthly Nino 3.4 departures meet or exceed +/- 0.5ºC along with consistent atmospheric features.
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“Nearly all models indicate El Nino will persist through the Northern Hemisphere winter 2023-24. At its peak (November-January), a strong El Nino (ONI values at or greater than 1.5ºC) is indicated by the dynamical model average,” the CPC said.
Erratic Indian monsoon
This is a fair indication of the monsoon playing truant this year with July witnessing above-normal and August experiencing 32 per cent deficient showers.
Typically, El Nino leads to drought and dry weather in Asia. The weather phenomenon seems to be playing out, going by reports from across Asia.
The CPC said during the last four weeks, equatorial SSTs were above average across most of the Pacific Ocean, in the western Indian Ocean, and across much of the Atlantic Ocean.
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Recent values of the upper-ocean heat anomalies (above average) and thermocline slope index (below average) - the difference in depth of isotherm between western and eastern pacific reflect El Nino.
The CPC said since March, positive SST anomalies in the eastern Pacific Ocean have gradually expanded westward. “In the last four weeks, equatorial SSTs were above average across most of the Pacific Ocean, with near average SSTs present in the western Pacific Ocean,” it said.
Over the last four weeks, mostly positive SST anomaly changes were evident across the central and eastern Pacific Ocean. The US weather agency said positive subsurface temperature anomalies dominate most of the equatorial Pacific Ocean.
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