Six of the seven models suggest that La Nina is unlikely to emerge during November 2024-February 2025, while all models are unanimous that El Nino-Southern Oscillation (ENSO) neutral conditions will prevail by March 2025, Australia’s Bureau of Meteorology (BoM) said on Tuesday.
“The Bureau’s (BoM) model suggests SSTs (sea surface temperatures) are likely to remain within the ENSO-neutral thresholds (−0.8 °C to +0.8 °C) throughout the forecast period to February 2025. Of the 6 other climate models surveyed, only one model suggests SSTs in the tropical Pacific are likely to exceed the La Niña threshold (below −0.8 °C) throughout November to February…,” the Australian weather agency said in its latest Climate Driver Update.
It would be sufficient to be classified as a La Niña event. “All models forecast neutral ENSO values by March,” said BoM.
CPC forecast
This is in contrast to forecasts by the US’ Climate Prediction Center (CPC), which said there was a 60 per cent chance of La Niña emerging in September-November. It is expected to persist through January-March 2025.
The Australian weather agency said ENSO remains neutral in the central equatorial Pacific Ocean. “Atmospheric indices, such as those related to patterns of surface pressure, cloud and trade winds, are broadly consistent with an ENSO-neutral state. While some atmospheric indices have displayed La Niña-like signals over recent months, a consistent/sustained shift has not been observed,” it said.
The Australian weather agency said for the week ended October 27, the latest Indian Ocean Dipole (IOD) index value was −0.94 °C, marking the fifth week close to or below the negative IOD threshold (−0.40 °C).
“The Indian Ocean Dipole (IOD) is neutral. All models indicate that the IOD index will meet or exceed negative IOD thresholds in November,” said BoM. However, they will return to neutral values by December.
Typical IOD phase
Sea surface temperatures (SSTs) were 0.8–2 °C warmer than the 1991–2020 average across much of the central and eastern Indian Ocean during the week-ended October 27. But it was 0.4–2 °C cooler than average in parts of the western Indian Ocean, broadly typical of the ocean pattern associated with a negative IOD phase, said BoM.
The CPC said over the past four weeks, negative SST anomaly changes were evident across most of the equatorial Pacific. In the far eastern Pacific, positive changes were observed.
The US weather agency said over the last couple of months, negative subsurface temperature anomalies have persisted in the eastern equatorial Pacific Ocean and extended to the surface.
Below-average temperatures remain at depth in the east-central Pacific Ocean, while above-average temperatures prevail at depth and near the surface in the western Pacific, the CPC said.
