US weather agency has reduced the chances of La Nina emerging before December.

The Climate Prediction Center (CPC), a branch of the US National Oceanic and Atmospheric Administration (NOAA), has further reduced the chances of La Niña emerging before December. It expects the weather phenomenon, which brings heavy rainfall to India and other parts of Asia, to last through January-March 2025.

In its latest update, the CPC still maintained a La Niña watch, although the probability dropped to 57 percent from 60 percent last month and 66 percent the year before.

Contrary to the CPC’s prediction, Australia’s Bureau of Meteorology said earlier this week that La Nina is unlikely to emerge until February 2025.

Short duration event?

“The IRI (International Research Institute for Climate and Society) plume predicts a weak and short-duration La Niña, as indicated by Nino-3.4 index values ​​less than -0.5C. The latest North American Multi-Model Ensemble (NMME) forecasts are cooler than the IRI plume and predict a weaker La Niña, the US weather agency said.

It added that due to La Niña-like atmospheric circulation anomalies in the tropics, “the team still favors the onset of La Niña”, but it is likely to be weaker and of shorter duration than other historical events.

“A weak La Niña will likely result in less traditional winter impacts, although forecast signals may still influence forecast guidance (for example, the CPC’s seasonal outlook),” the CPC said.

IOD may emerge in November

ENSO-neutral October continued, as shown by overall near-average sea surface temperatures (SSTs) observed over the central and eastern equatorial Pacific Ocean. Similar to September, the latest weekly Niño index ranged from +0.2C (Niño-4) to -0.3C.

Subsurface temperatures remain below average in the east-central and eastern equatorial Pacific Ocean. It states that collectively, the coupled ocean-atmosphere system reflects ENSO-neutrality.

Projecting that La Nina is unlikely to emerge before February 2025, the BOM said the negative Indian Ocean Dipole (IOD) is likely to emerge this month and continue till December.

Initially, La Nina was expected to emerge in July this year but meteorological agencies have observed that the weather phenomenon is yet to emerge. BOM said the persistent nature of significant global ocean warming suggests that climate indicators such as ENSO (El Niño Southern Oscillation) and the IOD may not behave or evolve as in the past.