Some oceanic indices besides cloud and wind patterns in the Pacific Ocean have, at times, shown weak La Nina characteristics in recent months, Australia’s Bureau of Meteorology (BoM) has said. 

However, it said the negative Indian Ocean Dipole (IOD), which emerged in mid-October, has turned neutral in December.

“The El Niño–Southern Oscillation (ENSO) is currently in the neutral range,” it said in its latest climate update, adding it is not meeting typical La Nina thresholds. 

• Also read: Negative IOD may be underway if index remains below threshold for another week, says BoM

Neutral till April

The Australian weather agency said its model forecasts that ENSO will remain in the neutral range throughout its forecast period to April 2025. This is consistent with 4 of the 6 other international climate models surveyed.

On IOD, BoM said, “The IOD had been tending negative from mid-October but returned to neutral values at the start of December,” said BoM.

The weather agency said its model forecasts that the IOD will remain neutral throughout the forecast period to April 2025. “This is consistent with 5 of the 6 other international climate models surveyed,” it said.

• Also read: 6 weather models point to La Nina not emerging during Nov-Feb, says Australia’s BoM

India feels negative IOD impact

Two weeks ago, BoM predicted that negative Indian Ocean Dipole (IOD) or Indian Nino, a climate phenomenon similar to the El Nino, was underway as the IOD index remained below –0.4 °C since mid-October. 

To be classified as a negative IOD event, the IOD index needs to be at values below the negative IOD threshold (–0.4 °C) for at least 8 weeks. However, the index has turned neutral within the eight weeks. 

IOD is the fluctuation of sea temperature between the western and eastern parts. A positive IOD can result in increased rainfall in parts of India. However, negative IOD will result in lower rainfall in the western parts of India, while the Bay of Bengal will likely witness above-normal cyclonic activity. 

India has felt the impact of negative IOD with a third low-pressure area developing over the Bay of Bengal within a month.

Also, over 60 per cent of the 720 districts in the country received deficient or no rainfall post-monsoon rainfall from October 1 to December 9. 

• Also read: Chance for La Nina to emerge has decreased, says Australia’s BoM

CPC forecast 

A forecast by the Australian Bureau of Agricultural and Resources Economics has predicted below-normal winter rainfall for India. However, Indian agricultural officials say the current spell of rains in the north-west region and snowfall in the hills will likely help rabi crops.

The Climate Prediction Center (CPC) of the US, an arm of the National Oceanic and Atmospheric Administration, also reported ENSO-neutral conditions currently. It said there was a 57 per cent chance of La Nina emerging and could persist through January-March 2025. 

Weather monitoring agencies have faced problems in pinpointing the emergence of La Nina due to the “sustained nature of global ocean heat”. BoM said this suggested that climate indicators such as ENSO and IOD may not behave or evolve as they have in the past.