La Nina weather, which results in heavy rainfall and floods in Asia particularly India, will likely emerge after August only, the Australian Bureau of Meteorology (BoM) indicated today.

Climate models suggest that sea surface temperatures (SSTs) in the central tropical Pacific are likely to continue to cool for at least the next 2 months. “From September, 4 of 7 climate models suggest SSTs are likely to remain at neutral ENSO levels, and the remaining 3 suggest the possibility of SSTs reaching La Niña levels (below −0.8 °C),” it said in its Climate Driver Update on Tuesday. 

The El Niño–Southern Oscillation (ENSO) is currently neutral and  SSTs in the central Pacific have been cooling since December 2023. The cooling has been supported by a cooler-than-average sub-surface in the central and eastern Pacific. 

“During June, the rate and extent of cooling both at the surface and at depth has slowed. Cloud and surface pressure patterns are currently ENSO-neutral,” the Australian weather agency said.

C3S views

Its views reflect those of the Copernicus Climate Change Service (C3S), the earth observation component of the European Union’s Space programme.

C3S said in a press release on Monday that temperatures were below average over the eastern equatorial Pacific, indicating a developing La Niña, but air temperatures over the ocean remained at an unusually high level over many regions.  

The Climate Prediction Center of the US, an arm of the National Oceanic and Atmospheric Administration, said in its latest update that below-average temperatures remain at depth in the central Pacific Ocean, with slightly above-average temperatures near the surface.

‘Watch’ no guarantee

BoM said it had issued a “La Niña Watch” due to early signs that an event may form in the Pacific Ocean later in the year. However, a “La Niña Watch” does not guarantee the development of the weather trend.

“Only that there is about an equal chance of either ENSO remaining neutral or a La Niña developing. Early signs of La Niña have limited relevance to mainland Australia and are better reflections of conditions in the tropical Pacific,” the Australian weather agency said.

In an indication of the problems that weather agencies are facing in predicting the weather pattern, BoM said global SSTs have been the warmest on record for each month between April 2023 and June 2024. “These global patterns of warmth differ to historical global patterns of sea surface temperatures associated with ENSO and IOD; therefore, future predictions based on historical SSTs during past ENSO or IOD events may not be reliable,” it said. 

BoM said phenomena such as ENSO and the IOD are only broad indicators of the expected climate. The long-range forecast provides better guidance on local rainfall and temperature patterns.

IOD neutral

The Indian Ocean Dipole (IOD) is currently neutral. The latest model outlooks indicate that the IOD will remain neutral until at least early spring, beyond which IOD predictability is low, it said.

US’ CPC also reported problems in forecasting weather patterns. “Since mid-March 2024, below-average SSTs have emerged in the eastern Pacific and expanded slightly westward. This area weakened and contracted slightly in June 2024,” it said.

The India Meteorological Department (IMD), too, said La Nina could set in during the south-west monsoon. The deficiency in monsoon rainfall, which was 11 per cent in June, has been wiped off. As of June 9, the monsoon had 1 per cent rainfall above normal. 

However, data from 724 districts show that 33 per cent of these have received deficient rain. 

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