New Delhi: La Nina conditions are likely to develop in the next three months but the phase is expected to be relatively weak and short-lived, the World Meteorological Organisation (WMO) said on Wednesday.
Latest forecasts from WMO Global Producing Centres of Long-Range Forecasts indicate a 55% likelihood of a transition from the current neutral conditions (neither El Niño nor La Niña) to La Nina conditions during December 2024 to February 2025. The return of the ENSO-neutral conditions is again likely during February-April 2025, with about 55% chance, WMO said.
La Nina refers to the large-scale cooling of the ocean surface temperatures in the central and eastern equatorial Pacific Ocean, coupled with changes in the tropical atmospheric circulation, such as winds, pressure and rainfall. El Nino is just the opposite, it represents the warm phase of the El Nino/Southern Oscillation (ENSO) cycle.
In India, an El Nino is associated with harsher summer and weaker monsoon. La Nina, meanwhile, is associated with strong monsoon and above average rains and colder winters.
Climate events
However, naturally occurring climate events such as La Nina and El Nino events are taking place in the broader context of human-induced climate change, which is increasing global temperatures, exacerbating extreme weather and climate, and impacting seasonal rainfall and temperature patterns, WMO warned.
“The year 2024 started out with El Niño and is on track to be the hottest on record. Even if a La Niña event does emerge, its short-term cooling impact will be insufficient to counterbalance the warming effect of record heat-trapping greenhouse gases in the atmosphere,” said WMO Secretary-General Celeste Saulo in a statement.
“Even in the absence of El Niño or La Niña conditions since May, we have witnessed an extraordinary series of extreme weather events, including record-breaking rainfall and flooding which have unfortunately become the new norm in our changing climate,” added Celeste Saulo.
HT reported on October 2 that nearly all global forecasters got the La Nina forecast wrong this year. US’s National Oceanic and Atmospheric Administration issued La Nina watch in May, indicating that La Nina conditions are expected to be established soon.
But, till October there was no clarity if it will be established in winter or ENSO neutral conditions will continue. Most circulation features however match that of La Nina, experts said.
“One reason could be global warming that did not help that kind of cooling. Another possibility WMO saying is atmospheric conditions in September and October were not favourable for cooling in the Pacific. But, we need to worry models did not pick up this signal properly,” said M Rajeevan, former secretary, ministry of earth sciences.
As of the end of November 2024, oceanic and atmospheric observations continue to reflect ENSO-neutral conditions which have persisted since May. Sea surface temperatures are slightly below average over much of the central to eastern equatorial Pacific. However, this cooling has not yet reached typical La Niña thresholds. One possible reason for this slow development is the strong westerly wind anomalies observed for much September to early November 2024, which are not conducive for La Niña development. The previous Update, issued in September, forecast a 60% likelihood of la Niña in December-February, WMO said.
Seasonal forecasts for El Niño and La Niña and the associated impacts on the climate patterns globally are an important tool to inform early warnings and early action.
