La Nina, rain-bearing weather event in Asia and India in particular, is unlikely before the last week of September 2024, when the Southern Hemisphere spring begins, Australia’s Bureau of Meteorology (BoM) has said.
“ENSO (El Nino-Southern Oscillation) is likely to remain neutral until at least early spring. Three of 7 climate models suggest the possibility of SSTs reaching the La Niña threshold (below −0.8 °C) by October. The remaining 4 models suggest a continuation of ENSO-neutral throughout the forecast period,” it said in its climate update driver on Tuesday.
Spring begins on September 22 in the southern hemisphere. BoM forecast is line with the US Climate Prediction Center’s (CPC) outlook that a transition to La Niña (from the current ENSO neutral conditions) is likely around August-October 2024, while the average of the statistical models predicts ENSO neutral.
Steady cooling
On Monday night, the US weather agency said the most-recent Ocean Nino Index value (April-June 2024) is 0.4ºC. CPC considers El Niño or La Niña conditions to occur when the monthly ONI departures meet or exceed +/-0.5ºC along with consistent atmospheric features. These anomalies must also be forecast to persist for 3 consecutive months.
BoM said ENSO is currently neutral and sea surface temperatures (SSTs) in the central equatorial Pacific Ocean are ENSO-neutral, following a steady cooling from El Niño levels since December 2023.
“This cooling is being sustained by deep waters surfacing in the central and eastern Pacific. However, the rate and extent of cooling both at and below the surface has decreased since May. Atmospheric patterns, including cloud and trade winds, are currently ENSO-neutral,” it said.
‘La Nina watch’
However, the Australian weather agency said ENSO outlook remains at La Niña Watch. “La Niña Watch does not guarantee La Niña development, only that there is about an equal chance of ENSO remaining neutral or La Niña developing during the remainder of 2024,” the weather agency said.
The Indian Ocean Dipole (IOD) is currently neutral. The latest model outlooks indicate that the IOD is likely to remain neutral until at least the end of winter (August 2024).
“Three of 5 climate models suggest that during spring, negative IOD development is likely, while 2 forecast a neutral or positive state of the IOD,” the Australian agency said.
La Nina was initially forecast to emerge in July but the slowing of the cooling in the sea surface temperature has delayed the event. La Nina usually succeeds El Nino, which ended in April.
El Nino, which emerged in June 2023, resulted in global temperatures rising to a record for 13 consecutive months till June. It also resulted in a quarter of India being affected by drought besides impacting agricultural production.