La Nina Waning Rapidly: May Succumb In March Itself

La Niña conditions persisted through February, and the quarterly ONI (Dec-Jan-Feb) finished at -0.6°C. The index was just a notch higher than the threshold mark of -0.5°C and therefore indicated the continuation of La Niña. However, ENSO-neutral may develop by the end of March or early April and thereafter persist through the Northern Hemisphere summer. In its latest update, the World Meteorological Organization (WMO) also corroborates the weak La Niña event that emerged in Dec 2024 to be short-lived.

The Tropical Pacific has been experiencing surface temperatures less than the average since fall of 2024. Despite La Niña cooling over a large portion of the Pacific, January 2025 was the warmest month on record. Thereafter, India witnessed the warmest February since 1901. Climate scientists say climate change is more robust now, and La Niña may not remain effective in the warmer future. El Niño events may become more common and severe in the future, with climate change driving this new normal of warmer winters and shorter springs.

ENSO: Global models have the potential to predict ENSO months in advance. The associated changes in the global atmospheric patterns are also understood reasonably well. Deep study of ENSO provides an early assessment for potential weather and climate risks in different parts of the globe, including monsoons, floods, droughts, hurricanes, extreme temperatures and crop yields.  

The quarterly index (ONI) in the Nino 3.4 region continue to remain slightly below the threshold of -0.5°C.  As anticipated in the previous article,  the latest value of ONI for the quarter Dec-Jan-Feb is -0.6°C and therefore, is the key indicator of La Nina. The IRI ENSO plume forecasts equal chances (50%) for La Nina and ENSO-neutral conditions for Feb-Mar-Apr 2025.  For Mar-Apr-May 2025 onwards to the Jun-Jul-Aug, ENSO-neutral conditions are favoured. The next two forecast seasons, Jul-Aug-Sep and Aug-Sep-Oct 2025, do not show a strong preference for La Nina or ENSO-neutral.  Currently, the entire tropical Pacific has warmed up and all the Nino indices have risen appreciably from the previous week record.  Nino 3 and Nino 1+2 have together, breached the positive threshold mark of 0.5°C, for the second consecutive week, since March 2024.  Nino 3.4 index has turned positive, for the first time since July 2024. The latest weekly value of the index as on 17thMar 2025 was +0.3°C. At this rate, the La Nina may collapse earlier than expected.

IOD:  The Indian Ocean Dipole has generally remained within the threshold of +/- 0.4°C during this year. The index was bounded by negative values in Jan 2025, which later turned positive in Feb 2025.  In March so far, the index remained marginally positive. The latest value of the index for the week ending 16March2025 was +0.21°C. Even, with the best of technical assistance, prediction of IOD beyond 4 weeks lacks credibility.

MJO:  The Madden-Julian Oscillation is likely to propagate eastward from Indian Ocean to the Maritime Continent, during the remaining days of March 2025.  The amplitude is going to shrink and therefore, loosing potential for any significant convective activity.  Wavering of La Nina conditions in the Pacific Ocean will adversely  impact the existence of MJO. Currently, there is very limited stormy activity on either side of the equator.  There is only one invest area, south of equator,  in the Western Indian Ocean, which may intensify into a cyclonic storm. Indian seas are likely to remain passive during the forecast period of March 2025.

ENSO-neutral conditions are favoured during the Indian Summer Monsoon.  The probability of El Nino remains very low throughout the forecast period. IOD forecast can not be made, months in advance and a realistic picture will emerge, not earlier than May 2025. An early withdrawal of La Nina conditions is quite likely.  The ONI for the quarter Jan-Feb-Mar may drop below the threshold mark of -0.5°C.