Asik SyedThe tropical Pacific has recently shifted into an ENSO-neutral phase, according to the latest update from the National Oceanic and Atmospheric Administration (NOAA). This change marks the conclusion of a weak La Niña episode and signals a critical period for monitoring global weather developments. ENSO—short for El Niño-Southern Oscillation—plays a key role in shaping climate patterns worldwide, making its phases a focal point for climate forecasting.
Understanding ENSO and Its Phases
ENSO comprises three distinct phases:
- El Niño – Noted for warmer-than-average sea surface temperatures in the central and eastern Pacific.
- La Niña – Characterized by cooler-than-normal waters in the same regions.
- Neutral – A phase where neither warm nor cool anomalies dominate, often acting as a transitional state between the two.
Each phase brings unique climate impacts, affecting weather systems across the globe.
Current State: ENSO Neutral Conditions in April 2025
Recent data from April 2025 reveal that sea surface temperatures (SST) in the Niño-3.4 region are averaging near normal—specifically, at -0.01°C. This value is above the La Niña threshold of -0.5°C, confirming the region’s neutral status. The transition has been driven by westward expansion of warmer surface waters and a decline in the upwelling of cooler subsurface waters.
Atmospheric Impacts of ENSO Neutrality
During neutral phases, atmospheric pressure patterns shift. Higher surface air pressure builds in the central Pacific, while lower pressure persists to the west. This imbalance generates an east-to-west airflow that influences ocean surface currents, reinforcing westward water movement.
Marine Ecosystems and Ocean Health
ENSO-neutral conditions support coastal upwelling along South America’s western edge, delivering nutrient-rich waters that sustain marine biodiversity and benefit fisheries. Simultaneously, cooler waters in the eastern Pacific contribute to drier-than-average weather along nearby coastlines.
Outlook: What Lies Ahead
Climate models suggest a strong likelihood—greater than 50%—that neutral conditions will persist through the summer in the Northern Hemisphere. As the year progresses into fall, predictions become less certain. Current estimates place:
- 43% chance of continued neutral conditions into early winter
- 38% probability of La Niña returning
- Less than 20% likelihood of El Niño developing
Reflecting on the Recent La Niña
Though recently concluded, the latest La Niña was relatively mild and short in duration. It didn’t meet NOAA’s full criteria for classification, which calls for sustained cooler SSTs over five overlapping three-month periods. Nonetheless, it may still be acknowledged in revised historical climate datasets.
Neha Baruah
