Dateline El Nino
Published on 11 Oct 2025
Tropical Pacific sea surface temperature (SST) patterns have shown an unexpected evolution since early 2024.
Initial forecasts strongly suggested a La Niña developing in the latter half of the year, seemingly supported by early cold SST anomalies in the far eastern Pacific.
However, these cold anomalies strangely shifted westward towards the international dateline, while warm anomalies appeared in the far east by early summer 2024.
Unusual wind patterns accompanied this, with easterly anomalies in the central-western Pacific and westerly anomalies in the far east.
This unusual configuration of cold SSTs west of warm SSTs persists, contrasting with the more common Dateline or Central Pacific El Niño pattern of recent decades.
Dateline El Niño, also known as "El Niño Modoki", refers to climatic phenomena characterized by the warming of sea surface temperatures (SSTs) in the central Pacific Ocean, near the International Date Line.
While La Niña typically has a consistent cold SST pattern in the eastern to central Pacific, El Niños exhibit "flavours" with warm SSTs in either the east or central Pacific.
The underlying cause of this novel SST anomaly pattern remains unknown.
