Northern Hemisphere Climate Drivers Early January
12/26/2025, 8:13 am EST
The Warming Oceans Increasingly Contributing to High Impact Weather/Climate in 2025
12/31/2025, 9:58 am EST
Climate Impact Company Weekly ENSO Climate Diagnostics
Issued: Monday December 29, 2025, Happy Holidays!
Highlight: Changeable La Nina weakened last week, likely past peak intensity.
Fig. 1: The 12-week monitoring of the Nino SSTA regions and subsurface temperature anomaly schemes across the equatorial Pacific Ocean.
Discussion: Last week, the Nino SSTA regions warmed too near, or warmer than the La Nina threshold (Fig. 1). Implied is the short duration late 2025 La Nina episode is past peak intensity. Upper ocean heat is steadily diminishing in the equatorial East Pacific, a definite sign that La Nina is losing cool fuel to sustain intensity into the New Year (Fig. 2). A (warm) Kelvin Wave has shifted well east of the Dateline in the subsurface of the equatorial region. Further eastward progression of this feature will cause La Nina to weaken further. The ECMWF Nino34 SSTA forecast continues to indicate El Nino risk with onset by MAY or JUN of 2026 (Fig. 3).
Fig. 2-3: Upper ocean heat across the equatorial Pacific Ocean east of the Dateline and the ECMWF Nino34 SSTA forecast.