Europe/Western Russia Week 2-4 Outlook: Mild forecast; Dry across Europe.
01/08/2025, 11:38 am EST
Executive summary: The Climate Impact Company ENSO Outlook for 2025 indicates La Nina will continue through Q1/2025 and weaken during Q2/2025 followed by neutral ENSO. Late in 2025, forecast confidence is low as a weak El Nino could emerge, ENSO remains neutral, or a second La Nina generates. The DEC-24 subsurface equatorial East Pacific cooled dramatically and trails only 2008 and 2010 for coolest upper ocean heat anomalies during December for all La Nina events this century.
Discussion: Given the SLOW developing La Nina in 2024, somewhat surprising is the emergence of the 3rd coolest of this century equatorial East Pacific upper ocean heat signature during DEC-24 (Fig. 1). The coolest December’s were in 2008 and 2010. In total, 10 months of December in this century have produced cool upper ocean heat signatures. NOAA/CPC initiated La Nina onset in their ENSO Report issued this morning as both Nino34 SSTA and multivariate ENSO index (MEI) aligned within the La Nina threshold (Fig. 2). Normally, cool subsurface temperatures in the eastern equatorial Pacific support and maintain La Nina. Based on the 10 cold December subsurface signatures of this century, the following year Nino34 SSTA generally trend out of La Nina during the middle third of the year (Fig. 3). ENSO phase change is common during quarter 2. However, the 2 strongest subsurface cold months of December rendered a split decision between the return of La Nina late the following year or a shift toward El Nino. The 2 weakest subsurface cold months of December was followed by an El Nino developing late the following year. From an analog standpoint, La Nina should end during Q2/2025 followed by neutral ENSO and uncertainty for Q4/2025 ENSO phase. The dynamic models from NOAA agree with the analog assessment favoring La Nina fading during Q2/2025 with neutral ENSO to follow (Fig. 4). By late forecast period, the La Nina risk is slowly increasing.
Fig. 1: Suddenly, the upper ocean heat in the equatorial East Pacific is 3rd coolest for all La Nina events in this century.
Fig. 2: Finally, in December 2024, the Nino34 SSTA and multivariate ENSO index are aligned in the La Nina category.
Fig. 3: Given the cool subsurface in December, the following year Nino34 SSTA are indicated. The strongest cool December subsurface, similar to 2024, yielded a (surprising) 3-1 risk of El Nino later the following year.
Fig. 4: NOAA dynamic models Nino34 SSTA probability forecast through Q3/2025.