Vorobeva et al. (2026) On the reliability of seasonal snow forecasts

Identification

• Journal: ˜The œcryosphere
• Year: 2026
• Date: 2026-08-21
• Authors: Ekaterina Vorobeva, Yvan Orsolini, Patricia de Rosnay, Jonathan J. Day, Retish Senan, Damien Decremer, Frédéric Vitart
• DOI: 10.5194/tc-20-4605-2026

Research Groups

• NILU (Norwegian Institute for Air Research)
• European Centre for Medium-Range Weather Forecasts (ECMWF)

Short Summary

This study evaluates the reliability of seasonal snow forecasts produced by the ECMWF, a state-of-the-art ensemble dynamical prediction system. The reliability assessment is performed using two independent SWE datasets: ERA5-Land and ESA Snow-CCI v4.

Objective

• Investigate the consistency between forecast probabilities and observed frequencies for binary events representing low- and high snow accumulation winters

Study Configuration

• Spatial Scale: Global, with a focus on eight land regions in the Northern Hemisphere non-mountainous regions
• Temporal Scale: Winter season (December–January–February, DJF) over 30 years (1993–2022)

Methodology and Data

• Models used: ECMWF Seasonal forecasting System (SEAS5)
• Data sources: ERA5-Land reanalysis and ESA Snow-CCI version 4

Main Results

• The reliability assessment shows that the ECMWF seasonal snow hindcasts consistently yield marginally useful to perfect reliability categories for both low- and high-snow conditions independently of the chosen benchmark.
• The results show sensitivity to the choice of verification dataset, with ERA5-Land yielding higher reliability categories than ESA Snow-CCI.

Contributions

• This study fills a gap in the evaluation of probabilistic snow forecasts using reliability assessment.
• The results provide insights into the performance of the ECMWF seasonal forecasting system for snow variables.

Funding

• Copernicus Climate Change Service (C3S) project
• European Union's Horizon 2020 research and innovation program

Citation

@article{Vorobeva2026reliability,
  author = {Vorobeva, Ekaterina and Orsolini, Yvan and Rosnay, Patricia de and Day, Jonathan J. and Senan, Retish and Decremer, Damien and Vitart, Frédéric},
  title = {On the reliability of seasonal snow forecasts},
  journal = {˜The œcryosphere},
  year = {2026},
  doi = {10.5194/tc-20-4605-2026},
  url = {https://doi.org/10.5194/tc-20-4605-2026}
}