Zhang et al. (2025) Winter Precipitation Predictions in the Contiguous United States: Challenges for Two Seasonal Forecast Models, SEAS5 and CFSv2

⚠️ Warning: This summary was generated from the abstract only, as the full text was not available.

Identification

• Journal: Journal of Climate
• Year: 2025
• Date: 2025-07-16
• Authors: Yingxian Zhang, Qinghua Ding, Hailan Wang, Chan Xiao, Qingchen Chao, Qingquan Li, Guofu Wang
• DOI: 10.1175/jcli-d-24-0608.1

Research Groups

Not specified in the provided text.

Short Summary

This study evaluates the ability of two operational seasonal forecast models (SEAS5 and CFSv2) to predict large-scale circulation modes that modulate winter precipitation in the contiguous United States via atmospheric rivers, finding that the "West mode" is particularly difficult to forecast due to its internal dynamical origins.

Objective

• To assess the skill of operational seasonal forecast systems in replicating the compound effects of three large-scale circulation modes (Pacific–North American [PNA], West, and South) and atmospheric rivers (ARs) on winter precipitation across the contiguous United States (CONUS).

Study Configuration

• Spatial Scale: Contiguous United States (CONUS) and the North Pacific.
• Temporal Scale: Winter season (December–February [DJF]).

Methodology and Data

• Models used: European Centre for Medium-Range Weather Forecasts’ fifth generation seasonal forecast system (SEAS5) and the National Centers for Environmental Prediction’s Climate Forecast System, version 2 (CFSv2).
• Data sources: Reanalysis data (used for observational baseline and evaluation).

Main Results

• Both SEAS5 and CFSv2 can capture some spatial features of the PNA, West, and South modes when initialized on 1 December.
• The models fail to accurately reproduce the temporal variations of these modes, with the most significant failure occurring in the West mode.
• The unpredictability of the West mode is attributed to its driver: barotropic instability related to the subtropical jet stream over the North Pacific, which is insensitive to slowly varying sea surface temperature (SST) changes.
• Due to the failure to simulate the West mode, seasonal forecasts for winter precipitation in the western United States exhibit poor performance.

Contributions

• The research identifies a fundamental limitation in current seasonal forecasting: the inability to predict internally driven circulation modes (specifically the West mode), thereby defining a boundary for the predictability of winter precipitation in the western US.

Funding

Not specified in the provided text.

Citation

@article{Zhang2025Winter,
  author = {Zhang, Yingxian and Ding, Qinghua and Wang, Hailan and Xiao, Chan and Chao, Qingchen and Li, Qingquan and Wang, Guofu},
  title = {Winter Precipitation Predictions in the Contiguous United States: Challenges for Two Seasonal Forecast Models, SEAS5 and CFSv2},
  journal = {Journal of Climate},
  year = {2025},
  doi = {10.1175/jcli-d-24-0608.1},
  url = {https://doi.org/10.1175/jcli-d-24-0608.1}
}