Borkotoky et al. (2026) Influence of North American Weather Regimes on Regional Extreme Precipitation Events over CONUS

Identification

• Journal: Journal of Climate
• Year: 2026
• Date: 2026-10-16
• Authors: Swatah Snigdha Borkotoky, Kathleen A. Schiro, Kevin M. Grise
• DOI: 10.1175/jcli-d-25-0528.1

Research Groups

• Department of Environmental Sciences, University of Virginia
• Environmental Institute, University of Virginia

Short Summary

This study defines seasonally-evolving North American Weather Regimes (WRs) and investigates their influence on extreme precipitation events across CONUS watersheds, finding that specific WRs (e.g., persistent upper-level troughs) often trigger extreme precipitation in certain regions.

Objective

• To define seasonally-evolving North American Weather Regimes (WRs) and examine their impact on extreme precipitation events throughout watersheds of the conterminous United States (CONUS).

Study Configuration

• Spatial Scale: Conterminous United States (CONUS) watersheds; North America (for WR definition).
• Temporal Scale: 1980–2022 (43 years).

Methodology and Data

• Models used: Gaussian-mixture-model clustering algorithm.
• Data sources: ERA5 reanalysis dataset (daily 500-hPa geopotential height anomalies).

Main Results

• North American Weather Regimes (WRs) exhibit generally similar spatial patterns across seasons but differ in frequency, persistence, and impacts seasonally.
• Extreme precipitation events across CONUS show distinct seasonality in frequency and dominant driving features.
• Mesoscale convective systems (MCSs) are the primary contributors to extreme precipitation nationwide and in all seasons, often co-occurring with fronts and atmospheric rivers (except in the Southeast during summer).
• Extreme precipitation events in the West Coast, Ohio Valley, and Midwestern regions are frequently triggered by WRs featuring a persistent upstream upper-level trough.
• Conversely, the absence of extreme precipitation in these regions is often associated with WRs featuring a persistent upstream upper-level ridge.

Contributions

• Provides a seasonal definition of North American Weather Regimes, extending beyond previous winter-focused studies.
• Quantifies the distinct seasonal impact of these WRs on extreme precipitation events across CONUS watersheds.
• Highlights the potential for improved long-term forecasts of extreme precipitation, particularly in western and central CONUS, by forecasting North American WRs.

Funding

• Not specified in the provided text.

Citation

@article{Borkotoky2026Influence,
  author = {Borkotoky, Swatah Snigdha and Schiro, Kathleen A. and Grise, Kevin M.},
  title = {Influence of North American Weather Regimes on Regional Extreme Precipitation Events over CONUS},
  journal = {Journal of Climate},
  year = {2026},
  doi = {10.1175/jcli-d-25-0528.1},
  url = {https://doi.org/10.1175/jcli-d-25-0528.1}
}