Evaluation of severe weather forecasts from real-time medium-range convection-allowing ensembles over the conterminous United States
Schwartz, C. S., Sobash, R. A., Harris, L. M., Ahijevych, D., Cheng, K., et al. (2026). Evaluation of severe weather forecasts from real-time medium-range convection-allowing ensembles over the conterminous United States. Weather and Forecasting, doi:https://doi.org/10.1175/WAF-D-25-0181.1
| Title | Evaluation of severe weather forecasts from real-time medium-range convection-allowing ensembles over the conterminous United States |
|---|---|
| Genre | Article |
| Author(s) | Craig S. Schwartz, Ryan A. Sobash, L. M. Harris, David Ahijevych, K. Cheng, Matthew Morin, L. ZHOU, A. J. Clark |
| Abstract | During both spring 2023 and 2024, we produced two sets of experimental, real-time, medium-range (3–8 days) convection-allowing ensemble (CAE) forecasts with variable-resolution global models that had 3-km horizontal cell spacing over the conterminous United States (CONUS). One ensemble had 10 members, produced 8.5-day forecasts, and used GFDL’s Continental System for High-Resolution Prediction on Earth-to-Local Domains (C-SHiELD), a prediction model based on the finite-volume cubed-sphere dynamical core. The second ensemble had 5 members, produced 5.5-day forecasts, and used NSF NCAR’s Model for Prediction Across Scales (MPAS). These demonstrations collectively represented the first real-time, medium-range CAE guidance over the CONUS and the first real-time CAE forecasts produced with variable-resolution global numerical weather prediction models. Probabilistic medium-range surrogate severe weather forecasts based on 2–5-km updraft helicity (UH) were objectively verified against observed severe weather reports over the CONUS. For optimal UH thresholds and smoothing length scales, the MPAS and C-SHiELD ensembles produced skillful severe weather forecasts relative to climatology through 5 and 8 days, respectively. Moreover, both sets of medium-range ensemble forecasts typically had higher skill scores than 3–8-day Storm Prediction Center (SPC) outlooks, although comparison of SPC and CAE forecasts should be interpreted cautiously. Numerous forecast examples demonstrate strengths of the medium-range CAE forecasts, as well as some weaknesses. Overall, results suggest great promise of medium-range CAEs for severe weather forecasting applications over the CONUS. |
| Publication Title | Weather and Forecasting |
| Publication Date | Sep 1, 2026 |
| Publisher's Version of Record | https://doi.org/10.1175/WAF-D-25-0181.1 |
| OpenSky Citable URL | https://n2t.net/ark:/85065/d7v129d3 |
| OpenSky Listing | View on OpenSky |
| MMM Affiliations | PARC |