3 Jun 2025

Development and Validation of NOAA’s 20-Year Global Wave Ensemble Reforecast

Abstract: A 20-yr wave reforecast was generated based on the NOAA Global Ensemble Forecast System, version 12. It was produced using the same setup as the NCEP’s operational GEFSv12 wave component. The reforecast comprises five members with 1 cycle per day and a forecast range of 16 days. Once a week, it expands to 35 days and 11 members. This paper describes the development of the wave ensemble reforecast, focusing on validation against buoys and altimeters. The statistical analyses demonstrated very good performance in the short range for significant wave height, with correlation coefficients of 0.95–0.96 on day 1 and between 0.86 and 0.88 within week 1, along with bias close to zero. After day 10, correlation coefficients fall below 0.70. The degradation of predictability and the increase in scatter errors predominantly occur in the forecast lead time between days 4 and 10, in terms of the ensemble mean and individual members, including the control. For week 2 and beyond, a probabilistic spatiotemporal analysis of the ensemble space provides useful forecast guidance. Our results provide a framework for expanding the usefulness of wave ensemble data in operational forecasting applications.

3 Jun 2025

Development of a Wave Model Component in the First Coupled Global Ensemble Forecast System at NOAA

Abstract: We describe the development of the wave component in the first global-scale coupled operational forecast system using the Unified Forecasting System at NOAA, part of the U.S. National Weather Service operational forecasting suite. The operational implementation of the atmosphere–wave coupled Global Ensemble Forecast System, version 12, was a critical step in NOAA’s transition to the broader community-based UFS framework. GEFSv12 represents a significant advancement, extending forecast ranges and empowering the NWS to deliver advanced weather predictions with extended lead times for high-impact events. The integration of a coupled wave component with higher spatial and temporal resolution and optimized physics parameterizations enhanced forecast skill and predictability, particularly benefiting winter storm predictions of wave heights and peak wave periods. This endeavor encountered challenges addressed by the simultaneous development of new features that enhanced wave model forecast skill and product quality and facilitated by a team collaborating with NOAA’s operational forecasting centers. The GEFSv12 upgrade marks a pivotal shift in NOAA’s global forecasting capabilities, setting a new standard in wave prediction. We also describe the coupled GEFSv12-Wave component impacts on NOAA operational forecasts and ongoing experimental enhancements, which represent a substantial contribution to NOAA’s transition to the fully coupled UFS framework.