GFS vs ECMWF Demand-Hub Outlook: 2026-04-01T00:00Z

Executive Summary

The 15-day outlook shows a material disagreement between models, with the GFS forecasting significantly more heating demand than the ECMWF. The GFS projects 219.2 total weighted HDDs versus the ECMWF's 183.1, a difference of 36.1 HDDs. This divergence is driven primarily by a much colder GFS outlook for the high-demand Midwest and East hubs, suggesting a wider range of possible demand outcomes. Both models trended colder compared to their prior runs.

Hub-Level Weather

The primary drivers of the national demand forecast are the Midwest and East, which together account for 75% of the demand weighting in this analysis. The key model disagreements are concentrated in these regions:

• Midwest (Chicago, 35% weight): This is the largest source of model disagreement. The GFS forecasts a cumulative 328.2 HDDs, a substantial 55.1 HDDs more than the ECMWF's 273.1 HDDs.
• East (New York City, 30% weight): The GFS is also colder here, projecting 219.8 HDDs against the ECMWF's 178.9 HDDs, a difference of nearly 41 HDDs.
• South Central (Houston, 15% weight): Models diverge on cooling demand. The GFS is warmer, forecasting 110.9 CDDs, while the ECMWF is cooler with 87.6 CDDs. Both models see minimal heating demand in this region.

Demand Implications (Natural Gas)

The GFS solution implies a notably stronger call on natural gas for residential and commercial heating over the next two weeks compared to the ECMWF. The run-over-run data confirms a bullish demand shift, as both models added significant heating load since the prior cycle (+14.6 weighted HDDs for GFS, +16.4 for ECMWF). This indicates a consensus trend toward higher-than-previously-expected heating demand.

Cooling demand (power burn) is a secondary factor, with the GFS showing slightly more load (21.8 weighted CDDs) than the ECMWF (19.4 weighted CDDs).

Model Agreement & Caveats

Confidence in the forecast is moderate due to material model disagreement. The weighted average daily difference in heating demand is 3.50 HDDs, and the overall convergence score is 0.222, indicating a lack of strong consensus, particularly for the Midwest and East. This suggests that traders should treat the single-model forecasts with caution and consider the potential for significant forecast revisions.

The run-over-run delta shows a slight worsening of model agreement (convergence score +0.0073), reinforcing the need for caution.

Caveats: This analysis is based on Open-Meteo's specific model runs (gfs_seamless, ecmwf_ifs025) and a pre-defined set of demand hubs. It may not capture all regional nuances.