GFS vs ECMWF Demand-Hub Outlook: 2026-06-25 00z

Executive Summary

Both the GFS and ECMWF models project a strong and sustained period of cooling demand over the next 15 days, with a nearly identical national outlook (214.7 vs. 215.5 weighted CDDs, respectively). However, this national agreement masks significant regional differences, with the ECMWF showing much stronger demand in the Midwest while the GFS is hotter in the East and South. Confidence in the overall demand signal is high, supported by an excellent convergence score of 0.997.

Hub-Level Weather

The national demand forecast is primarily driven by the two largest weighted hubs, the Midwest and the East, which show considerable model disagreement.

• Midwest (Chicago, 35% weight): This is the main point of contention. The ECMWF is significantly hotter, forecasting 225.1 cumulative CDDs versus the GFS's 196.6. The largest divergence appears in the Day 10-12 period (July 4-6).
• East (New York City, 30% weight): The models are reversed here, with the GFS showing higher demand. The GFS projects 205.3 cumulative CDDs compared to the ECMWF's 193.1, largely driven by a GFS heat spike around July 3rd.
• South Central (Houston, 15% weight): The GFS is also materially hotter in this region, forecasting 307.4 CDDs to the ECMWF's 281.8.

The ECMWF's significant heat in the high-demand Midwest hub is effectively offset by the GFS's hotter outlook across the East and South, resulting in the close national total.

Demand Implications (Natural Gas)

The forecast implies a period of robust, above-average natural gas demand for power generation (power burn) through early July. With zero heating demand projected and significant cooling demand across all major hubs, natural gas will be the marginal fuel for meeting air conditioning load. While both models trended slightly cooler compared to their prior runs (GFS -2.3 wCDD, ECMWF -1.6 wCDD), the absolute level of forecast demand remains firmly supportive of prices.

Model Agreement & Caveats

Confidence in the top-level demand forecast is very high, as indicated by the near-perfect convergence score of 0.997. This score improved by +0.029 from the previous cycle, suggesting the models are moving closer together on the national picture.

• Caveats: While national agreement is high, the significant regional disagreements between the models warrant caution for basis traders. The Midwest vs. East/South divergence is a key risk to monitor in subsequent model runs.
• Source Limitations: This analysis is based on deterministic model runs from Open-Meteo for a limited set of demand hubs. It does not incorporate ensemble guidance or a full CONUS-wide analysis.