GFS vs ECMWF Demand-Hub Outlook: 2026-07-08T00:00Z

Executive Summary

The GFS and ECMWF models are in close alignment on the national 15-day cooling demand outlook, with total weighted CDDs of 216.5 (GFS) and 212.1 (ECMWF). However, this top-level agreement conceals significant regional disagreements. The ECMWF is notably hotter in the high-demand Midwest and Northeast, while the GFS projects substantially more heat across the South and South Central regions. Confidence is tempered by the models trending in opposite directions run-over-run, with the GFS adding significant demand (+11.1 CDDs) and the ECMWF turning cooler (-5.2 CDDs).

Hub-Level Weather

The national forecast is a composite of conflicting regional outlooks driven by the most heavily weighted hubs:

• Midwest (Chicago, 35% weight): This is a key area of disagreement. The ECMWF is significantly hotter, forecasting 222.1 CDDs versus the GFS's 202.6. The divergence is most pronounced from July 14-16, where the ECMWF shows mean temperatures in the low 90s while the GFS remains in the upper 70s.
• East (New York City, 30% weight): While the cumulative 15-day CDDs are nearly identical (GFS: 197.6, ECMWF: 196.9), there are major timing differences. The ECMWF shows a sharp heat spike around July 16 that the GFS misses.
• South/South Central (Houston & Atlanta, 25% combined weight): The GFS is materially hotter in these regions. For Houston, the GFS forecasts 317.0 CDDs against the ECMWF's 264.3. This is driven by the GFS maintaining intense heat late in the period while the ECMWF moderates.

Demand Implications (Natural Gas)

The forecast points to strong and sustained cooling demand, which will support robust natural gas consumption for power generation (power burn).

• The key uncertainty for national demand is which regional forecast proves more accurate.
• If the ECMWF solution verifies, stronger-than-expected power burn would be concentrated in the Midwest (MISO) and Northeast (PJM/ISO-NE) during the Day 7-9 period.
• If the GFS solution is correct, a more prolonged period of strong demand will be centered in gas-heavy power markets like ERCOT and the Southeast.

Model Agreement & Caveats

The national convergence score of 1.0 is misleading. While it reflects the near-identical total weighted CDD forecasts, it completely masks the underlying regional conflicts.

• Run-over-Run Shift: Confidence in the outlook is reduced by the models' opposing trends versus the prior cycle. The GFS trended significantly hotter (+11.1 weighted CDDs), while the ECMWF trended cooler (-5.2 weighted CDDs). This instability suggests the pattern, especially in the 8-15 day range, is not yet settled.
• Open-Meteo Source: This analysis is based on single, deterministic model runs. It does not incorporate ensemble guidance, which would provide a fuller picture of the range of possible outcomes and the level of support for each model's respective solution.