GFS vs ECMWF Demand-Hub Outlook: 2026-07-02 00Z

Executive Summary

The 15-day outlook shows a material model disagreement on the regional distribution of cooling demand. While the ECMWF is hotter on a national weighted basis (236.8 CDDs vs. GFS 217.0 CDDs), this is driven by a significantly warmer forecast for the high-demand Midwest. Conversely, the GFS is the hotter model across the South. Confidence is tempered by a significant run-over-run divergence, with the GFS trending much cooler (-23.4 CDDs) and the ECMWF trending hotter (+10.1 CDDs).

Hub-Level Weather

The primary source of model disagreement is in the Midwest and South Central regions:

• Midwest (Chicago, 35% weight): The ECMWF is substantially hotter, forecasting 222.9 cumulative CDDs versus only 146.7 CDDs from the GFS. The divergence grows significantly in the Day 6-15 period.
• South Central (Houston, 15% weight): The models show an opposing signal, with the GFS forecasting a much hotter outlook at 340.7 cumulative CDDs compared to the ECMWF's 278.6 CDDs. This difference is most pronounced in the final week of the forecast.
• East (New York City, 30% weight): The models are in strong agreement, with both forecasting approximately 233-236 cumulative CDDs, showing consistent heat for the region.

Demand Implications (Natural Gas)

Both models indicate sustained, above-normal cooling demand nationally, but imply different regional stress points for natural gas power burn.

• The ECMWF scenario suggests stronger, more persistent power demand from the critical Midwest and Northeast population centers, which would be broadly supportive of national gas prices.
• The GFS scenario implies more moderate demand in the Midwest but points to stronger heat in Texas and the Southeast. This would place greater stress on ERCOT and Southern gas markets.
• Given the early July timeframe, both forecasts point to a period of robust weather-driven demand with minimal risk of heating load.

Model Agreement & Caveats

• Convergence: The national convergence score is high at 0.988, but this masks significant offsetting regional disagreements. The Midwest is cooler on GFS and hotter on ECMWF, while the South is the inverse. This high-level agreement score should be viewed with caution.
• Run-over-Run Trends: Confidence in the outlook, particularly for the Day 8-15 period, is reduced by the significant model divergence from the prior cycle. The GFS lost ~23.4 weighted CDDs, while the ECMWF gained ~10.1 weighted CDDs, signaling instability in the pattern.
• Source Data: This analysis is based on Open-Meteo's specific grid-point forecasts and weighting. Total CONUS demand may differ based on more comprehensive weighting methodologies.