GFS vs ECMWF Demand-Hub Outlook: 2026-06-11 00Z

Executive Summary

The 15-day outlook indicates a period dominated by cooling demand, with the GFS model projecting a moderately stronger demand signal than the ECMWF. Nationally, the GFS forecasts 148.4 weighted Cooling Degree Days (CDDs), ~7.4 more than the ECMWF's 141.0. This national difference is primarily driven by a significantly warmer GFS outlook for the East, which more than offsets a cooler GFS forecast in the Midwest.

Hub-Level Weather

The largest demand hubs, the Midwest and the East, show significant model disagreement, but in opposite directions.

• East (New York City): This is the main driver of the GFS's national warmth. The GFS projects 171.8 CDDs, a substantial 32.0 CDDs more than the ECMWF's 139.8 CDDs, with most of the divergence occurring after June 21st.
• Midwest (Chicago): In contrast to the East, the ECMWF is significantly warmer in this high-weight (0.35) region, forecasting 103.6 CDDs versus the GFS's 84.6 CDDs.
• South (Atlanta): The GFS is also notably warmer in the South, projecting 201.1 CDDs against the ECMWF's 173.8 CDDs.
• South Central (Houston): Models are in closer agreement, with the GFS showing 267.3 CDDs to the ECMWF's 256.3 CDDs.

Demand Implications (Natural Gas)

The forecast implies a period of sustained summer power burn for cooling, with minimal heating load.

• The GFS solution implies moderately higher natural gas demand for power generation compared to the ECMWF, centered on stronger heat in the eastern U.S. during the 10-15 day period.
• The prior model cycle trend is important: The GFS trended significantly cooler, losing 3.75 weighted CDDs run-over-run, while the ECMWF remained stable (+0.2 CDDs). This model convergence suggests a slightly less bullish demand picture than the previous forecast.

Model Agreement & Caveats

The overall model agreement provides moderate confidence in the near-term forecast, but significant regional divergence later in the period warrants caution.

• Convergence: The national convergence_score is a solid 0.8770, suggesting good agreement on the broad synoptic pattern.
• Caveats: This high-level score masks the significant regional disagreements noted above, particularly in the Midwest and East. The forecast for the final 5 days (June 21-25) carries lower confidence due to this model spread.
• Source Limitations: This analysis is based on deterministic model runs from Open-Meteo, which provides gridded data interpolated to specific hub locations. It does not incorporate ensemble guidance, which would provide a fuller picture of forecast uncertainty.