GFS vs ECMWF Demand-Hub Outlook: 2026-04-24 00Z

Executive Summary

The 15-day forecast reveals a significant disagreement between models, with the GFS projecting a much colder and more supportive demand outlook than the ECMWF. This divergence is driven primarily by the 6-15 day period in the Midwest and East. The ECMWF's latest run shifted dramatically warmer (-49.7 weighted HDDs), a strongly bearish signal that reduces overall forecast confidence.

Hub-Level Weather

The primary drivers of the national forecast are the Midwest and East, which show a stark model split.

• Midwest (Chicago, 35% weight): The GFS is substantially colder, forecasting 194.2 cumulative HDDs versus the ECMWF's 128.7 HDDs. The disagreement is most pronounced from May 5th onward, where the GFS sees a late-season cold shot while the ECMWF trends much warmer.
• East (New York City, 30% weight): A similar pattern exists, with the GFS forecasting 181.7 HDDs against the ECMWF's 129.4 HDDs. The models diverge significantly after the first week.
• South Central (Houston, 15% weight): Both models show consistent cooling demand. The GFS is slightly stronger with 164.6 cumulative CDDs compared to the ECMWF's 137.3 CDDs.

Demand Implications (Natural Gas)

The conflicting model solutions present opposing implications for natural gas demand and storage injections.

• GFS Scenario (150.8 wHDDs): This forecast implies a notable extension of the heating season, which would support natural gas consumption and slow the pace of inventory builds. This is a bullish weather outlook relative to seasonal norms.
• ECMWF Scenario (103.6 wHDDs): This outlook is significantly more bearish, suggesting a rapid decline in heating needs. The massive warmer revision in this cycle (-49.7 wHDDs) will likely pressure the market, as it points to a faster rate of storage injections.
• Overall: The total demand-weighted picture shows the GFS forecasting 47.2 more HDDs than the ECMWF, a material difference for this time of year. The ECMWF's warmer pattern also generates slightly more cooling demand (32.5 wCDDs vs GFS's 28.5 wCDDs), further weakening its net demand signal.

Model Agreement & Caveats

Confidence in this forecast is low due to significant model disagreement and instability.

• Convergence: The models show poor agreement, reflected in a weighted_mean_abs_hdd_diff_by_day of 3.95. This indicates a persistent and meaningful daily difference in the temperature outlooks.
• Instability: The ECMWF's large run-over-run shift warmer is a major red flag, suggesting its solution is unstable. Until the models begin to converge, traders should treat both outcomes with caution. The GFS, in contrast, was more stable, adding only 6.5 weighted HDDs since its prior run.
• Source Limitations: This analysis is based on a limited set of demand-weighted hubs from Open-Meteo and serves as a proxy for the full U.S. demand picture.