GFS vs ECMWF Demand-Hub Outlook: 2026-06-16 00Z

Executive Summary

The 15-day outlook shows remarkable agreement on the national demand-weighted cooling load (GFS 135.1 TCDDs vs. ECMWF 134.8 TCDDs), implying a similar level of above-normal power burn. However, this top-line agreement conceals significant regional disagreements, with the GFS forecasting intense heat in the South while the ECMWF is materially warmer in the Midwest and East. The GFS trended substantially hotter versus its prior run (+29.2 TCDDs), adding a bullish tint to the forecast despite the model divergence.

Hub-Level Weather

The primary drivers of the national forecast are the major hubs in the Midwest and East, but the largest model disagreements are in the Midwest and South.

• Midwest (Chicago, 35% weight): This is the main point of contention. The ECMWF is significantly warmer, forecasting 72.4 CDDs versus the GFS's 47.0 CDDs. The GFS is cool enough to generate 10.7 HDDs, while the ECMWF forecasts only 4.1 HDDs.
• South (Houston & Atlanta, 25% combined weight): The models flip their bias in the South, where the GFS is drastically hotter.
  • In Houston, the GFS forecasts 303.6 CDDs, a full 64.3 CDDs more than the ECMWF's 239.3 CDDs.
  • In Atlanta, the difference is even more stark, with the GFS at 230.1 CDDs vs. the ECMWF's 146.4 CDDs.
• East (New York City, 30% weight): The ECMWF is moderately warmer, projecting 169.3 CDDs compared to the GFS's 148.0 CDDs. The largest daily differences emerge in the 6-10 day period (June 22-24).

Demand Implications (Natural Gas)

The overall forecast points to robust cooling demand and associated power generation gas burn for the latter half of June.

• National Demand: Both models project a similar level of national cooling demand, which would support prices. The near-term (1-5 days) is fairly well-agreed upon, but risk and uncertainty grow substantially in the medium-to-long range.
• Regional Demand & Basis Risk: The key takeaway for gas markets is the regional risk. The GFS scenario would heavily pressure grids in ERCOT and the Southeast. Conversely, the ECMWF solution implies stronger demand pulls from the PJM and MISO power markets.
• Run-over-Run Shift: The GFS added a significant 29.2 weighted CDDs compared to its previous cycle. This is a strong bullish trend. The ECMWF was far more stable, adding only 4.0 weighted CDDs, lending it more consistency.

Model Agreement & Caveats

Confidence in the forecast is moderate in the near term but low beyond day 7 due to sharp regional disagreements.

• Convergence: The national convergence_score of 0.7888 is misleadingly high. While the final weighted numbers are close, the underlying regional forecasts are highly divergent, suggesting low confidence in the specific evolution of the pattern. The models achieve the same result via completely different means.
• Caveats: The significant hotter trend in the 00Z GFS warrants caution, as it could be an outlier run that reverts in future cycles. The forecast beyond 10 days should be viewed with skepticism until the models show better agreement on the placement and intensity of key weather features.
• Source: This analysis is based on a specific set of demand hubs and weights using publicly available data from Open-Meteo's API. It is an illustrative, not exhaustive, view of total U.S. natural gas demand.