GFS vs ECMWF Demand-Hub Outlook: 2026-06-26 00Z

Executive Summary

The 15-day outlook signals a period of robust cooling demand, with both GFS and ECMWF models forecasting significant, nearly identical national cooling loads (230.0 and 230.8 weighted CDDs, respectively). However, this strong top-line agreement masks material regional differences, with the GFS showing more heat in the high-demand Midwest and South Central hubs while the ECMWF concentrates intense heat along the East Coast. The GFS trended significantly hotter in this cycle (+29.7 weighted CDDs), bringing it into close alignment with the more stable ECMWF forecast.

Hub-Level Weather

The national forecast is primarily driven by the Midwest (Chicago, 35% weight) and the East (New York City, 30% weight).

• Midwest (Chicago): The models show a key divergence in the 10-15 day period. While the ECMWF is warmer in the first week, the GFS is substantially hotter from July 5th onward, resulting in a slightly higher cumulative total (GFS: 247.5 CDDs, ECMWF: 238.9 CDDs).
• East (New York City & Boston): The ECMWF is consistently hotter in the East. The difference is most pronounced in Boston, where the ECMWF forecasts nearly double the cooling demand of the GFS (132.7 CDDs vs. 69.2 CDDs), driven by a major heatwave signal around July 1-3 and July 7-8. A similar, though less extreme, pattern exists for New York City (ECMWF: 210.5 CDDs, GFS: 198.7 CDDs).
• South (Houston & Atlanta): The GFS projects a hotter outcome for the southern hubs. In Houston (15% weight), the GFS forecasts 329.6 CDDs versus the ECMWF's 300.0 CDDs, showing sustained, stronger heat through most of the 15-day period.

Demand Implications (Natural Gas)

The strong cooling demand profile across all hubs implies sustained, above-normal natural gas consumption from the power generation sector (power burn) for the next two weeks.

• The GFS solution, with higher CDD totals in the high-consumption Midwest and Texas markets, may point to a slightly more bullish national demand scenario than the ECMWF.
• The ECMWF's forecast for intense heat in the Northeast, particularly Boston, could lead to acute regional price volatility and grid stress, though its national demand impact is moderated by the region's lower demand weight (10%).
• The significant addition of demand in the GFS model this cycle (+29.7 weighted CDDs) strengthens the conviction in a hot pattern emerging, as it moves toward the ECMWF's previously hotter baseline.

Model Agreement & Caveats

Confidence in the overall warm theme is high, reflected by an excellent convergence score of 0.985. The models are in strong agreement on the national demand total.

• Caveat: This high-level agreement conceals significant regional disagreements, particularly in the Northeast and Midwest beyond day 7. As is typical, forecast reliability diminishes in the latter half of the 15-day period.
• Source: This analysis is based on GFS and ECMWF model data from Open-Meteo, using a specific, weighted set of demand hubs. It represents a proxy for national demand and is not a comprehensive CONUS-wide assessment.