30-Day Skill Scores of U.S. Medium-range Temperature Anomaly Forecasts

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Climate Impact Company U.S. Medium Range Report

Issued: Thursday August 14, 2025

Highlight: Preferred ECM ENS is hotter than AIFS ENS in the medium range.

Chart of the day: U.S. medium-range forecast skill scores.

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Discussion: U.S. medium range 2-meter temperature anomaly forecasts during the past 30 days were most efficient utilizing the new AIFS ENS and ECM ENS in both the 6-10-day and 11-15-day periods. The highly visible GFS forecast lags with second lowest skill scores. Other AI models (4Cast Net V2) also produced lower skill scores. The Canadian Ensemble (CMC ENS) has performed quite well this summer season.

Medium-range 6-10 Day Forecast Valid August 19-23, 2025 (24-hour change right)

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Discussion: ECM ENS is warmer in the Interior East with the heat core remaining over the Interior West although California is hotter. Machine learning model AIFS ENS is not as warm as ECM ENS in the East or California.

Medium-range 11-15 Day Forecast Valid August 24-28, 2025 (24-hour change right)

A map of the weather AI-generated content may be incorrect.A map of the united states AI-generated content may be incorrect.

Discussion: ECM ENS is reasonable with a cool air mass centered on Ontario to the Upper Midwest while anomalous heat continues in the West. The machine learning AIFS ENS is somewhat cooler and pushes the western heat into the Northwest States.

U.S. Medium-range Precipitation Forecast

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Discussion: Erin moves north-northeast staying away from the Atlantic Seaboard in the 6-10-day period. However, the frontal system booting Erin away from the coast brings wet weather to Virginia. The 11-15-day forecast is wet in the Southwest U.S. to the Continental Divide and a possible new tropical threat in the Caribbean Sea.

Days 16-20 Extended range Temperature Forecast valid August 29-September 2, 2025

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Discussion: The AI models are defeating dynamic forecasts in the 16-20-day period. The AI 4Cast Net V2 ECM ENS is cool on the West Coast and temperate East as meteorological summer ends. The CFS V2 most closely matches the AI-generated upper air pattern which implies a wet Mid-south U.S. forecast.