Global model forecasts of NH 500-hPa geo. height exhibited a noticeable decrease in skill for F120 forecasts valid 12/28/23–1/6/24. All global models shown had ACC scores <0.9 for ≥7 days! Question is: What caused this noticeable decrease in skill? Tough pattern? Something else? pic.twitter.com/dKdwkE31wF

— Dr. Alicia M Bentley (@AliciaMBentley) January 12, 2024