According to NOAA, the U.S. gas population weight HDD total for DEC/JAN/FEB 2024-25 was 2637 HDD ranking just-finished winter as the coldest since 2013-14 and 11th coldest of this century. Interestingly, the top 10 coldest U.S. winter seasons of this century all occurred by winter of 2013-14.

Today’s 12Z GFS forecast is the first to show a sprawling colder and stormy look since stratospheric warming conditions were in the forecast. At midday, the 12Z GFS reveals an evolving central North America longwave trough. The polar vortex shifts from the coast of Northeast Canada to Hudson Bay.

Weekend forecasts maintain the stratospheric warming episode unfolding on the Eurasian side of the North Pole in the short-term and gradually extending across the polar region in the 15-day outlook. The Graph Cast 500 MB anomaly forecast indicates a polar vortex pattern forms on the Northeast Canada Coast with moderate intensity troughs located in Alaska and the West U.S.

The daily Nino12 SSTA roars to +1.36C and is nearly 2C warmer than 30 days ago. The 2024-45 La Nina appears short-lived! The much warmer change is driven by effects from a recent Madden Julian oscillation regime.