Stratospheric warming emerges over Siberia as calendar-winter arrives. The risk of arctic air generation at ground level increases dramatically in this region. In North America, the stratosphere is cold and supports anomalous warmth at ground level for Canada and the U.S. in 16 days. However, once we’re into January, ECMWF continues to indicate an emerging polar vortex which is steadily broadening and strengthening.

The persistent Madden Julian oscillation (MJO) and causal westerly wind burst (WWB) has created a scenario where latent heat release to the upper atmosphere and poleward via a Rossby Wave is causing forecast models to indicate a stratospheric warming event across Northeast Asia in the 11-15-day period increasing strength as day 15 arrives. The stratospheric warming event could trigger an arctic air mass formation across Eurasia late in December if this feature is well organized.

The 2024 North Atlantic basin tropical cyclone season ended on November 30. This year, the final tally on tropical cyclone activity was 18 tropical storms, 11 hurricanes, and 5 major hurricanes with an accumulated cyclone energy (ACE) index of 161.6. The above normal activity maintains the recent pattern (2016-24) of very active (and dangerous) tropical cyclone seasons.

Taking a look at the 11-15-day East U.S. temperature anomaly outlook reveals lingering cold when combining the GFS and ECM forecasts. However, AI models offer wildly different projections (colder or warmer). So...a look at climate diagnostics reveals what direction to rely.