BIRMINGHAM, Ala. — The signal for a record-early Sudden Stratospheric Warming, or SSW, has grown stronger. Every one of the 50 European ensemble members now shows the polar vortex winds reversing by November 12. If it happens, it would be the earliest major stratospheric warming on record. For Alabama, nothing changes for the next two weeks, but the odds of cold air later in the season are rising.
All 50 Ensemble Members Now on Board
One day earlier, 48 of 50 European ensemble members showed the polar vortex winds reversing by November 11. The latest run has all 50 members showing the reversal by November 12. The winds are forecast to bottom out below zero around November 9.
Even the AI ensemble, which had been more skeptical, now has 33 of 50 members on board. Agreement this strong this far out is unusual. That is why forecasters are paying close attention to the signal.
Model Shows a Split Vortex
A forecast map of the stratosphere shows the polar vortex split into two pieces. One cold center sits over eastern Canada near Hudson Bay, while the other sits over the Arctic Ocean north of Russia. The map shows a gap of about 42 decameters between the two centers.
Winds around the vortex at 60 degrees north are shown at only about 1.7 meters per second, far weaker than normal. A strong vortex usually keeps the coldest air locked near the pole. A weak or split vortex makes it easier for that air to spill south.
Earliest Major Warming on Record
The current record for the earliest major stratospheric warming is November 28, set in both 1968 and 2025. A reversal around November 9 to 12 would break that mark by more than two weeks. Events like this usually happen later in winter, often in January or February…