ALABAMA — A Sudden Stratospheric Warming event is underway high above the North Pole, and it is expected to collapse the polar vortex earlier than ever recorded. All 50 European forecast scenarios show the breakdown happening by November 12, well ahead of the previous record of November 28. The event does not mean cold weather arrives in Alabama next week, but it does raise the odds of real cold from Thanksgiving into December.
Polar Vortex Acts Like a Fence Holding Arctic Air Over the Pole
About 20 miles above the North Pole, a strong ring of wind circles the Arctic, acting like a fence that keeps the coldest air on Earth bottled up over the polar region. This circulation is known as the polar vortex.
During a Sudden Stratospheric Warming, the air high above the pole warms sharply over just a few days. When that happens, the circling winds can weaken or even reverse, allowing the fence to break down and the vortex to stretch or split apart.
Vortex Split Arriving Earlier Than Ever Recorded
The latest data already shows the winds at 10 hectopascals near 60 degrees north running slightly reversed at about negative 0.8 meters per second. The vortex appears split into two separate centers, with one lobe over northern Canada and another over Siberia and northern Europe.
Next week, the collapse is expected to become complete, marking the earliest such event on record. Every one of the 50 European ensemble scenarios shows the breakdown by November 12, more than two weeks ahead of the previous record date.
Alabama Stays Mild for the Next Two Weeks
The polar vortex collapse does not mean cold air will arrive in Alabama right away. The next two weeks are expected to stay mild across the state, with no major Arctic outbreak in the near-term forecast.
Effects from a stratospheric warming event usually take time to work down into the lower atmosphere. With the fence down, Arctic air can spill south in the weeks that follow, and for Alabama the window to watch runs from Thanksgiving into December.
Super El Niño Storm Track Adds a December Wildcard
A strong El Niño pattern is also in place, which typically brings a wet and busy storm track across the southern United States. That active pattern means more frequent systems moving through Alabama during late fall and winter.
Cold air arriving at the same time as that Gulf moisture is the December combination to watch closely. There is no snow forecast at this time, only better-than-normal odds that December brings colder weather, and the next four to six months could be unusually interesting across the state.
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