The wind that circles the Arctic stratosphere is forecast to drop to 4.15 meters per second on November 3, according to NASA’s Ozone Watch data. The lowest value ever recorded for that date across the 1978-79 through 2025-26 seasons is 14.35 meters per second, so the forecast sits roughly 10 meters per second below the previous floor. A normal reading for the day would be about 26 meters per second.
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A reading that low is an early-winter oddity, not a cold-air guarantee. The polar vortex is a band of strong west-to-east winds high above the pole, and when it slows sharply, the cold that was bottled up can spill south. Whether anyone on the ground feels it depends on where the ridges and troughs set up weeks later, and early November is when the Arctic holds the least cold air of the whole winter.
The numbers behind the forecast
The Watchers’ Rishav Kothari laid out the October 26 run of the 10 hectopascal wind at 60 degrees north: 22.12 meters per second on October 25, about 12.04 on October 31, 9.15 on November 1 and 4.15 on November 3, against a November 3 average of 25.97. The 14.35 figure he used as the record low is the minimum in the dataset for that date, a climatological floor rather than an observed storm, which is why forecast values under it make news.
The underlying series is public. The NASA Ozone Watch file read on November 1 had already revised the November 3 value down to 2.57 meters per second and listed -0.62 for November 5, which would mean the westerly winds flipping to easterly. That flip is the definition of a major sudden stratospheric warming, and the file’s forecast column runs only a few days, so the later numbers will keep changing.
Reversal odds and the early-record claim
Whether the winds actually reverse is where forecasters part ways. Andrej Flis of severe-weather.eu cited ensemble reversal odds of 96 percent for the European model, 71 percent for the American GEFS and 37 percent for the AIFS machine-learning system, centered around November 4. He wrote that a reversal would be the earliest sudden stratospheric warming on record, beating a November 28 mark by at least three weeks.
The Weather Network’s Tyler Hamilton was more careful. He wrote that a reversal is not a given, that it remains unlikely, and that models had not settled on a final outcome, while noting that upward-moving waves from the lower atmosphere appear to be feeding energy into the vortex. His read was that the event is building from the ground up, driven by pressure ridges near the surface, and that a disruption in January or February would matter far more than one in November.
The measurement itself is narrow. NASA’s series tracks the zonal-mean zonal wind, meaning the west-to-east wind averaged around the full circle of 60 degrees north latitude, at the 10 hectopascal level, roughly 30 kilometers up. The Weather Network pointed to an unusual disturbance at about that altitude over the North Pole as the first complication, and Environment and Climate Change Canada describes the vortex as a band of strong west-to-east stratospheric winds that sits well above the weather people live in.
Flis added that stratospheric temperatures at 10 hectopascals could climb to almost 22 degrees Celsius above normal around ten days out, and that the ECMWF seasonal forecast shows a polar vortex slowdown beginning in January 2027, about a month earlier than in past analog winters. Neither number is a surface forecast, and both depend on model runs that will be replaced several times before the event arrives.
Probabilities differ by system: the European ensemble leaned heavily toward reversal, while the machine-learning AIFS gave it barely better than one chance in three.
What it would and would not do to North American weather
Forecasters agree that a weak vortex does not map directly onto a cold snap. Flis stressed that his temperature maps were single-run examples, not fixed outcomes, and they showed the eastern half of the United States turning colder than normal around November 7 and 8 while eastern Canada ran very mild. The Weather Network kept its seasonal outlook for a milder start to winter across much of Canada, and said the displaced cold could just as easily head to Europe or Asia.
The El Niño backdrop complicates things further. NOAA’s Climate Prediction Center reported on October 8 that the Niño-3.4 index stood at +2.1 degrees Celsius and that a strong-to-very-strong event was likely through January-March 2027. FOX Weather’s forecasters wrote that most long-range models show a major vortex disruption starting in the second week of November, and that El Niño tends to raise the odds of a weakened vortex, though usually later in winter.
The test comes within days. If the NASA series bottoms out near zero on schedule and the forecast column for November 5 holds negative, the stratosphere will have broken its own early-season record by a wide margin. What reaches the surface after that is the open question, and the first colder-than-normal signals in the U.S. maps Flis posted are dated November 7.
This article was produced with the assistance of AI and reviewed by Morning Overview editors prior to publication.
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