Overview
- Observations reported by multiple outlets show the polar vortex in the stratosphere weakened and briefly reversed direction on Nov. 10–11, with upper‑level winds slowing from about 28 m/s to roughly 2 m/s and temperatures there near 10°C above normal.
- A short blast of Arctic air already brought colder‑than‑normal conditions to parts of North America and Europe this week, but forecasters say that snap is expected to be brief.
- Experts stress large uncertainty because downward coupling from the stratosphere to the troposphere typically takes 2–6 weeks and does not always occur, so any wider or longer‑lasting cold outbreaks are not guaranteed.
- A historically strong El Niño at the same time tends to favor warmer, wetter conditions across much of North America and therefore complicates or may blunt colder surface outcomes.
- Agencies and forecasting services are actively monitoring model guidance and observations and plan updated regional and seasonal outlooks later this month, with The Weather Network set to release a full winter forecast on Nov. 25.