Overview
- Meteorological models and agencies have identified an unusually early weakening or possible reversal of the Northern Hemisphere stratospheric polar vortex that could meet criteria for a major sudden stratospheric warming.
- Forecasters flagged this development earlier this week and say a full wind‑direction reversal in the upper stratosphere could occur within days to about ten days, which would make it the earliest major event in the satellite-era record if confirmed.
- Changes in the stratosphere do not produce immediate surface cold, and officials stress it typically takes roughly two to four weeks or more for any stratospheric signal to influence the jet stream and weather at ground level.
- A record-strong El Niño may be helping trigger the stratospheric disruption while simultaneously strengthening the Pacific jet, so seasonal outlooks from NOAA’s Climate Prediction Center still favor above-average temperatures across much of the northern United States.
- If the event propagates downward, regions of northern Europe and parts of the U.S. Midwest could see increased chances of colder, drier conditions in late November into December, which would affect heating demand, travel and snow risk depending on where jet-stream shifts land.