Earliest Polar Vortex Breakdown on Record Could Arrive This Week, Scientists Say

Forecasters are watching for what could be the earliest polar vortex breakdown on record, with models pointing to a reversal of stratospheric winds as early as Nov. 4 or 5 — roughly three weeks ahead of the previous earliest seasonal disruption, which typically hasn't occurred before late November.

Judah Cohen, a climate scientist at MIT who tracks the polar vortex closely, called it "the largest, earliest disruption of the polar vortex on record" and said the vortex is already showing signs of becoming unusually weak and stretched. "[It's] one of the most, if not the most surprising events or behaviors I have ever witnessed from the polar vortex," he said.

A disrupted polar vortex can send cold air spilling south into North America, Europe and Asia in the weeks that follow, though the exact timing and severity of any resulting cold snap remain uncertain this far out — several forecasters stressed there is no confirmed winter-storm threat yet to major airports or travel corridors. A weakened vortex is a risk factor for a colder-than-average winter, not a guarantee of one, and its effects on any single region can take weeks to materialize after the stratospheric event itself.