The Northern Hemisphere’s polar vortex could undergo an unusually early disruption in November 2026, with weather models forecasting a sharp weakening of stratospheric winds and a possible split into two separate circulation centers.
The disruption could develop within the next 10 days, at a time of year when the polar vortex would normally be strengthening ahead of winter. Some forecasts indicate that winds surrounding the vortex could reverse direction, potentially triggering a major sudden stratospheric warming (SSW) event.
- Forecast models indicate the Northern Hemisphere polar vortex could weaken sharply or split into two separate cores during early November 2026, potentially triggering the earliest major sudden stratospheric warming on record.
- A reversal of stratospheric winds could alter atmospheric circulation, increasing the likelihood of colder conditions across northern Europe and the eastern United States in the following weeks.
- A developing Super El Niño adds uncertainty to the winter outlook, while longer-range forecasts suggest another potentially stronger polar vortex disruption during winter 2026/2027.
If a major SSW occurs in early November, it would be the earliest recorded since observations began in 1958. The previous earliest event occurred on November 28, 1968.
Forecast confidence is higher for substantial weakening than for the complete wind reversal required to classify the event as a major SSW.
The potential disruption could influence weather patterns across Europe and North America later in November and into early winter, although an immediate outbreak of severe cold is considered unlikely.
Polar vortex forecasts show possible split in November 2026
The polar vortex is a large circulation of cold air and low pressure centered over the polar regions. Its strongest upper-level component develops in the stratosphere, which extends to altitudes of approximately 50 km above Earth’s surface.
The system weakens during summer and typically strengthens through autumn as temperatures fall across the Arctic.
Strong westerly winds circulating anticlockwise around the Northern Hemisphere polar vortex help contain the coldest air near the pole. When the circulation weakens or becomes displaced, atmospheric patterns can become more favorable for Arctic air moving into lower latitudes.
The polar vortex has interconnected stratospheric and tropospheric components. The troposphere is the lower atmospheric layer where most weather occurs, while the stratosphere lies above it.
Although these layers interact, changes in the stratospheric vortex do not always produce corresponding changes in surface weather.
Current model projections indicate a possible division of the stratospheric circulation into two cold cores, one over Siberia and another over North America, with higher pressure developing around the Aleutian region.
Such a configuration would represent a substantial departure from the stronger, more consolidated vortex normally expected during early November.
Sudden stratospheric warming could set an early-season record
A sudden stratospheric warming occurs when temperatures in the polar stratosphere rise rapidly, sometimes increasing by as much as 50°C within several days.
These events are associated with significant weakening of the westerly winds surrounding the polar vortex. During a major SSW, the prevailing winds at the relevant stratospheric level reverse direction.
The circulation can become displaced from the pole or split into separate centers. Forecast models increasingly favor a significant weakening during early November, but uncertainty remains over whether the wind reversal necessary for a major event will occur.
An early-November reversal would precede the November 28, 1968 record by more than three weeks, making it an exceptionally early event in the observational record.
The timing also makes its potential consequences difficult to assess. Most major sudden stratospheric warming events occur later in winter, when atmospheric circulation and the relationship between the stratosphere and troposphere can differ considerably from autumn conditions.
Polar vortex weakening could bring colder weather to Europe and the US
A disrupted polar vortex can alter atmospheric circulation over the following weeks, potentially increasing the persistence of high-pressure systems across northern and middle latitudes. These pressure patterns can influence the movement of colder Arctic air into populated regions of Europe and North America.
Current forecasts suggest cooler temperature trends could emerge across parts of northern Europe and the eastern United States as the projected disruption develops.
Colder, more settled conditions may become more likely across northern Europe later in November, although widespread severe cold is not currently expected during the next two to three weeks.
The timing and geographical distribution of any temperature changes remain uncertain because the effects of stratospheric disturbances can take several weeks to influence lower atmospheric circulation.
The developing Super El Niño is another factor affecting the broader atmospheric pattern, complicating forecasts of how an unusually early vortex disruption might influence regional weather.
Longer-range projections also indicate the possibility of a stronger disturbance during the middle of winter 2026/2027. Those forecasts remain preliminary and do not establish that another major warming event will occur.
Mediterranean storms bring heavy rain to Italy and Greece
Separately, a low-pressure system that intensified over the Mediterranean Sea last week is expected to bring heavy rainfall and strong winds to central and southern Italy on Monday, November 2.
Weather warnings have been issued for affected areas, with rainfall totals exceeding 100 mm forecast across higher elevations in southern Italy within 24 hours.
The system is expected to move eastward across the Ionian Sea before reaching Greece.
Greece is still recovering from exceptionally wet and unsettled conditions during the previous week, leaving parts of the country exposed to additional heavy rainfall.
The Mediterranean disturbance is a more immediate weather threat than the projected stratospheric changes, whose potential effects on European and North American temperatures are expected to develop over a longer period.
Forecast models will continue to determine whether the early-November polar vortex weakening progresses into a major sudden stratospheric warming event and whether its effects extend into the lower atmosphere during the opening weeks of winter.
