Polar vortex reverses direction, setting record‑early stratospheric warming

The polar vortex has switched from its usual westerly flow to easterly winds, marking the earliest major sudden stratospheric warming (SSW) on record.

Scientists say the reversal, observed high above the Arctic, indicates a weakening and shift in the vortex’s position. Normally, strong westerly winds keep cold air trapped over the North Pole, but recent weeks have seen the vortex weaken and move, allowing easterly winds to dominate.

Such a major SSW is typically linked with colder, drier weather in the UK and can influence the jet stream, potentially bringing northerly or easterly flows that carry Arctic air. However, experts caution that an SSW does not automatically produce cold or snowy conditions, and any impact on weather will take time to develop.

The previous earliest SSW on record occurred on 28 November in both 1969 and 2025. This autumnal event is unprecedented in modern observations, leaving scientists uncertain about its likely effects in the coming weeks.

While similar disruptions have been associated with severe winter storms in North America – such as the February 2021 storm that reached Texas – those events happened in late winter when the Arctic is much colder. The early timing of this SSW means any chill spells may be muted.

Researchers also note that the world is moving toward a peak El Niño, a separate climate pattern that could further influence global weather, though its interaction with the current vortex change remains unclear.

Source: BBC News. Photo: Kees Koertshuis / Pexels.