# Polar vortex reversal earliest on record but snow uncertain

> Arctic winds have reversed direction in an unprecedented autumn event, but whether it brings snow to the UK remains unclear.
- Title: Polar vortex reversal earliest on record but snow uncertain
- Summary: Arctic winds have reversed direction in an unprecedented autumn event, but whether it brings snow to the UK remains unclear.
- Keywords: polar vortex, sudden stratospheric warming, arctic, uk weather, snow, el niño, jet stream, north america, BBC News
- Source: BBC News — https://bbc.co.uk/weather/articles/cwdd8dl7830go
- Read time: 2 min
- Topics: polar vortex, sudden stratospheric warming, arctic, uk weather, snow, el niño, jet stream, north america, news, world
## Polar winds reverse in record early event
The spiralling winds of the polar vortex high above the Arctic have reversed direction, marking the earliest major sudden stratospheric warming on record.
## What is sudden stratospheric warming?
Sudden stratospheric warming occurs when a rapid temperature rise happens high in the stratosphere, roughly ten to thirty miles above Earth's surface, weakening the polar vortex winds.
## How it filters down to affect weather
Changes in the stratosphere slowly filter lower in the atmosphere, altering the position of the jet stream which drives what type of weather we experience on the ground.
## Historical link to UK cold and snow
Major sudden stratospheric warming events have historically increased the chance of drier and colder weather in the UK with northerly or easterly winds bringing Arctic air and boosting snow possibility.
## But this event is unprecedented
The previous earliest sudden stratospheric warming on record happened on twenty-eight November in both nineteen sixty-nine and twenty twenty-five. This autumn occurrence is unprecedented in modern observations.
## Snow outcome remains highly uncertain
A sudden stratospheric warming does not automatically lead to cold or snowy weather and any influence would take time to develop. There are very few historical examples of early season major events to compare.
## Global impacts possible but uncertain
Because the stratospheric polar vortex operates at a global scale, disruptions can increase the possibility of cold weather, ice and snow in North America. But impacts remain very uncertain.
## El Niño adds another layer of complexity
The UK is heading towards the expected peak of the strongest El Niño on record. El Niño can increase the likelihood of disruption to the stratospheric polar vortex, but any link remains unclear.
## Forecasting faces multiple uncertainties
No two El Niños are the same. Longer-range forecasting can give probabilities of certain weather patterns but interactions between the atmosphere and oceans are complex, compounded by human-induced climate change.
## Key takeaway

The polar vortex has reversed direction in the earliest major sudden stratospheric warming on record, but experts say any impact on UK snow remains highly uncertain.