As autumn settles in across the Northern Hemisphere, something unusual is happening and it could shape the weather Europeans experience in the weeks ahead.The stratospheric polar vortex over the Northern Hemisphere is facing an unusually early weakening, with forecast models suggesting a significant disruption within the next 10 days, at a time of year when it would normally be strengthening.
A major sudden stratospheric warming (SSW) is possible, which could influence weather patterns in the weeks that follow. Forecasters say it may increase the likelihood of persistent high-pressure areas across the mid-latitudes, with colder conditions developing weeks later.
What is the polar vortex? The polar vortex is a large area of low pressure and cold air high above the Arctic. It weakens in summer, then strengthens through autumn and into winter. Its strong anticlockwise circulation helps contain the coldest air near the pole, although disturbances can allow colder air to spill southwards into the mid-latitudes.
An SSW occurs when temperatures high in the stratosphere rise rapidly, often by as much as 50C in just a few days. The surge is associated with a dramatic weakening, or even a reversal, of the strong westerly winds surrounding the vortex, disrupting its circulation. Current forecast models strongly favour a significant weakening of the vortex. However, the complete reversal of the winds required for a major SSW remains uncertain.
The effects of such an event typically take time to reach the surface, and forecasters stress that Europeans should not expect an immediate plunge in temperatures. The likelihood of colder, more settled conditions across northern Europe could increase, but a spell of severe cold appears unlikely over the next two to three weeks. Any more pronounced chill would be a question for early winter.
Forecasters will be watching closely over the coming days to see whether the vortex merely weakens or breaks down altogether.
Disclaimer : This story is auto aggregated by a computer programme and has not been created or edited by DOWNTHENEWS. Publisher: deccanchronicle.com
