Forecasters point to 10-day window for early polar vortex break

Weather models indicate the polar vortex over the northern hemisphere may weaken during the next ten days, a period when it typically gains strength. This early disruption could alter winter patterns across Europe.

Forecasters identify a potential sudden stratospheric warming event as the driver. Such events involve rapid temperature spikes in the upper atmosphere, sometimes reaching 50C within days. This heat weakens or reverses the westerly winds that usually contain Arctic cold air near the pole.

The earliest recorded major warming event occurred on November 28, 1968. Current computer simulations strongly favor a significant weakening of the vortex, though a full wind reversal remains uncertain. If the vortex weakens, persistent high pressure areas may form in mid-latitudes, leading to colder conditions weeks later.

Northern Europe faces a higher chance of settled, colder weather in early winter. However, severe cold spells are unlikely in the next two to three weeks. The disruption marks an early-season shift that could influence the remainder of the winter.

In the immediate term, a low pressure system deepened in the Mediterranean last week. It will bring heavy rain and strong winds to central and southern Italy on Monday. Authorities have issued warnings for these regions as the system approaches.

More than 100mm of rain is forecast to fall in 24 hours on higher ground in southern Italy. The weather system will then move eastward across the Ionian Sea toward Greece. Greece is currently recovering from exceptionally wet conditions experienced last week.