# Weather tracker: Polar vortex collapse could chill North America and Eurasia

## Introduction

- A sudden stratospheric warming event is expected to develop over the next two weeks, leading to a rapid collapse of the polar vortex.
- This will be the second and probably final disruption of the polar vortex this winter in the northern hemisphere, the first having taken place earlier last month, which was associated with a severe cold spell across much of the eastern half of the US.

## Summary

- The next stratospheric event looks stronger than the previous one, and will probably weaken the jet stream pattern. This may allow a release of cold air from the polar regions to move southwards into North America or Eurasia, in turn increasing the risk of significant snow for some regions.
- Yosemite in California is already being affected by some severe late winter weather with more than a foot of snow expected at higher elevations in the first few days of March, accompanied by wind gusts of 50mph.
- Pakistan’s Islamabad, Kashmir, upper Khyber Pakhtunkhwa and upper Punjab are also facing strong winds, heavy rain and hill snow over the coming days. Travel disruption across these areas is expected and weather warnings have been issued.
- Slow-moving  will edge closer to the coast of Queensland in Australia over the next few days. While the weather system is expected to remain over the Coral Sea, it could move close to the east coast, bringing strong to gale-force winds on its south-western side with huge surf across the southern Great Barrier Reef islands and adjacent coastline. Severe weather warnings are in place with the potential for damaging wind gusts, which could also affect coastal north-east New South Wales.
- Also in the southern hemisphere, Cyclone Garance has led to at least four deaths on the French island territory of  in the Indian Ocean. Trees have been uprooted, streets inundated with flood water and cars washed away. Winds of up to 140mph (225km/h) were recorded in Piton Sainte-Rose on the east coast. About 160,000 people were left without power and 1,000 moved to temporary accommodation. A third of the island’s population have had no access to drinking water. In the west coast seaside resort of Saint Gilles, muddy water overflowed from a ravine and poured through the town centre, where excavators were needed to remove the mud.

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