Storm Austen, the first named storm of the season, is expected to bring strong winds to parts of the UK from late Thursday and through Friday.
Storm Austen has been able to deepen rapidly because of its interaction with a powerful jet stream over the Atlantic. As the storm crosses the jet stream and enters the ‘left jet exit region,’ conditions high in the atmosphere support falling pressure at the surface, helping the low-pressure system strengthen rapidly.
How has the jet stream strengthened Storm Austen?
The jet stream is a band of strong winds high in the atmosphere which plays an important role in steering and developing weather systems. Within it, there can be sections where winds are stronger than in the surrounding flow. These are known as jet streaks.
Storm Austen is expected to interact with a developing jet streak over the Atlantic. Met Office forecasts indicate that a sharpening trough will engage with a baroclinic zone, an area where contrasting air masses help create a strong temperature gradient. This interaction supports the development of the jet streak and creates favourable conditions for the area of low pressure to deepen rapidly.
As Storm Austen crosses the jet stream, it will move into what meteorologists call the left jet exit region. This part of the jet stream can encourage air to rise and pressure to fall at the surface. The resulting atmospheric conditions will allow Storm Austen to strengthen quickly as it approaches northwest Europe.
Why is Storm Austen a ‘weather bomb’?
Current forecasts indicate that the pressure at the centre of Storm Austen could fall by at least 24 hectopascals within 24 hours. This rapid fall in pressure is known as explosive cyclogenesis and is sometimes described as a “weather bomb”.
The most intense features of a low-pressure system often develop during this period of rapid deepening. For Storm Austen, the fastest development is expected during Thursday as the system interacts with the jet stream and moves towards the UK and nearby parts of Europe.
By the time Austen moves closer to the UK, its rate of deepening is expected to slow as the storm reaches maturity. However, it will remain a deep and potentially impactful area of low pressure. Forecast models generally indicate that its central pressure will be between 970 and 980 hPa as it crosses the UK.
Where will the strongest winds occur?
Although confidence in the broad track of Storm Austen has increased, some uncertainty remains over its exact route. Small changes in the position of the low could affect where the strongest winds occur.
Gusts of 50 to 60 mph are possible for a time across northern France, with gusts potentially reaching 70 to 80 mph around exposed coasts and the Channel Islands. Across the UK, the strongest winds are currently expected in parts of southwest Britain from the early hours of Friday and into Friday morning.
An amber warning for wind has been issued for southwest England on Friday between 3am and 10am, while a yellow warning for wind covers a larger area of southwest and southern England and south Wales between 12am and 2pm.
Strong winds could damage buildings, bring down trees and cause disruption to power supplies and other utilities. Exposed roads and bridges may also be affected, while rough seas could disrupt maritime travel through the English Channel and create dangerous conditions around some beaches.
Met Office Deputy Chief Forecaster Chris Bulmer said: “Storm Austen is expected to bring a spell of impactful weather to parts of the UK from Thursday night and through Friday. While there remains some uncertainty in the exact track of the storm, there is increasing confidence in the potential for disruptive winds across parts of southwest England, which is why an Amber warning has been issued.
“Winds gusts could potentially reach 60-70 mph for a time, and these strong winds will be combined with spells of heavy rain. People in affected areas should keep up to date with the latest forecast and warnings as the event develops.”
What happens after Storm Austen?
A brief respite is expected early on Saturday before another spell of wet and windy weather potentially affects a similar area. This subsequent system is not currently expected to be named, but it reinforces the unsettled Atlantic pattern affecting northwest Europe.
Storm Austen demonstrates how closely the development of Atlantic storms can be tied to the jet stream. In this case, the combination of a sharpening trough, a jet streak and the storm’s movement into the left jet exit region will help transform an Atlantic low into a rapidly deepening and potentially disruptive system.
The precise track will remain important in determining which locations experience the strongest winds, so people are advised to keep up to date with the latest forecast and any warnings issued for their area.
READ MORE:
What does it take for a storm to be named?
Week ahead: First named storm of the season set to arrive on Friday
Weather bombs: What causes explosive cyclogenesis?
Are the UK’s seasons changing?
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