The latest 10-day trend presents a classic split in the UK’s late summer weather pattern.
The first half of the forecast period is dominated by high pressure, promising fine and settled conditions for many. However, as we move into next week, the influence of tropical systems, particularly the remnants of Hurricane Erin, introduces increased uncertainty and the potential for a shift to more unsettled weather.
High pressure brings a fine weekend
As we head into the weekend, high pressure is firmly in control. This system is building in from both the north and the west, gradually extending across the UK. When high pressure dominates, the air tends to sink, suppressing cloud formation and leading to dry, settled conditions. Most areas can expect a fine weekend, with plenty of dry weather and light winds.
However, it won’t be entirely cloud-free. Old weather fronts attempting to push in from the west will introduce patches of cloud, particularly in western regions. This setup is often referred to as a “dirty high”, a high-pressure system that isn’t completely clear, but still manages to keep most areas dry.
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Cooler mornings, warmer afternoons
The arrival of high pressure also brings a change in air mass, with cooler air spreading across the country. This will be particularly noticeable in the mornings, especially in rural areas where temperatures could dip into single digits. Commuters may feel a fresher start to the day, but as the sun rises, temperatures will begin to climb.
By Saturday, southern parts of the UK could see highs of 24°C to 25°C, especially where sunshine breaks through. Sunday looks even warmer, with widespread low 20s across the UK and potentially 26°C in the south. Northern Scotland may remain in the high teens, but overall, temperatures will be close to or slightly above average for this time of year.
Bank holiday outlook
For many, the upcoming weekend is a bank holiday, although not in Scotland. The high-pressure system is expected to remain in place through Monday, bringing another largely dry and fine day. However, there is a caveat: showers cannot be entirely ruled out, particularly in the far southwest. These may be linked to the evolving situation in the Atlantic, where Hurricane Erin is undergoing a transformation.
Hurricane Erin and the Atlantic setup
Currently located off the eastern coast of the United States, Hurricane Erin is tracking northwards over cooler waters. As it does so, it will lose its tropical characteristics and transition into a more typical area of low pressure, a process known as extra-tropical transition.
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This change is significant because it alters how the system interacts with the jet stream. Initially, Erin’s movement northwards creates a strong temperature contrast between warm tropical air and cooler northern air, which energises the jet stream. As Erin transitions, the temperature contrast shifts to the southern side of the system, potentially intensifying the jet stream in that region.
This interaction is complex and introduces uncertainty into the forecast. The system may intensify as it crosses the jet stream, but it’s also contributing to the jet stream’s behaviour. It’s a dynamic scenario that forecasters are monitoring closely.
Model agreement and forecast confidence
Most computer models now agree that the jet stream will dip southwards, allowing the low-pressure system to move into the mid-Atlantic. Although, by Monday, Erin, or what remains of it, will still be well away from the UK. It's position and movement are crucial to determining the weather for the rest of the week.
Three key models, the UK Met Office model, the European model, and the American GFS model, are showing similar outcomes for five days ahead. All place the system in roughly the same area, suggesting a degree of confidence in the general setup.
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Beyond the deterministic models, ensemble forecasts provide a broader view. These run the same model multiple times with slightly different initial conditions to explore a range of possible outcomes. The ensemble forecasts for Monday show various scenarios, with some placing low pressure close to the southwest of the UK and others further afield. This spread highlights the uncertainty and the need to monitor developments closely.
The role of the jet stream
The jet stream plays a pivotal role in shaping the UK’s weather. At present, it’s relatively weak and meandering, but Erin’s interaction could reinvigorate it. As the system moves northwards and transitions, it may create a more active jet stream to the south, influencing the track and intensity of subsequent weather systems.
This setup means that while the UK won’t be directly impacted by a hurricane, the remnants of Erin could still affect our weather. The system is expected to bring tropical air and moisture, contributing to cloud formation and rainfall. The exact timing and extent of these impacts remain uncertain, but the trend points towards a shift to more unsettled conditions.
Midweek transition to unsettled weather
As we move into Tuesday, the most likely scenario is for low pressure to sit to the west of the UK or edge closer to our shores. By Wednesday, Thursday, and Friday, low pressure is expected to be either just offshore or across southern parts of the country.
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Low pressure systems are associated with rising air, which promotes cloud development and rainfall. This means an increased likelihood of showers and longer spells of rain, particularly in southern and western areas. For those hoping for continued dry weather, this may be disappointing, especially as it coincides with the final week of school holidays for many in England and Wales.
Temperature trends and tropical influence
Despite the increased chance of rain, temperatures are likely to remain warm. The incoming low-pressure systems are expected to draw air from the southwest, potentially bringing tropical maritime air into the UK. This means that even with cloud and rain, temperatures could stay above average.
Whether the moisture and warmth come directly from Erin or another Atlantic system, the influence of tropical air is a key factor. Sea surface temperatures remain relatively high, and this can help maintain warmth in the air masses reaching the UK.
Forecast uncertainty and what to watch
The main source of uncertainty in the forecast is the position and evolution of Erin. As it transitions and interacts with the jet stream, it could influence the track and intensity of subsequent systems.
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There has been a trend in the past 24 hours towards a more northerly track, which could bring the system closer to the UK. However, its slow movement and the complex jet stream interaction mean that confidence remains limited.
Forecasters will be watching the ensemble spread, the jet stream behaviour, and the tropical transition closely over the coming days. These factors will determine how quickly the weather changes and how unsettled it becomes.
While the UK won’t be hit by a hurricane, the influence of tropical systems is still significant. The interaction with the jet stream, the position of low pressure, and the source of incoming air masses will all shape the forecast.
Keep up to date with weather warnings, and you can find the latest forecast on our website, on YouTube, by following us on X and Facebook, as well as on our mobile app which is available for iPhone from the App store and for Android from the Google Play store.
