This week’s persistent high-pressure system is still currently dominating the UK’s weather, resulting in anticyclonic gloom, but what do the latest forecasts suggest for the coming days and weeks?
In this week’s Deep Dive, we’ll examine why the weather has been so settled, why cloud has been so stubborn, and how the pattern is set to change as we move towards the end of October.
A remarkably sunny year - until now
It is worth starting with some perspective. While this week has felt dull and grey for many, 2025 has so far been a remarkably sunny year. A review of monthly sunshine records over the past 10 years shows that, with the exception of February, every month since March has been sunnier than average. Spring 2025 was the sunniest on record, and even September, despite frequent rainfall, was brighter than usual.
This run of seven consecutive sunnier-than-average months is highly unusual in over a century of UK records, stretching back to 1910. However, October looks set to break this streak, with widespread cloud and gloom reminiscent of last autumn and, in particular, last December, a notably dull month.
Why is the high pressure stuck?
The key to this week’s weather lies in the position and persistence of a large area of high pressure, anchored over the UK. This “blocking high” has been responsible for the settled conditions, but also for trapping a layer of low cloud over much of the country. To understand why the high is so persistent, we need to look at the broader atmospheric pattern, particularly the behaviour of the jet stream.
High pressure remains in charge through this week, bringing anticyclonic gloom for many ☁️
— Met Office (@metoffice) October 14, 2025
However, a change is on the way over the weekend with low pressure retuning, bringing wetter and windier conditions from the west ☔ pic.twitter.com/NTdjOFFfEm
Meteorologists use the concept of planetary-scale “waves” in the jet stream to describe the meandering path of high and low-pressure systems around the globe. This week, the jet stream has adopted a “wave number five” pattern, meaning there are five major ridges and troughs circling the northern hemisphere.
This pattern is significant because it tends to be more amplified and persistent than the more typical “wave number three” pattern. When the frequency of these atmospheric waves matches the natural resonance set by the continents and mountain ranges (such as the Rockies), the highs and lows become “stuck”, leading to prolonged spells of similar weather in the same locations.
The science behind the gloom: Low cloud and temperature inversions
While high pressure often brings fine weather, this week has been dominated by anti-cyclonic gloom, a stubborn layer of low cloud that has proved difficult to shift. The explanation lies in the vertical structure of the atmosphere. Upper air observations, including weather balloon data, show a classic temperature inversion in place: a layer of warmer, drier air sits above a shallow layer of cooler, moist air near the surface. This inversion acts as a lid, trapping cloud and moisture below.
For most of the UK, this has meant persistent grey skies. However, in areas of higher ground, such as the Pennines, Scottish mountains, and parts of North Wales, summits have poked above the cloud, basking in sunshine and exceptionally dry air. For example, on Great Dun fell in the Pennines (847 metres above sea level), Sunday saw a maximum temperature of 20.4°C and a dew point of around -18 to -19°C, resulting in a relative humidity of just 4%, drier than many of the world’s deserts. This was also the warmest place in the UK on that day.
READ MORE: What is Anticyclonic gloom?
Satellite imagery from Monday afternoon confirms that most of the UK was blanketed by low cloud, with breaks mainly over higher ground. The movement of air over hills and mountains helps to mix the cloud into drier air above, creating gaps and sunny spells in these regions. However, for most, the cloud has been slow to clear, and computer models have struggled to predict exactly where and when breaks would occur.
The thinness and fickleness of the cloud layer, combined with light winds and subtle variations in surface moisture, make this a particularly challenging situation for forecasters.
Why does the sun make a difference?
One of the reasons for the persistence of low cloud at this time of year is the relative weakness of the sun. In spring and summer, stronger solar heating can provide enough buoyancy to break through the inversion, lifting the cloud into the drier air above and allowing it to dissipate. In autumn, however, the sun is too weak to overcome the inversion, so the cloud remains trapped.
This is why similar high-pressure patterns can produce very different weather depending on the season: sunny and warm in spring, but grey and gloomy in autumn and winter. The subtlety of the atmospheric conditions this week has made forecasting particularly difficult. Small differences in temperature, humidity, or wind direction can determine whether a location experiences sunshine or remains under cloud.
A global perspective: Planetary resonance and the Jetstream
Returning to the broader picture, the persistence of high pressure over the UK is linked to the current configuration of the jet stream. The “wave number five” pattern, with its amplified ridges and troughs, has created a situation where highs and lows are locked in place. This is then reinforced by the natural geography of the northern hemisphere, with mountain ranges and continents helping to anchor the pattern.
However, the atmosphere is not static. Disturbances, such as deep lows or thunderstorms in the Pacific, can disrupt the Jetstream, causing the pattern to shift. This week, meteorologists have been tracking a disturbance in the Pacific that is expected to break the current pattern, leading to significant changes in the UK’s weather as we move into next week.
The forecast: Change is on the way
So, what does the latest guidance suggest for the days ahead? The high pressure is expected to remain in place through Friday, with low cloud continuing to affect many areas. By Saturday, the high will begin to migrate slowly eastwards, allowing a weather front to approach from the Atlantic. This will bring a change in wind direction and, for many, a return of sunshine as the anticyclonic gloom starts to lift.
READ MORE: Specialist forecasts for a resilient future
However, it is not until Sunday that a more significant change is expected. A low-pressure system in the Atlantic will begin to break through, bringing outbreaks of rain, especially to western parts of the UK. Model guidance from both the Met Office and the European Centre for Medium-Range Weather Forecasts (ECMWF) shows some uncertainty in the exact track and timing of this low, but all simulations agree that a transition to more unsettled weather is likely.
Model uncertainty and ensemble forecasts
One of the key tools for forecasters is the use of ensemble models, multiple simulations with slightly different starting conditions. This approach helps to capture the range of possible outcomes and quantify uncertainty.
For Sunday and Monday, ensemble guidance shows a wide spread in the possible tracks of the initial low-pressure system, with scenarios ranging from the northwest of Scotland to the southwest of England. There are also differences in the depth and timing of the low, with some simulations bringing rain earlier or later, and some showing a deeper, more intense system than others.
Despite these uncertainties, the overall theme is clear: next week will be dominated by low pressure, with spells of rain slowly moving across the UK. The wettest conditions are likely in the west and south, but all areas can expect some rain. Compared to this week, next week will be much wetter than average, especially in the south and east, which are typically drier at this time of year.
Looking further ahead: The end of October
As we move towards the end of October, model guidance suggests a further transition. By the weekend of the 27th, low pressure is expected to shift eastwards, with higher pressure building to the west. This would bring a more north-westerly airflow, cooler temperatures, and a return to showery conditions. However, there is no sign of a significant cold spell; temperatures are expected to remain close to average for the time of year.
In summary, while high pressure has brought settled but gloomy conditions, the atmosphere is poised for change. As always, the interplay between global patterns, local geography, and seasonal variations makes for a fascinating, and sometimes unpredictable, forecast.
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