This week’s Met Office Deep Dive explores the dynamic weather patterns affecting the UK, highlighting the development of thunderstorms, the influence of the jet stream, and the phenomenon known as the Spanish Plume.
Recent weather patterns have been shaped by a shifting jet stream, which has allowed high pressure to build across much of the UK. This setup has led to rising temperatures and increasing humidity, creating conditions conducive to thunderstorm development. The jet stream, typically flowing from the west or southwest, has begun to meander, trapping low pressure systems and enabling warm air to be drawn up from the south.
READ MORE: What is the jet stream and how does it affect our weather?
Temperature Trends and Humidity
Temperatures have been on the rise, particularly across central and eastern parts of the UK. Forecasts indicate highs reaching the upper 20s Celsius, with London and East Anglia likely to see the warmest conditions. Nights are also becoming warmer, with temperatures remaining in the mid-teens, marking a shift from the cooler nights experienced earlier in the spring. Humidity levels are expected to increase, contributing to a muggy and close feel across much of the country.
Thunderstorm Development
Two main waves of thunderstorms are anticipated. The first is expected to arrive Wednesday night into Thursday, bringing heavy downpours and the potential for hail and gusty winds. A second wave is forecast for late Friday into Saturday, with further intense rainfall and thunderstorm activity. These storms are likely to be hit-and-miss in nature, with some areas experiencing significant rainfall while others remain dry.
⚠️ Yellow weather warning issued ⚠️
— Met Office (@metoffice) June 11, 2025
Thunderstorms across southern and eastern parts of England
Friday 1500 – Saturday 0600
Latest info 👉 https://t.co/QwDLMfRBfs
Stay #WeatherAware⚠️ pic.twitter.com/yGeWzlKGBy
The Spanish Plume Phenomenon
A key feature of the current weather setup is the Spanish Plume—a meteorological pattern where hot, dry air from the Iberian Peninsula is drawn northwards over the UK. This elevated layer of warm air sits above more humid air at the surface, creating a 'lid' that can suppress convection. When this lid is broken, often by a cold front or upper-level forcing, it can result in explosive thunderstorm development. While the current setup shares many characteristics of a Spanish Plume, the air mass appears to originate from northern Africa, passing over the mountains of Spain and potentially carrying Saharan dust, which may enhance lightning activity.
Forecast Uncertainty and Ensemble Models
Forecasting the exact location and intensity of thunderstorms remains challenging. Ensemble models, which run multiple simulations with slight variations, show a range of possible outcomes. While all suggest the likelihood of heavy rain and thunderstorms, the precise areas affected vary. This highlights the importance of staying updated with the latest forecasts, especially for those with outdoor plans.
READ MORE: Glastonbury Festival Weather: A look back at historic extremes
Festival Weather Outlook
With major events such as Download Festival approaching, weather conditions are of particular interest. Download Festival in Leicestershire is expected to see warm and humid conditions on Friday, with a risk of thunderstorms developing into the evening and continuing into Saturday. Sunday is likely to be drier and fresher. For Glastonbury, which begins later in the month, long-range models suggest a higher probability of drier-than-average conditions, although it remains too early to provide a definitive forecast.
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