The Met Office has updated its long-range forecast for the August bank holiday weekend, indicating a chance of another heatwave but with low confidence in local details.
Mixed Picture for the Week Ahead
For the next few days, conditions will vary by region. Tomorrow will be cloudy in the north with outbreaks of rain, turning heavier and more persistent later. Further south, hazy sunshine will develop, making it feel very warm and humid.
From Tuesday to Thursday, the Met Office advised: "Rain gradually clearing to the south throughout Tuesday, introducing fresher conditions. Largely dry in the south Wednesday, otherwise a mix of sunshine and showers. Showers becoming more widespread Thursday."
Rest of August: Changeable but Possibly Warm
The rest of August also has a mixed picture. From Thursday until August 29 - which is the bank holiday Saturday - it is set to be a changeable picture, with many parts of the UK seeing showers or perhaps some longer spells of rain.
This will be followed by high pressure becoming increasingly probable over the north and west, with low pressure to the south of the UK. The Met Office explained: "This will lead to further spells of showers and longer spells of rain, but the north may see more in the way of drier conditions."
Within this broad pattern, there is potential for Atlantic lows to spread across the UK at times, which would bring more widespread rain and perhaps strong winds. Temperatures are more likely to be above normal than below overall, though the possibility of widespread or exceptional heat is perhaps a little lower than in recent weeks.
Bank Holiday Weekend Outlook
The Met Office said the temperatures from the bank holiday Sunday, August 30, to Sunday, September 13 are likely to be "close to the climatological norm".
It added: "This means a broad northwest-southeast split in conditions, with the high becoming centred further to the south than in the latter part of August and with more changeable conditions developing towards the north and northwest. Meanwhile, drier, more settled weather is slightly more likely towards the south and east."
Temperatures are again likely to be near to or above average overall. There is a chance that late season hot spells or heatwaves develop, especially in the south.
When Will We Know More?
The Met Office is known to be extremely accurate over its short-range forecasts. Data shows its 1-day maximum temperature forecasts are almost always right with 96% accuracy. However, working out the true picture of what weather is ahead naturally drops over longer ranges, falling to about 74% for 5-day temperature.
Up to five days, people can get local forecasts which can be generally relied on; however, beyond that, it is impossible to be certain. The Met Office explained: "When looking at forecasts beyond five days into the future, the chaotic nature of the atmosphere starts to come into play - small events currently over the Atlantic can have potentially significant impacts on our weather in the UK in several days' time."
Therefore, whilst we can still forecast the general feel of the weather to a relatively high level of accuracy using our ensemble models, it becomes harder to offer local detail to as high a level of accuracy as our shorter range forecasts. For this reason, our text forecasts for 5 days and beyond are written on the scale of the UK as a whole.
"Our long-range forecast (which is updated on a daily basis) provides an indication of how the weather might change, or be different from normal (i.e. warmer, colder, wetter, drier) across the whole UK. Met Office meteorologists consider output from a range of weather models when writing these forecasts. These models include those from the Met Office as well as models from other global forecasting centres such as the European Centre for Medium-Range Weather Forecasts (ECMWF)."
This means while it is looking hopeful that the bank holiday weekend could be a warm one it will not be until the middle of the week before - around August 24-27 - before the Met Office can give a more accurate picture.
