BBC monthly outlook
Summary
Changeable weather through July and into August
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Wednesday 15 July – Sunday 19 July
A north-south split with wet weather for Scotland
For the rest of the working week and into the start of the coming weekend the UK will see a bit of a north-south split in the weather. This is due to a ridge of high pressure that is building in from the southwest, bringing some drier and brighter weather to southern areas. However, a stronger-than-normal low pressure system for July will track near Iceland and bring some outbreaks of rain to northern areas. This will mainly impact Scotland and Northern Ireland.
As the ridge builds in on Wednesday and Thursday, a weak warm front will be pushed through Scotland and bring some bands of rain to northern areas and perhaps into the Midlands as well. Rain will tend to be light and patchy though. By Thursday night and into Friday, a cold front will stall over northern Scotland and just to the north of Northern Ireland, bringing some heavy rain for a time. Southern areas will stay dry and see some decent clear spells and some slightly warmer than normal air.
Into the weekend, high pressure will decline and retreat into the Atlantic, allowing the cold front to drift southeast into England and Wales. However, at this point, the front will tend to be a weak feature. Some patches of light rain are likely, but many areas will stay dry despite the front moving through on Saturday. Southeast England will likely have a mostly dry, warm day on Saturday with the front not arriving until the evening or overnight. Cooler northwest winds will follow behind for northern areas, bringing some scattered showers to the west.
Monday 20 July – Sunday 26 July
Northern areas more frequently wet, windy
As we head into late July, the north-south split for the weather will become much more of a persistent feature in the pattern. In the north, we expect fronts will edge in from the Atlantic at times, bringing intermittent but frequent spells of wet and breezy weather to Scotland and Northern Ireland. With cooler northwest winds following on behind the fronts, temperatures in Scotland will likely trend a little below normal. Any dry spells between fronts will be fleeting.
Meanwhile, high pressure is expected to be to the south of the British Isles and into Central Europe during this week. As a result, southern and central parts of England and Wales should see many dry, settled days with temperatures close to, or slightly above, average. Fronts will move through occasionally, but rain is not expected to be frequent or particularly heavy. The best of the dry and bright weather will be in southeast England, where the week may be mostly dry.
The main risk to the forecast is that the high pressure to the south will tend to be stronger and more overhead throughout the week. This will mean the weather is much drier and calmer, even as far north as Scotland. This will also bring in some warmer than normal weather - but there are not any strong signals for heatwaves.
Monday 27 July – Sunday 9 August
Changeable, with alternating dry and wet spells
For late July and the first few weeks in August, we expect low pressure tracks from the North Atlantic will tend to continue to move into the UK. The main change we expect to see is a gradual reduction in the impacts from nearby high pressure. The result is that lows will move overhead more often, and even southern areas will tend to see more frequently wet and windy weather. There will still be some dry spells, especially in late-July and very early-August, and these will be longer lived in southern areas, but as a whole the country will see more unsettled weather.
However, confidence in the forecast is rather low, more so than normal for this range. Records continue to be broken for early tropical storm formation in the Atlantic this year and a very active hurricane season is forecast. These weather systems tend to have a big impact on European weather and wreak havoc on the long-range computer models, which struggle to see them coming more than a fortnight ahead. We expect that the model skill in forecasting the weather at the three and four week range is likely to be poor at the moment.
The main risk, similar to early weeks, is that high pressure becomes more influential into August, bringing some warmer and drier weather more consistently, along with a risk of heat for southern areas.
Further ahead
Next update: We will hopefully see some better signals for the weather story into early August from the models, but will another Atlantic tropical cyclone throw a spanner in the works?
https://www.bbc.co.uk/weather/outlook