BBC monthly outlook
Summary
A hot spell likely, but low pressure threatens
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Saturday 1 August – Sunday 9 August
An unsettled few days; turning hot again later
After Friday's brief hot weather, a cold front tracking eastwards across the country will introduce less hot air overhead, bringing temperatures closer to the seasonal norm over the weekend. There will be showers too, particularly across central and northern England on Saturday afternoon. Northern Ireland will see showers on Saturday evening and Sunday. Meanwhile, Scotland will only showers on Sunday. On Tuesday, an area of low pressure will approach the north of the UK, with fronts tracking across the country. Northern Ireland, Scotland, northern England and north Wales could see some heavy bursts of rain with gusty winds. The unsettled conditions will move over to southern England by Wednesday, before the frontal system later clears away to the east
Later in the week, from Thursday onwards, there is good a chance for a ridge of high pressure to extend in across the British Isles. A very warm air will plume up from the south bringing plenty of dry, sunny and warm weather through Friday and over the weekend. Temperatures will climb into the 30s Celsius. Later, the ridge of high pressure may end up further east over Europe. This will allow frontal system to encroach in from the Atlantic.This movement could bring a wetter and breezier weekend, particularly in the north and west.
Monday 10 August – Sunday 16 August
Dry and warm; wet spells later in the week
Following on from the previous week, the first half of the week beginning Monday 10th may see dry and warm weather persisting. This will occur if high pressure ridging in from West Europe is able to hold in place, allowing warm air to plume up from the south. However, areas of low pressure may threaten from the northwest, bringing fronts towards northwest Scotland, and perhaps Northern Ireland. In the second half of the week, there is a greater chance of low pressure tracking further south over the UK. This could bring wet and breezy weather more widely, and a return to cooler conditions. Scotland and Northern Ireland will likely remain the wettest and breeziest. Whilst southeast England may hold on to the drier, warmer conditions for a longer time.
The influence of low pressure systems is not certain, though. One cause of uncertainty is the result of potential ex-tropical storms and hurricanes tracking across the Atlantic Ocean. This Atlantic Hurricane season is forecast to be very active, which can have knock-on effects on our weather here in the UK. Tropical storms can ramp-up the jet stream over the North Atlantic and bring low pressure systems towards the British Isles, but their exact track is often uncertain until a few days out.
Monday 17 August – Sunday 30 August
Wettest in the northwest, driest in the south
Through the second half of August, areas of low pressure are expected to track over Iceland and near to the north of the UK at times. With associated fronts extending across the UK, wet and breezy spells of weather look likely. Rainy periods will probably be most frequent across Northern Ireland and Scotland. Whilst England and Wales may only see fleeting spells of wet weather as fronts come and go. In fact, a strong northwest-southeast split in the weather looks probable into late-August. High pressure may ridge in from Europe to give lengthier periods of dry and warm weather over the southeast.Whilst fronts may push into the northwest to give frequent wet spells and fluctuating temperatures.
Because the UK is forecast to sit on the periphery of the two weather types mentioned above, there is considerable uncertainty to the forecast for late-August. One weather type may dominate over the other for an extended period. There is a chance that low pressure areas track further south than expected, which would bring above-average rain to the south instead.
By the same token, high pressure ridging may be more persistent and extensive over the UK, which would bring drier, warmer weather more widely across the country.
Further ahead
High pressure over Europe and low pressure to the north look set to battle it out during August. Next time we'll take another look to see if one weather type looks more favourable than the other.
https://www.bbc.co.uk/weather/outlook