BBC monthly outlook
Summary
Often unsettled and cooler than normal.
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Saturday 22 May – Sunday 30 May
Winds calming down but staying cool, unsettled.
After an unseasonable stormy weekend in late May, next week is looking a bit more settled in terms of the wind speeds. High pressure is likely to build to the west of the UK through the week, pushing the Atlantic lows from the weekend into Scandinavia. A cool northerly wind will develop in their wake, and this will keep things feeling below average to continue the trend of a cool May. Scattered showers, sometimes thundery, are likely for northern and eastern areas. It's looking drier and sunnier for the bank holiday weekend, but still feeling cooler than normal.
Monday 31 May – Sunday 6 June
A growing chance of scattered afternoon showers.
High pressure over the bank holiday weekend will gradually begin to slide away to the southwest in early June. However, this might take a good part of the week, so a lot of drier and sunnier weather is expected to start. Low pressure from Scandinavia will eventually find its way to the UK from the east, turning things increasingly more unsettled. First in eastern areas, but eventually for most of the country. The rain will most often take the form of scattered afternoon heavy or thundery showers, rather than stormier weather with bands of rain.
With low pressure east of us and high pressure to the southwest, the large scale weather pattern helps promote northerly or north-westerly winds through the week. This will keep the temperatures below average, bringing in air from Iceland and the North Atlantic. Our best bet to get warmer, more summerlike temperatures will be if we can tap into sub-tropical Atlantic or African air, and to do that we need a south-westerly or southerly wind. The main alternate scenario for early June is that high pressure remains overhead instead of shifting away. This is still a cool pattern, but it would remain dry and settled throughout the week instead of turning showery. There is a chance sub-tropical air may filter into western areas, but this is thought to be unlikely. We have high confidence on the temperatures staying below normal, but medium confidence on showery weather later in the week as there is perhaps a 30% chance that high pressure remains in place.
Monday 7 June – Sunday 20 June
Staying cool with a changeable weather pattern.
Through the middle part of June, we expect a rather changeable pattern to emerge across the Atlantic Ocean and Europe. Changeable in the rainfall patterns around highs and lows, but much more consistent in terms of the temperatures. The general pattern of low pressure to our east and high pressure to our west or southwest is expected to remain. This will continue to promote northerly winds and below average temperatures throughout the month. The changeability comes from the high and low pressure systems jostling for control over the UK. There are no clear signals for either to be dominant for the entire month.
Instead, we expect broad low pressure from Scandinavia to bring unsettled, cool weather that will occasionally be broken up by high pressure building in from the southwest. When low pressure is in control, there will be a greater chance for some unseasonably windy days from Atlantic weather fronts. There will also be plenty of sunshine and shower days as well. When high pressure is overhead, it will be more settled, sunnier, and dry, but still feeling a little cool for June. Timing out when we might see high pressure is difficult, and the computer models are having a very challenging time with this. We have high confidence that temperatures will remain below average despite the shifting pressure systems.
The risk scenario is that high pressure remains firmly in charge throughout the month, keeping it dry and sunny. This also brings with it a growing, lesser risk of warmth later in the month. If high pressure shifts into Germany, we may be able to get southerly winds to tap into the hot African air. We expect a 30% chance of the drier, high pressure pattern, and only a 10% chance of the very warm southerly winds.
Further ahead
Although summer weather still eludes us, we will look more in depth at June and try and pin down our chances for some drier, sunnier conditions.
https://www.bbc.co.uk/weather/outlook