A turbulent week of weather lies ahead
Despite a few heavy showers in places, the weekend just gone has been pretty decent for most of the UK, with spells of sunshine and temperatures in the low to mid 20s Celsius.
However, as with the Olympics, all good things must come to an end, and it seems that this applies to this week’s weather too.
The week ahead looks very unsettled for August, with an unseasonably deep area of low pressure expected on Wednesday, bringing heavy rain and gale-force winds.
So what is the cause of this change to such unseasonable weather? It’s our old friend the jet stream that is going to do two things this week – move to the south of us and speed up.
In previous blogs, I’ve explained that when the jet stream sits to the south of the UK, it puts us in the path of a conveyor belt of low pressure systems. This week, there’ll be three of them arriving on our shores – each bringing wind and rain.
The speeding up of the jet stream has a huge influence on the frequency at which low pressure systems arrive. The faster the jet stream, the more frequently they arrive and the deeper they tend to be – producing heavier rain, more cloud and stronger winds.
One additional factor that will play a notable part this week is the humidity of the air being drawn up into these weather systems. The air will originate from the sub-tropics and contain a lot of energy and a huge source of moisture.
This will make the rain this week particularly heavy, with some thunderstorms mixed in. The latest information suggests that the greatest amounts of rain will fall over the western side of the UK, with 30-50mm likely and 60-80mm over the hills and mountains.
Eastern parts of the UK will also see some rain, but at the moment it looks like it will be a bit hit and miss, with 10-30mm expected.
However, there is some uncertainty with the exact positioning of the heaviest rain, so the distribution of the wettest weather could well change as the week progresses.
Another concern will be the strength of the wind on Wednesday – especially in western areas, where gusts of 50-60mph are possible around the coasts and across the hills.
With trees in full leaf there is a risk of branches or even whole trees being toppled. Also, with it being the summer holidays, there’s a lot of loose equipment such as garden furniture that could easily be blown over.
Looking a little further ahead to next weekend and beyond, there are signs that high pressure will build, with the weather settling down.
There’s a possibility of it turning hot over England and Wales, with temperatures as high as 25-30C. Whilst this may sound tantalising, if it does happen, it’ll be accompanied by fairly high humidity.
Keep an eye here on my blog for further updates, and you can also get the latest five day forecast on the Channel 4 Weather website.