Thunderstorms expected as heatwave ends
All good things must come to an end, and it’s no different when it comes to the British weather. Following our longest hot spell since July 2006, temperatures are going to gradually return to where they should be at this time of year.
For much of July, the jet stream has been to the north of UK, taking low pressure, cloud and rain towards Iceland, leaving us to sit under high pressure and bask in the sunshine.
Provisional figures up to 15 July from the Met Office show that the average maximum daytime temperature has been 21.3C, which is two degrees above normal.
As would be expected given the fine weather, we’ve had well above average sunshine – 77 per cent of the July average, yet it’s only half-way through the month.
The highest temperature of the year so far still stands at 32.2C, recorded at Hampton water works in south west London on 17 July.
There is a good chance that this will be surpassed during Monday afternoon, with the temperature somewhere in south east England reaching 33C, possibly 34C.
Heat to give way to thunderstorms
In the coming days, the jet stream will once again be on the move. It’ll end up sitting to the south of the UK, allowing low pressure to bump our resident area high pressure out of the way.
As this happens, the weather is going to slowly cool down, but also turn much more unsettled with some intense thunderstorms possible.
During this heatwave, high pressure has effectively kept a lid on the atmosphere, with air sinking beneath it, inhibiting cloud formation.
However, as low pressure moves over us, this lid will be removed, allowing the build up of heat and humidity to be released – forming cumulonimbus clouds and thunderstorms.
It’s effectively like taking the lid of a saucepan of cooking popcorn, with the air rising rapidly upwards in the atmosphere.
When and where will the worst thunderstorms be?
The first wave of thunderstorms looks set to arrive in southern parts of the UK in the early hours of Tuesday morning, bringing intense downpours and a risk of flash flooding for the morning commute.
They are then likely to continue northwards across other parts of the UK during Tuesday day time, reaching Scotland during Tuesday night.
As well as torrential downpours and a flash flood risk, there is also likely to be frequent lightning in places.
However, as is always the case with thunderstorms, some places will be hit worse than others and some places may not see any at all.
Don’t forget, you can get the latest forecast – including warnings – on the Channel 4 Weather website. If you capture any interesting weather pictures, please send them to me on Twitter – @liamdutton