Severe thunderstorms threaten disruption on Friday
The past few days have seen quiet weather across much of the UK, thanks to high pressure sitting over us.
However, that will change in the coming days, as low pressure spreads up from the south, bringing a plume of warm, moist air, laden with potential energy.
Heat is a source of energy for the weather – the fuel for the weather’s fire if you like. So this will provide a reservoir of energy in the atmosphere on Friday.
It is this potential energy that is likely to be released, giving a threat of severe thunderstorms to southern parts of the UK.
Where is most at risk?
On Wednesday, the Met Office issued a yellow “be aware” warning to highlight the risk, covering southern England, south Wales, the Midlands and East Anglia.
There are two elements to the expected weather: severe thunderstorms and a more general band of thundery rain.
The severe thunderstorms are expected to be isolated, with most places avoiding them, but the few locations that do experience them could see intense rain, frequent lightning, gusty winds and hail.
The more general band of thundery rain will cover a much wider area, although the impacts from this are unlikely to be as great as those in the areas affected by severe thunderstorms.
Threat of disruption
The few places that see severe thunderstorms will experience intense downpours of rain, which will have the potential to cause some localised surface water flooding, with a lot of rain falling in a short space of time.
In addition, there is likely to be thunder, hail and frequent lightning, which could potentially cause disruption to transport and power supplies, if lightning strikes hit key infrastructure.
The more general band of thundery rain will affect a wider area, with issues likely to stem from occasional lightning strikes and persistent rain, which could give localised flooding, with 25-50mm possible in 24 hours.
Thunderstorms and uncertainty
Predicting thunderstorms carry the same characteristics as predicting showers. Whilst it is easy to identify areas in which they are possible, pinpointing which specific towns or cities will be hit is difficult.
Therefore, there will be constant tweaks to the forecast and warnings, right up until the day they are expected.
Beyond the weekend, it looks like high pressure will build once again, meaning a return to dry, sunny and pleasantly warm weather.