On Saturday we saw a number of heavy rain showers group together in what’s known as a ‘squall line’ – a narrow band of thunderstorms, intense rain, hail, and frequent lightning accompanied by brief but very strong gusts of wind and possibly tornadoes.
This squall line swept across Wales and then moved south east across southern parts of England – bringing about 6mm of rain to places in a very short period of time with gusts of wind of around 60mph or more in places.
It also had the characteristics of a cold front, with the temperature ahead of it being around 11°C, falling to 7°C once the squall line had passed.
There have been reports of possible weak tornadoes from some locations, however it’s hard to verify them without pictures or footage because these features are generally too small to be picked up by satellites or weather observation equipment.
It’s also worth noting that squally winds can often be mistaken for tornadoes because these gusts can be sudden and strong – potentially causing very localised damage.
You can see more information on tornadoes and how they form on our website.
What’s the difference between a squall line and a derecho?
They are essentially very similar but a derecho is a larger version – a widespread, long-lived, straight-line wind storm that is associated with a fast-moving band of severe thunderstorms. It’s a popular term in the US where their squall lines are much larger than the ones we get in the UK.