In the past few days, there has been extreme heat with temperatures staying in the 30s C for eight days and drought declared for parts of Britain. Now, thanks to warm, moist air caught up in a messy low pressure there is welcome rain but also torrential downpours, thunderstorms and the threat of flooding.
Yesterday, a convergence zone developed over Cornwall and Devon, with air from the south coast pushing gently north/northeast, air from the Western Channel heading in east/northeast and with some lift over the hills and moors inland there was vigorous convection. The atmospheric conditions allowed thunderstorms to form and the storms were slow moving. This led to high rainfall totals and flash flooding. The main problem at the moment is that the ground is so hard and dry, heavy downpours don’t soak in. The rain just runs off, joining even more water or sits in huge puddles
Monday's thunderstorms over Cornwall and Devon with lightning strikes and heavy rain
Scotland also saw over an inch of rain, welcome rain with water scarcity issues here too. There has been a rain warning for southern and eastern Scotland this morning with concerns about travel disruption. Schools are beginning to return in Scotland and although there will be drier weather midweek, there will be blustery showers from the west and any sunshine is still strong at this time of year.
Northern Ireland will also see brighter skies, showers moving through at times and feel the cool north wind. Overnight temperatures here and for inland Scotland will be well down into single figures.
Meanwhile for England, although the extreme heat has diminished, Monday saw a top temperature of and today central, southern and eastern England could see up to 27C in any sunny spells but there will be infill from these storms. It will still feel rather muggy but be nearer 21C for most with grey skies.
Looking at the two model outputs for this afternoon you can see the differences in areas with heavy showers. Also, the gaps, the drier areas missing the rain and seeing brighter skies. The UKV model tends to do better in these convective situations although there can still be frustrating differences in location. And that is the problem with forecasting showers and thunderstorms. There is a widespread yellow warning but within that some areas will stay dry, others get soaked, see flash flooding, disruption on the roads or railways, and even lose power from lightning strikes. The impacts can be very localised, yet powerful.
UKV has a fair handle on the thunderstorms already showing at 10am on Netweather Radar
Keep an eye on the Netweather Radar, make sure lightning is ON, use the animation to see how the storms are moving. The storms and downpours continue for England and SE Wales overnight as other parts of the UK become dry and cool.
And the Met Office have a yellow warning for “thunderstorms with torrential rain during Wednesday, bringing possible disruption.” Over southern England into East Anglia. This rain, although welcome, will not help the drought situation. An extended period of rain, a lot of rain not just intense downpours, is needed.