Britain is facing the threat of flash flooding as thunderstorms, hail, and strong winds are set to sweep the nation, potentially delivering up to a month's rainfall in just a few hours. The Met Office has issued warnings as drought-stricken areas prepare for unsettled conditions after a prolonged dry spell.
Shifting Weather Patterns
The week began with dry and sunny weather across the UK, with temperatures reaching 25C (77F). However, conditions are expected to turn significantly unsettled from Wednesday. Warm and humid air moving northwards will likely trigger widespread outbreaks of rain, particularly across England and Wales. The south-west of England is anticipated to experience the most significant thundery rain.
Forecasters predict that some areas could receive 20 to 30mm (up to 1.2 inches) of rain within a three to four-hour period. Cumulative rainfall totals of up to 60mm (2.4 inches) are also possible. However, Met Office deputy chief forecaster Mark Sidaway noted that the precise locations for the heaviest rainfall remain uncertain, leading to potential variations in amounts over short distances. A slow-moving band of heavy and potentially thundery rain is forecast to move northwards through England and Wales on Thursday, with a similar risk on Friday.
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Friday could also see an area of low pressure develop, bringing intense downpours. Winds are expected to strengthen, especially in eastern and north-eastern coastal regions.
Impact of Dry Ground
BBC lead weather presenter Sarah Keith-Lucas highlighted the risk of localized flooding due to heavy rain falling on dry and hard ground. This is a significant concern following an exceptionally hot and dry summer that has led to drought conditions across nearly three-quarters of England and all of Wales.
Many areas have experienced extended periods without rain, with some places recording over 50 consecutive dry days. Last month was the driest July on record for England. For instance, East Anglia received only 2mm of rainfall in July, and south-east England has recorded just 3mm so far in August, well below the August average of 53mm for the region.
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The forecasted rainfall for this week could exceed the total precipitation received over the past two months in some drought-affected areas. Seven reservoirs in England are currently classified as having 'exceptionally low' storage levels, an increase from five a week prior.
Broader Climate Concerns
Looking ahead, forecasters have warned that Britain may experience more storms and rain in the autumn and winter. This outlook is influenced by an 'unprecedented' El Niño event. El Niño, characterized by a significant rise in sea temperatures in the tropical eastern Pacific, is known to impact global weather patterns. The Met Office anticipates sea temperatures to rise more than 3C above the long-term average in the coming months, with some climate groups projecting even higher increases. The Met Office has stated that this year's El Niño event is expected to be the largest since the 19th century, with some experts suggesting it could be the strongest in 500 to 1,000 years.