28 Jul 2014

Thunderstorms and flash floods hit SE England

Weather Presenter

Thunderstorms, torrential rain and hail hit parts of south east England on Monday morning, causing flash flooding and travel disruption.

The intense downpours initially affected East Anglia in the early hours, before forming over Sussex, Surrey, Kent and parts of London.

London Fire Brigade rescued two women from a car which got stuck in flood water near South Ruislip station in the north west of the city. On Twitter, it said that 50 houses in the same area were also affected by flood water.

Firefighters in Essex rescued five people from three neighbouring properties which were flooded in Thaxted.

One family remained on the first floor of their home while crews pumped water from the property after it damaged the electrics.

The rail network suffered significant disruption, with South West Trains stopping Woking-bound trains from calling at Esher, Hersham or Walton-on-Thames because of flooding.

A lightning strike on an electricity sub-station caused delays of up to 30 minutes to journeys between Worthing and Hove and Brighton, which were expected to last into the afternoon.

Meanwhile trains were not calling call at Worthing station in the Hove direction due to flooding in a subway.

A Met Office severe weather warning was in place for today across south east England, to highlight the threat of flash flooding that the thunderstorms pose.

What caused the thunderstorms? 

Over the past week, we've had some very warm and humid air over the UK, which has given us our hottest days of the year so far.

However, the persistence of heat and humidity has meant that there's been a progressive build up of energy in the atmosphere.

Overnight, an area of low pressure interacted with this very warm and humid air and caused the atmosphere to destabilise and release the energy that had built up, leading to thunderstorms.

These thunderstorms not only produced very intense rain, but were also slow-moving due to the wind being light. This meant that the same areas saw torrential downpours for prolonged periods of time, resulting in flash flooding.

The most rainfall recorded in an hour was at Great Dunmow in Essex, where 43mm fell. But elsewhere across Sussex and London, 20-40mm of rain fell in the same length of time.

Flooding in pictures