Spain flood map shows areas worst hit since 'apocalyptic' storm hit Valencia, with Barcelona now submerged

Torrential rain has deluged parts of Spain over the past week, causing devastating floods in Valencia which have left more than 200 people dead.

The relentless storms today battered Barcelona and its surrounding areas, with the city's airport submerged in just a few hours this morning.

The intensity of the downpours over recent days has been laid bare in a new map, which is based on data from Spain's national weather service Aemet.

The forecaster predicted that as much as 180mm - or 180 litres of rain per square metre - could fall around Barcelona's El Prat airport in 24 hours today.

The seemingly relentless showers are caused by DANA - a high-altitude isolated depression which builds up huge, water-laden clouds that can stay over the same area for many hours.

When cold air blows over warm Mediterranean waters it causes hotter air to rise quickly and form towering, dense, water-laden clouds that can remain over the same area for many hours, raising their destructive potential.

The event sometimes provokes large hail storms and tornadoes, as seen this week, meteorologists say.

Eastern and Southern Spain are particularly susceptible to the phenomenon due to its position between the Atlantic Ocean and the Mediterranean Sea.

Warm, humid air masses and cold fronts meet in a region where mountains favour the formation of storm clouds and rainfall.

Aemet issued a red alert this morning for the Barcelona coastline, warning of the 'extreme danger' as a result of the 'very intense downpour'.

A deluge of 150mm accumulated at the airport in just four hours this morning, Aemet reported.

It caused the runway and even inside the terminal building to flood, resulting in the cancellation and diversion of dozens of flights.

After days of heavy rainfall on Spain's east and south coast, Aemet now predicts that showers will also hit the north and northwest in the coming days.

Some will be accompanied by storms and are expected to be of 'strong or very strong intensity', the forecaster said, though not on the same scale as last week.

The record-breaking rainfall over the past week came after an almost two-year drought, meaning that when the deluge happened, the ground was so hard that it could not absorb the rain.

The unusually high temperature of the Mediterranean has also increased the risk of flooding.

It had its warmest surface temperature on record in mid-August, at 28.47 degrees Celsius (83.25 degrees Fahrenheit), said Carola Koenig of the Centre for Flood Risk and Resilience at Brunel University of London.

Experts say that drought and flood cycles are increasing with climate change.

As well as Valencia, the worst-hit area, the floods have now affected parts of Catalonia, Castilla-La Mancha, Murcia, Andalusia, and the Balearic islands.

Authorities in Valencia said on Sunday that hopes of finding more survivors are fading days after the most intense rainfall on October 29 triggered catastrophic floods.

Torrents of water wrecked homes and vehicles, leaving locals stranded without power and vital supplies.