Floods in Spain: Most destructive storm in decades hits cities including Valencia with death toll at 158 - what is DANA weather phenomenon?

The new weather warnings have been issued today (Friday 1 November) as rescue teams continue their desperate search for people missing. The number of people confirmed dead rose from 95 to at least 158 on Thursday (31 October) with more expected to come as emergency services begin their third day of searching.

Spain’s state weather agency, Aemet, has issued the most severe kind of weather alert in the south west of the country as the province of Huelva was hit by torrential rain. Those hit hardest by the flash flooding in eastern Spain are also expecting more rain, as yellow and amber weather warnings remain in place.

The country is in its second day of an official three-day national mourning. Spain’s prime minister Pedro Sanchez urged residents to stay at home as he warned devastation is “not finished” and declared the worst impacted province of Valencia a “disaster zone”.

Spain’s national weather service said it rained more in eight hours in the Valencian town of Chiva than it had in the preceding 20 months. A man wept as he showed a reporter from national broadcaster RTVE the shell of what was once the ground floor of his home in Catarroja, south of Valencia.

The extreme conditions in eastern Spain can be blamed on an event locally known as Depresion Aislada en Niveles Altos (DANA). This weather situation occurs when the jet stream high up in the atmosphere meanders like a river and creates a cut off area of low pressure.

That can become slow moving or almost stationary, with surrounding high pressure blocking it and allowing heavy rain to fall in the same region. Cool air from the north is drawn across the warmer Mediterranean waters, a situation known to bring severe weather to the area in late summer and autumn when the sea surface temperature is high.

That temperature difference can then enhance storm development and rainfall totals. Red weather warnings have been issued to the public which means the potential for extreme or catastrophic damage to properties, and a threat to life, especially to the vulnerable or to people in exposed areas.

The AEMET state weather agency issued its highest level of alert for the province of Castellon, warning of “very strong storms” and urging people to avoid the area. Further north in the Catalonia region, an amber alert was issued for the city of Tarragona, which lies just 50 miles southwest of Barcelona.

Lesser warnings for heavy rainfall were also issued along much of the country’s western border with Spain, running from the south coast to close to Avila in the north. Those warnings, of up to 60mm of rain in 12 hours, cover an area spanning around 150 miles from east to west, including the popular tourist destinations of Seville and Cadiz.