The ‘DANA’ weather system behind Spain’s extreme rainfall

The extreme conditions in eastern Spain which saw Valencia get a year’s worth of rain in just eight hours 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.

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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.

But rainfall amounts on Tuesday were extreme, with AEMET, Spain’s meteorological department, reporting 491mm in just eight hours at Chiva, near Valencia.

That’s a staggering amount of rain and more than a year’s worth.

The October average is more like 65mm.

AEMET also reported 230.4mm of rain at Utiel, near Valencia, with 217.2mm of that falling in 12 hours and 141.8mm in just six hours.

Drought conditions and hard, baked ground can increase the risk of flash flooding, but this is probably a minor effect given the amount of rainfall observed.

There have also been in excess of 20,000 lightning strikes from storms since Monday afternoon.

The forecast shows further heavy showers and thunderstorms are likely over the next few days, but they are unlikely to be as widespread or as severe compared to what has been seen.

That said, daily totals could reach 80-100mm of rain, which would bring further impacts.

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Amber warnings have been issued for some regions in Spain for Wednesday, with the Andalucia region likely to see the highest rainfall totals.

Thankfully, the weather looks much more settled later into the weekend and early next week.