Spain issues red alert as storm threatens 300mm of rain on Alicante and Valencia coasts

Spain's State Meteorological Agency, AEMET, has issued a red weather alert covering the southern coast of Valencia province and the northern coast of Alicante, warning that rainfall could reach 300 litres per square metre over 24 hours, according to [1]. The alert, declared on Saturday 17 October, takes effect at 10am on Sunday, with the most intense rain expected on Sunday 18 and Monday 19 October, according to [1]. Forecasters at AEMET said some areas could see more than 200 litres per square metre within 12 hours, an amount described by the agency as capable of overwhelming drainage systems and causing rapid flooding, according to [1]. One litre per square metre is equivalent to one millimetre of rainfall. The deterioration has been linked to Dana Adam, described by AEMET as the first high-impact isolated upper-level depression to be officially named this season, according to [1]. A DANA is a weather system involving a pocket of cold air trapped in the upper atmosphere which, on meeting warm, moisture-laden air from the Mediterranean, can generate powerful thunderstorms and intense rainfall, according to [1]. AEMET said in a special weather bulletin issued on Friday 16 October that Dana Adam would end several days of unusually warm and settled weather across eastern Spain, according to [1]. The agency added that a high pressure system positioned over the British Isles was forcing moist easterly and north-easterly winds toward Spain's Mediterranean coast, feeding additional moisture into the developing storms, according to [1]. The red alert zone takes in areas of what AEMET has called extreme vulnerability along the coast, including Gandia, Oliva, Pego and Dénia, according to [1]. The agency said the largest rainfall accumulations were expected at Cabo de la Nao on Alicante's north coast, as well as parts of Ibiza and Formentera, according to [1]. Orange warnings, one level below red, have also been issued for southern Alicante and the south interior of Valencia, where more than 60 litres per square metre could fall in an hour and 150 litres per square metre over 12 hours, according to [1]. Eastern Catalonia and Murcia were also forecast to see heavy showers and thunderstorms, though at lower warning levels, according to [1]. AEMET warned the event could trigger localised flooding, particularly in low-lying areas, and sudden rises in rivers, ravines and normally dry watercourses known in Spain as ramblas, according to [1]. The agency said these risks could be heightened in areas where ground already saturated by earlier rainfall had reduced capacity to absorb further water, according to [1]. Strong winds and rough seas were also forecast along the open Mediterranean coastline, according to [1]. Forecasters told Euro Weekly News they remained uncertain exactly where the rain would fall hardest, noting that a small shift in the position of the DANA could change which towns are worst affected, according to [1]. AEMET said conditions were expected to begin improving from Tuesday 20 October, though showers would continue along the coast, according to [1]. AEMET's official warning map is available for residents to check current alert levels by area, according to [1].