Devastating flash floods hit the Med

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  • A image taken from Midas showing the high level winds moving within the Jet Stream over norther-western Europe this week.

    An image of a lightning strike taken from the Press Association internal webpage.

  • Devastating flash floods hit the Med
    15.10.2016 16:38

    When we think of the Mediterranean, we think of plentiful sunshine and blue skies. However, parts of northern Spain and southern France were running to grab their umbrellas, as both areas received some impressive rainfall totals during Wednesday of this week. The large rainfall totals were brought about by a large area of low pressure that tracked across the north-western Mediterranean, bringing some lively thunderstorms with torrential rain, frequent lightning, hail and squally winds.


    The rain totals brought severe flash flooding to the area, with streams of water running through villages picking up cars, blocking roads and destroying infrastructure. One of the worst affected areas was in Vilassar de Mar in north-east Spain, where a 60-year-old man sadly passed away after his car got swept away with the torrents of water.

    It was in north-east Spain in Cabrils that recorded one of the highest rainfall totals in the region on Wednesday with 220mm of rain falling in four hours, and a total of 85mm in just half an hour. This is significant, as this is the highest rainfall total recorded in four hours at this station since observations began in 1971. Higher totals were recorded over areas of southern France with Meteo-France reporting a total of 300mm at the Saint-Gervais-sur-Mare station by the time the storms had passed. Such high rainfall rates coupled with what has been a relatively dry summer, meant that the ground quickly became saturated and unable to take the quantity of water that was falling, leading to extreme flash flooding.  

    It is not unusual to see such high rainfall events across the north-western Mediterranean during this time of year. It can be a real mixed bag in terms of the weather experienced. In order to find the reasoning behind the exceptional storms that occurred on Wednesday we need to first turn our attention towards the general synoptic pattern across Europe. Throughout October so far there has been an area of high pressure causing a blocking effect over Scandinavia. The high pressure effectively acts as a barrier to low pressure systems over the Atlantic coming into north-western Europe. As a result the jet stream gets sent further to the south across south-western Europe where deep areas of low pressure then form bringing wet and cool conditions to southern Europe.

    Another aspect to look at that worked hand in hand with the low pressure development from the positioning of the jet stream is the sea surface temperatures of the Mediterranean. At this time of year the sea surface temperatures are warmer than land, which act as a source of energy to the low pressure, causing instability in the atmosphere, and adding to the production of thunderstorms. So with the moist flow of area from the Atlantic, coupled with instability, some very potent thunderstorms were produced over the north-western Mediterranean. The good news is that this clear meteorological set up allowed meteorologists to forecast with high confidence days before the event occurred, and weather warnings were issued by both the Spanish and French meteorology agencies. Sadly though, given the intense nature of the storms, it still proved to be a deadly scenario. 

     

    By: Tom Whittaker