A meandering jet stream

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  • Synoptic Chart for 1200 Saturday, with the jet stream denoted by the coloured shading. Brighter colours indciate a stronger jet stream. A deep low pressure system can be seen over the Pyrenees, with cold easterly flows over the UK. Credit: MeteoGroup.

    120 hour rainfall totals across southern Europe from 0000 Thursday to 0000 Tuesday. Credit: MeteoGroup.

    120 hour fresh snowfall accumulations from 0000 Thursday to 0000 Tuesday. Credit: MeteoGroup.

  • A meandering jet stream
    25.02.2016 16:44

     

    After a mild weekend, much of the UK saw a drop temperature this week as some of the coldest air of the season flooded southwards. Parts of Scotland have seen snow showers to low levels in recent days and overnight frosts have become widespread,  with temperatures plummeting to below -6C at both ends of the country. The change to colder conditions can be attributed to a shift in the jet stream, which has swung to the south of the UK in recent days. And with the jet stream set to remain well to the south this the weekend, the UK meteorological winter looks set to end on a chilly but relatively dry note, while much more unsettled conditions are in prospect for the Mediterranean.

    Through Friday and into Saturday, the jet stream will strengthen and dive southwards into northern Africa, with a deepening area of low pressure bringing outbreaks of heavy rain and upland snow into Iberia as a result. There will be some significant falls of snow for the Pyrenees, giving a late season boost to the region’s ski resorts, with fresh accumulations of over two feet by the end of the weekend. With snow levels falling to 500m, even Madrid could see some falling snow through Friday night or Saturday. The disturbed weather will shift eastwards across western parts of the Mediterranean, southern France and the Alps through the weekend and the early part of next week. Heavy rain and thunderstorms across northern and central parts of Italy could produce rainfall totals of over 100mm in places, bringing the threat of some flash flooding, while gale force winds and rough seas may lead to some travel disruption. However, southerly winds ahead of the low will bring unusually warm weather to southern Italy, Greece and the Balkans, with temperatures exceeding 20C in places.

    Back in the UK, and the southerly low pressure track will see winds here swing round to the east, maintaining the cold conditions with widespread overnight frosts and a significant wind chill across southern areas. Apart from some patchy rain in the far west on Friday, a build of high pressure to the north over the weekend should keep many areas dry, with just the odd wintry shower around. Things look set to change early next week though as the low pressure track reinvigorates over the North Atlantic. The start of March will therefore be more unsettled as strengthening westerly winds bring showers or longer spells of rain, but with temperatures recovering to near normal values.

    By: Billy Payne