Severe thunderstorms over parts of France and Italy this weekend

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  • This image shows forecast temperature anomalies over Europe at 12:00 UTC on Saturday 28th May. This effectively shows where we can expect temperatures to be warmer than the long term average (pink and red) or cooler than the long term average (blue). Green land areas are where the temperature will be close to the average. While a lot of Spain will be cooler than normal, the extent of unusual warmth elsewhere is quite impressive. (Copyright, MeteoGroup)

    This image shows the forecast rainfall totals (mm) for the 24hours on Sunday 29th May. Widespread heavy showers and thunderstorms are likely over France, N Italy and Central Europe. Some of the most active and severe thunderstorms will be on the southern side of this mass of wet weather. The UK will tend to have drier conditions with just a few showers. (Copyright, MeteoGroup)

    This image shows the upper air flow pattern over Europe on Saturday (white and red solid lines) and also the energy available to developing thunderstorms. The brighter the colours, the more intense any thunderstorms in these areas will be. Low pressure over Biscay will start to move eastwards over France this weekend, bringing colder air at upper levels in the atmosphere (indicated by the dashed blue lines) and this will act to trigger the thunderstorms activity. (Copyright, MeteoGroup).

  • Severe thunderstorms over parts of France and Italy this weekend
    26.05.2016 14:15

    Over the next few days, temperatures across the near continent are set to rise strongly as we see winds from a southerly direction developing over Spain, France and Germany. On Friday and Saturday, temperatures in Paris with reach 24C, Berlin can expect to see 27C by Sunday and inland parts of central and northern Italy should see the mercury topping out in the low 30s Celsius on Friday and Saturday!

    The UK is more likely to be ‘side-swiped’ by these balmy southerly flows, with our winds blowing from an easterly direction instead. While this is bad news in winter (when easterly winds bring bone chilling cold air from Scandinavia and Russia), at this time of year an easterly  can sometimes bring rather warm conditions to central and western parts of the UK, while eastern coastal counties are cooler, due to the effect of the North Sea.  London will see 19 or 20C over the next few days, the warmest we have seen since the first week in May.

    As warm air builds over central and southern France, the Alps, northern Italy and Germany, we have to be concerned with an area of low pressure that is currently spinning away above the Bay of Biscay. Upstream changes to the jet stream over the North Atlantic this Friday will cause this Biscay low pressure area to be ejected quickly eastwards over France and Cent Europe this weekend. As this occurs, stronger winds and cold air at higher altitudes will overspread the warmth and humidity already in place over the aforementioned areas. This is expected to provide a trigger for the development of widespread heavy downpours and thunderstorms on the near continent.

    Conditions seemed primed for the development of several severe thunderstorms, capable of producing very frequent lightning, large hail (perhaps golf ball sized or larger), intense rainfall capable of flash flooding, strong and damaging winds and perhaps even a tornado! These nasty storms are most likely across south-eastern parts of France, the Alps and northern Italy, where warmth and moist air look to combine best with increasingly strong winds through the depth  of the atmosphere (forecasters call this wind shear).

    At this time of year, walking, hiking, road cycling and mountain biking excursions to the Alps and surrounding regions are very popular, so this weekend’s conditions could be quite disruptive or even dangerous for these activities, especially if people are caught out and not aware of the forecast. Temperatures over the Alps will fall very sharply between Saturday and Sunday as the hot air is rapidly shunted away to the east.

    Back closer to home, the Bank Holiday weekend for the UK promises plenty of dry and fine weather over north-western areas, with a glorious period of early summer weather on the way for western Scotland. Further south and east, there is a greater chance of scattered showers, especially on Saturday across south Wales and south-western quarter of England. By Monday, we need to look to the east for a new spell of wet weather moving slowly westwards. If you want to avoid the rain for the longest on Monday, then heading west looks a good call, based on the latest forecast data.

    By: Matthew Dobson