Risk of high winds and bad weather this weekend

Weather Channel: You announced a very busy weekend. What to expect?

Scaviner Pascal: Due to high pressure in France this week, disturbances across the north remain at low activity. But the situation will change rapidly, according to Brittany, from Friday night to Saturday. Indeed, atmospheric pressure will drop by 12 hPa in 24 hours on Friday at Finistère, down from 1020 hPa to 1008 hPa, then by 10 hPa on Saturday. This pressure drop is of course not characteristic of a weather bomb, but it is significant enough to cause a rapid and quite significant drop in the weather Saturday over Brittany. The latter is related to the formation of a storm Friday over the North Atlantic, more precisely located at 12TU 1,000 km west of Ireland, and will move quite slowly towards the north of Scotland on Sunday. It could be christened Antoni by the British meteorological service MET OFFICE.

Related to this storm, a very active disturbance, which stretches from the north of the Madeira archipelago to the North Sea, will cross France between Saturday and Monday morning and allow an active trolling situation to settle behind. In the context of this sharp downturn in Western Europe, which will continue until the middle of next week, the weather in France will be extremely volatile. We can expect this weekend, and especially Sunday, possible storms on the Atlantic coast to the Cotentin, gusts of wind in the west, the Pyrenean mountains, Lyonnais and Jura.

Precipitation will also be high due to accumulation at Finistère and Morbihan, with local flooding risks heightened by high soil moisture and strong waves expected on the coast (3 to 5 m with crests of up to 7 m). In the mountains, snow returns to the Pyrenees and Alps, but at still relatively high altitudes with a rain-snow limit of around 1500 m.

What makes current forecasting difficult?

NB: If the general reliability of degradation is high, due to the agreement of most models, on the other hand the precision is limited because certain models differ in terms of intensity. We cannot exclude the formation of a secondary low in a low pressure system that would circulate north of the 40th parallel. If this occurs, this situation will be conducive to the strengthening of local and major winds, but also to the strong convective gusts associated with subtropical wind origins. Doubts about the intensity of this degradation also have an impact on estimates of precipitation rates, the accumulation of which can sometimes be more than double.

Some media talk about the possibility of a hurricane. What’s your analysis?

Strong winds are expected this weekend © Weather Channel

NB: Until recently, this risk was very low, as the low-pressure core circulated far from France, over Scotland, but the aforementioned deepening of the “secondary minimum” could cause a powerful gust. For Sunday, models looking at this possibility in central France and mountainous regions may also record winds reaching the threshold of a hurricane, particularly in the relief of the Massif Central. Therefore, storm risk cannot be completely ruled out, but it is very low (less than 10%) and will affect a limited geographical area.

On January 27, 2021, Hurricane Justine hit the country and on January 9, 2022 saw Hurricane Doreen with sustained winds of 150 km/h in Brittany and 180 km/h in Corsica. Is January the month of storms?

Regis crepe: The month of January statistically is a month for hurricanes, but with great variability from year to year. This month, low-pressure flows struggled to sweep across Europe due to the persistence of an anticyclone over Scandinavia, limiting activity to lows of the Atlantic. Apart from occasional strong winds, the risk of hurricanes appears to be low by the end of the month. The most favorable time for high winds is this weekend and next week, then second two weeks promises to be less choppy, but also cooler.

With this bad weather, can the situation of medium and low altitude resorts, which are currently very complicated due to lack of snow, be improved?

CR: Indeed, the return of disturbances from the Atlantic will be synonymous with the rainy season for most of our country. And with the arrival of cooler air, these rains will turn into snow on our relief from 1400 to 1600 m, by a significant amount. However, these altitudes remain relatively high, and the Vosges, Jura, and Massif Central resorts won’t benefit from them, or only temporarily on Monday, the coolest day in the series. Suffice it to say that the upcoming snowfall will bring a clear increase for stations above 1500 m, while below, this will not change the situation.