Weather Warning: Strong Wind, Heavy Rain and Heavy Snow
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The situation
France is at the center of a large low pressure system stretching from northern Europe to the Mediterranean basin. The general flow is northwesterly and circulates very unstable offshore polar air.
Low pressure depressions associated with the highly dynamic Jet Stream (corridor of strong high-altitude winds) deepen and are the cause of episodes of high winds, heavy rain, and heavy snow in the mountains.
The first depression called Gerard is currently passing through the north of the country. Deepening to 976 hPa near its center, this deep trough produces gale-force winds of 100-130 km/h, locally 150-160 km/h, and 90-100 km/h inland, locally 110 km/h along the northwest coast. / h. The strongest storms occur when lines of strong thunderstorms pass through, sometimes accompanied by sleet. Also watch out for strong winds of 100 to 130 km/h at the tip of Corsica.
At the same time as this hurricane, a continuous and heavy rain episode is observed in the southwest as well as in Corsica. This will last for several days and may cause flooding given the large expected accumulations equivalent to 3 weeks to 2 months of rainfall. The terrain of the Pyrenees and Corsica will be subject to snowstorms with blizzard conditions in the high mountains, greatly increasing the risk of avalanches.
Finally, heavy snowfall also affects the south of the Massif Central on Monday, from 700 m above sea level. We expect 25-30 cm thick and sticky snow around 1000 meters. Another 300m of snow is expected between the Massif Central, Jura and Alps on Tuesday.
Observation
This is Monday
At 11 a.m., the stormy depression lost some intensity as Gerard returned from northern France. Still causing strong winds between Normandy, Centre-Val de Loire and southern Ile-de-France. The wind speed is 113 km/h in Fécamp, 106 km/h in Orléans, 97 km/h in Uzuer (41), 95 km/h in Le Havre, 91 km/h in Amilly (45). 90 km/h in Chateaudun (28), La Brosse-Montceaux (77).
At 9 o’clock in the morningThe strongest winds are still observed in Normandy, with 127 km/h at Port-en-Bessin drifting towards Calvados and the Orne (14). In Caen (14), the wind speed reached 119 km/h, which caused some damage to the agglomeration. In Flers (61), the wind speed reached 103 km/h.
In Corsica, wind speeds reached 160 km/h in Cannanno (2B).
In the south-west, the snowfall increases from 1000 meters in the Pyrenees. Finally, in the Massif Central, from Aveyron to Cantal above 700 meters is the heavy and sticky snow.
at 7 a.m. The concern over Hurricane Gerard extends from the Hauts-de-France to the Pyrenees. 159 km/h at Barneville-Carteret (50), 157 km/h at Pointe du Raz (29), 157 km/h at Groix (56) causing persistent rain and strong winds between Brittany and northern Cotentin (56) and 150
Evolution
About the wind
this afternoon the wind will still blow very strongly north of the Seine, 80-100 km/h inland under stormy showers, reaching 120 km/h in the Vosges terrain.
Monday from 4:00 p.m, the winds will decrease. The calm will be general but short-lived as a new secondary low forms over the Bay of Biscay this evening. This will bring another round of strong winds, with the risk of gusts in excess of 110km/h, south of the Massif Central and towards the Languedoc across areas of the Aquitaine Basin from Monday night into Tuesday and into Tuesday morning. Roussillon, by the sea with possible peaks of 140 km / h.
As for the showers in the south-west and Corsica
This is Monday, a very rainy disturbance is passing from the southwest. It is blocked by the Pyrenees chain, causing significant accumulation of precipitation. The disturbance will also bring gusty winds and gusty winds south of Garonne from Monday into Tuesday and into Tuesday morning.
Of Tuesday through ThursdaySouth-west France will remain at the center of the bad weather, with very turbulent, windy, heavy rain in the plains and snow in the mountains.
During this period of bad weather, 150-200 mm of water can fall in the south of New Aquitaine, corresponding to 1-2 months of rain, which can cause significant hydrological reactions in the form of flooding and flash floods.
Persistent blizzard conditions in the mountains could bring 50 cm to 1 meter of snow above 1,200 meters in the western Pyrenees and 20 to 50 cm in the eastern Pyrenees-Orientales. The layer above 1800 meters can reach a height of 1-2 m, the danger of avalanche can be very strong.
In Corsica, heavy rain fell on the island until Tuesday evening. Accumulations can reach 100-200 mm in the center of the island, equivalent to 1-2 months of rainfall, which can cause flooding, especially when the wind blows during a storm.
About snow
On Monday, a lot of snow fell in the south of the Central Massif from an altitude of 700 m above sea level. We expect 30 cm thick and sticky snow around 1000 meters.
