Weather warning: Gale and heavy rain linked to hurricane Gérard
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Situation
France lies in the next few days at the heart of a vast low-pressure system, stretching from Northern Europe to the Mediterranean basin and fed by highly unstable polar air.
Amidst this large pool of low pressure, the low pressure deepens. They are the origin of several strong winds in our country: the first in the evening from Sunday to Monday and the second the following night.
On the night Sunday through Monday, the first depression, named Gérard, crosses the north of the country. Dug at 980 hPa near its center, this deep depression raises storms from the Atlantic coast to the north of the country, with gusts approaching 120 km/h on the sea and 90 to 100 km/h on land. The strongest gusts will be observed as the storm’s strong streak of thunderstorms passes, sometimes bringing hail or even snow Monday morning to the plains. In addition, there are fears of flooding as rainfall will fall within hours on the soil which is already saturated with moisture.
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At the foreshore, due to the low tidal coefficient (44), the risk of immersion appears to be limited at high tide.
At the same time as these strong winds, episodes of heavy and perpetual rain occurred in the southwest. This will continue for several days south of Aquitaine and could cause flooding given the significant accumulation expected to be equivalent to 3 weeks to 1 month of rainfall. The Pyrenees will experience blizzards with blizzard conditions high in the mountains, greatly increasing the risk of avalanches.
Observation
this Sunday
At 11 o’clock, on the active tail after yesterday’s disturbances, and prior to tonight’s arrival of hurricane Gérard by Brittany, the winds are still blowing very hard with the passage of a hurricane on the Channel coast and in Brittany with gusts of nearly 100 km/h by the sea, up to 113 km/h in Belle Iles (56). At the Pierres Noires buoy on Molène Island (29), waves nearly 9 m high were measured this morning at 09.30.
At 8 o’clock, the depression, named Gérard, and was responsible for the following night’s strong winds, deepening in the west of Ireland. Up ahead, the wind was already blowing very hard with gusts reaching 125 km/h on Belle Île (56), 115 km/h on Ploven (29), 113 km/h on Brignogan (29), 105 km/h on Barfleur (50 ) and Cap Gris Nez (62) this morning.
Evolution
Regarding the strong wind in the north
This afternoon, On the eve of the depression, the weather was very unstable near the English Channel with gusts approaching 100 km/h as the heavy rains passed.
Tonight from 10pm to Monday 2am, with the arrival of the depression in Brittany, the Atlantic area is most affected by the strongest winds, with gusts of up to 90 to 100 km/h inland and speeds 10 to 20% higher by the sea.
Monday, between 02.00 and 06.00, These gales rapidly develop inland, extending from the center of the Aquitaine basin north of the center of the Massif to Normandy through the Paris region with gusts approaching 80 to 90 km/h, and locally 100 km/h. At sea, winds can reach up to 120 km/h
Monday, between 6:00 a.m. and 10:00 a.m., these strong winds will rise from Burgundy south of Hauts-de-France, with very strong winds, up to 90 km/h in inland gusts.
Monday, between 10:00 and 15:00, winds will still be very strong north of the Seine with gusts approaching 80 to 90 km/h, up to 110 km/h in the Vosges.
From Monday 3pm., the wind will decrease. The lull will be general, but short-lived, as the new secondary low will this time deepen over the Bay of Biscay on Monday evening. This will cause, during the night Monday through Tuesday and Tuesday morning, another high winds with a threat of storm surges at speeds in excess of 110 km/h over the lands of the Aquitaine basin south of Massif Central and towards Languedoc- Roussillon, with a possible peak of 140 km/h by the sea.
Regarding heavy rains in the southwest
Starting this Sunday, the disturbance brought heavy rains south of the Garonne into the Pyrenees, with a rain/snow margin of around 900 meters during the night.
Monday, a very rainy new disturbance much more active than the previous one will cross the southwest. It will block the Pyrenean chain, bringing with it a significant accumulation of precipitation. The disturbance will also cause a severe storm with a gust of thunderstorms Monday evening south of the Garonne.
From tuesday to thursdaysouthwest France will remain the epicenter of severe weather with extremely volatile weather, winds, heavy rains on the plains and snow in the mountains.
During this period of severe weather, 150 to 200 mm of water could fall south of New Aquitaine, the equivalent of 1 to 2 months of rain, which risks causing significant hydrological reactions, in the form of flooding and flooding.
In the mountains, prolonged snowstorm conditions can bring 50 cm to 1 meter of snow to the western Pyrenees from 1,200 meters and 20 to 50 cm to Pyrénées-Orientales. Above 1800 meters, the layer can be 1 to 2 m deep, with the risk of landslides being very strong.
