Weather alert: Stormy and heavy rain associated with storm Gérard
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Situation
France will find itself in the next few days in the middle of a vast low pressure system, which stretches from Northern Europe to the Mediterranean basin and is fed by very unstable polar air.
In the middle of the wide range of low pressure, the low pressure deepens. They are the origin of several storms in our country: the first one in the night from Sunday to Monday and the second one the following night.
In the evening of Sunday to Monday, the first depression, named Gérard, crosses the north of the country. Excavated at 980 hPa near its center, this deep depression brings storms from the Atlantic coast in the north of the country, with gusts near 120 km / h along the sea and 90 to 100 km / h in the within the country. The strongest gusts will be seen as strong lines of storms move through, sometimes accompanied by rain or snow Monday morning down across the plains. In addition, there are fears of flooding as rain will fall within hours on already saturated soils.
On the seashore, due to low tidal coefficients (44), the risk of drowning seems to be limited to high tide.
Along with this storm, a period of prolonged and heavy rains arrived in the southwest. It will continue for several days in the south of Aquitaine and may cause flooding due to significant accumulation which is expected to be equivalent to 3 weeks to 1 month of rain. The Pyrenees will experience a snowstorm with blizzard conditions in the high mountains, greatly increasing the avalanche risk.
Observation
This Sunday
At 6 p.m., while waiting for the arrival of typhoon Gérard, the wind eased slightly due to a decrease in instability. The strongest gusts no longer reach 100 km/h. But this quiet is temporary.
At 15h, winds continue to blow very strongly along the coasts of the English Channel and the Breton islands, gusting to around 100 km/h as heavy rain passes, sometimes storming north of the Cotentin and the Opal Coast. The depression responsible for tonight’s storm is starting to form in the south of Ireland.
At 12, in the active tail following yesterday’s disturbance, and before the arrival of storm Gérard tonight in Brittany, the wind is blowing very strongly in the passage of storms along the Channel coasts and in Brittany with gusts of almost 100 km/ h next to sea, up to 113 km/h at Belle Ile (56). At Pierres Noires buoy on Molène Island (29), waves almost 9 m high were measured this morning at 9:30 am.
9 o’clock, the depression, named Gérard, and responsible for the storm the next night, deepens to the west of Ireland. Ahead, winds are already very strong with gusts reaching 125 km/h at Belle Île (56), 115 km/h at Ploven (29), 113 km/h at Brignogan (29), 105 km/h at Barfleur ( 50) and Cap Gris Nez (62) this morning.
Evolution
About the storm in the north
Tonight from 10 pm to Monday 2 am, with the arrival of the depression in Brittany, the Atlantic regions were the most affected by the storm, with gusts up to 90 to 100 km/h inland and speeds 10 to 20% higher on the seaward side.
Monday, between 2 am and 6 am, this storm is developing rapidly inland, extending from the center of the Aquitaine basin north of the Massif central to Normandy through the Paris region with gusts close to 80 to 90 km / h, and locally 100 km/h Along the sea, winds can reach 120 km/h
Monday, between 6 am and 10 am, this storm will rise from Burgundy to the south of Hauts-de-France, with very strong winds, up to 90 km / h gusting inland.
Monday, between 10 am and 3 pm, the wind will still blow very strongly north of the Seine with gusts near 80 to 90 km/h, up to 110 km/h in the Vosges.
From Monday 3 pm, the wind will decrease. The calm will be general, but short-lived, as a new secondary low will deepen this time over the Bay of Biscay on Monday night. It will cause, during the night of Monday to Tuesday and Tuesday morning, another strong storm with the threat of stormy gusts to more than 110 km / h in the lands of the Aquitaine basin south of the Massif Central and towards the Languedoc- Roussillon, with possible peaks at 140 km / h by the sea.
About the heavy rain in the southwest
From this Sunday, the disturbance brings good rain south of the Garonne to the Pyrenees, with the rain/snow limit dropping to around 900 meters during the night.
monday, a new very rainy disturbance more active than the previous one will cross the southwest. It will come to block the Pyrenean chain, which will bring a significant accumulation of rain. This disturbance will also bring violent storms with stormy gusts on Monday night south of the Garonne.
Of Tuesday through Thursdaysouth-west France will remain in the middle of the bad weather with very unsettled, windy, heavy rain in the plains and snow in the mountains.
During this period of bad weather, 150 to 200 mm of water can fall in the south of New Aquitaine, which is equivalent to 1 to 2 months of rain, which risks causing a significant hydrological reaction, in the form of floods and floods.
In the mountains, long-term blizzard conditions can bring 50 cm to 1 meter of snow in the western Pyrenees from an altitude of 1,200 meters and 20 to 50 cm in the Pyrénées-Orientales. Above 1800 meters, the layer can reach 1 to 2 m, with the risk of an avalanche that can be very strong.
