Weather Warning: Tornadoes and heavy rain are associated with Storm Gerard
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The situation
France is at the center of a huge low pressure system that will stretch from northern Europe to the Mediterranean over the next few days and be fed by very unstable polar air.
In the middle of this broad set of low pressures, the low pressures deepen. They are at the beginning of several storms in our country: the first one from Sunday to Monday night, and the second one the next night.
During the night from Sunday to Monday, the first depression called Gerard passes through the north of the country. This deep depression near the center of 980 hPa is causing storms from the Atlantic coast to the north of the country, with wind speeds of 120 km/h offshore and 90-100 km/h inland. Monday morning will see the strongest winds as strong blizzard storms move into the plains, sometimes accompanied by sleet or even snow. In addition, there is a fear of flooding, as rain will fall within hours on already saturated soils.
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Offshore, due to low tidal coefficients (44), the risk of drowning at high tide appears to be limited.
Simultaneously with this storm, an episode of continuous and heavy rains began in the southwest. This will last for several days in southern Aquitaine and could lead to flooding given significant accumulations of 3 weeks to 1 month of rainfall are expected. The Pyrenees will experience snowstorms with blizzard conditions in the high mountains, greatly increasing the risk of avalanches.
Observation
This is the market
at 11 o’clock, in an active tail after yesterday’s disturbance and ahead of the arrival of Storm Gerard by Brittany this evening, the wind is still very strong with squalls passing through the Channel coast and Brittany at around 100km/h. h offshore, up to 113 km/h at Belle Ile (56). At Pierres Noires buoy (29) on the island of Molène, waves of about 9 m were measured at 9:30 this morning.
At 8 o’clock, the trough named Gérard, which is responsible for the next night’s storm, deepens west of Ireland. The wind ahead is already very strong, 125 km/h at Belle Île (56), 115 km/h at Plouven (29), 105 km/h at Brignogne (29), Barfleur. (50) and Cap Gris Nez (62) this morning.
Evolution
As for the north wind
this afternoon On the eve of the depression, the weather near the English Channel is very unstable, with gusts approaching 100 km/h as heavy showers pass.
From 10pm tonight to 2am Monday, As the depression approaches Brittany, the Atlantic regions are the most affected by the storm, with winds reaching 90-100 km/h and offshore speeds of 10-20% higher.
Monday, 2 a.m. to 6 a.m., this storm is moving rapidly inland, extending from the center of the Aquitaine basin to the north of the Massif central, through the Paris region towards Normandy at 80-90 km/h, locally 100 km/h. The wind speed can reach 120 km/h by the sea
Monday, 6 a.m. to 10 a.m. this storm will develop from Burgundy to the south of Hauts-de-France, with very strong winds, reaching 90 km/h inland winds.
Monday, from 10:00 to 15:00, the wind will still be very strong north of the Seine, with wind speeds of 80-90 km/h and 110 km/h in the Vosges.
Monday from 3:00 p.m, the winds will decrease. The calm will be general but short-lived as a new secondary low will deepen over the Bay of Biscay, this time Monday 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 into Tuesday night and into Tuesday morning. Roussillon, by the sea with possible peaks of 140 km / h.
As for heavy rainfall in the southwest
From this Sunday a disturbance brings good rain from south of the Garonne to the Pyrenees, the rain/snow limit drops to around 900 meters in the evening.
Monday, a new very wet disturbance will move through the southwest, much more active than before. It will block the Pyrenees chain, causing significant rainfall accumulation. This disturbance will also cause a severe storm with gusty winds to the south of the Garonne on Monday night.
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.
