Weather Alert: Heavy rain, risk of flood and gale

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By Gilles MATRICON, meteorologist

The full weather forecast live by phone at
3201*

From Saturday, November 9 at 6:00 am to Monday, November 11 at 0:00.
Situation
A vast low-pressure system stretches from Scandinavia to Ireland to Spain, the Maghreb and Italy, encompassing France. In the middle of this vast low-pressure system, secondary minimums plunge from Ireland to Spain and Italy, causing heavy rains in southwestern France and between Corsica and southern Var.

Observation
This Saturday at 10 am an Atlantic disturbance approaches Brittany and causes rains. These rains, weak for now, already reach the Pyrenean departments where it has already fallen locally 20 to 50mm of water in the last 24 hours with 50mm in Urepel and Laruns (64) and 42mm in Dax (40) in addition to heavy rainfall already fallen since the beginning of the week. On the Pyrenees, the rain / snow limit is around 1000 meters with 50cm of fresh snow measured Saturday morning in Cauterêt (65) at 1535 meters altitude and 40cm at Gourette (64) at 1400 meters altitude.
In Corsica, it has already fallen 40mm of rain in Villanova and Ajaccio since Friday morning.
Evolution
Here is the timeline of this episode of bad weather:

This afternoon, continuous rainfall of moderate intensity is strengthening south of the Garonne, and especially on the western departments of the Pyrenees. It snows heavily above 1400 meters.

Tonight and night, it continues to rain a lot south of the Garonne, still on the departments placed in high risk level, with intensities of 5 to 10mm per hour on the Pyrénées-Atlantiques, and between 2 and 5mm on other departments on alert. A quick but sudden gust of wind sweeps the Vendée and Charente-Maritime gusts up to 110 km / h on the coast between 18 and 21 hours Saturday night.

Sunday, the rains continue by taking a stormy character on the south of Aquitaine. It is expected between 20 and 50mm additional water punctually. With the cooling of the air mass at altitude, the rain / snow limit goes down to 800 meters, Above 1200 meters, it is from 10 to 30cm of fresh snow that are expected and up to 50cm above 1800 meters, adding to the layer of snow already on the ground. These precipitations begin to weaken from 17 hours.

At the same time, a episode of heavy rain storms began Friday in Corsica which suffered punctually violent storms with hailstorms. This very bad weather persists until Monday in the extreme south-east, and especially on the east of Corsica because of a very hollow and stationary depression on the gulf of Genoa which overflows on the Var Sunday. We wait between 50 and 100mm of water on the eastern coast of Corsica, 20 to 40mm on the south of the Var very locally. In Corsica, it snows abundantly with 50cm of snow expected above 1800 meters of altitude and a risk of formation of waterspouts off Bastia.

From Monday morning, weather conditions will improve, before the return of a period of very hectic and winter Wednesday by the west and south, which will give rise to a new special release by our services.

Here are the characteristics of this episode of bad weather:

– between 20 and 80mm of rain (equivalent to 2 to 3 weeks of precipitation) expected between Saturday and Sunday, and up to locally 100 to 150mm on the Pyrénées-Atlantiques, which causes an increase in water levels with an increased risk of overflowing, or even flooding near the low points and the mouth of the Adour, especially at the time of the full seas. Reactions of the Gaves of Oloron and Pau can also cause overflows of the Gaves together, even if this risk seems more limited because of the abrupt cooling expected from 1000 meters of altitude, which will slow the flow of the rivers .
– heavy snowfall on the western side of the Pyrenees with 20 to 30 cm around 1200 meters, up to 60 to 80 cm above 2000 meters, with a significant risk of snowdrifts due to a strong wind from north-west blowing up to 100 km / h in the mountains, which makes traffic conditions very delicate from 1200 meters, with great difficulty to predict on the access roads to the ski resorts of the massif.
– On the Provence Côte d'Azur and Corsica, punctually strong thunderstorms, especially on the island of beauty, with a significant risk of hail and tornado formation at sea and abundant snowfall in the mountains.

List of departments concerned

  • 17 – Charente Maritime Wind – Important Risk

  • 2A – Corse-du-Sud Precipitation – Important Risk

    Thunderstorms – Important Risk

  • 2B – Upper Corsica

    Precipitation – Important Risk

    Thunderstorms – Important Risk

  • 40 – Landes

    Precipitation – Important Risk

    Floods – Important Risk

  • 64 – Pyrénées-Atlantiques

    Precipitation – Important Risk

    Floods – Important Risk

  • 65 – Hautes-Pyrénées

    Precipitation – Important Risk

  • 83 – Var

    Precipitation – Important Risk

    Thunderstorms – Important Risk

  • 85 – Vendée

    Wind – Important Risk



Source link
https://actualite.lachainemeteo.com/alerte-meteo/4723-pluies-fortes-risques-d-inondations-et-coup-de-vent

Dmca

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