Météo France has already placed three Breton departments on orange vigilance for the evening of Wednesday November 1 and is considering red vigilance. The SNCF has already canceled numerous TER journeys.
A large northwest quarter will be swept by storm Ciaran and its violent winds. The gusts should be more powerful on the Breton and Normandy coasts with gusts between 120 and 150 km/h. The French Observatory for tornadoes and violent thunderstorms reports peaks of up to 160 km/h locally. And if it should gradually lose power as it sinks further inland, the wind should remain violent: gusts between 110 and 120 km/h over Normandy and the Pays de la Loire and between 90 and 110 km/h. h approaching Ile-de-France are announced. The storm could even blow as far as the limits of Hauts-de-France and New Aquitaine.
The wind from Storm Ciaran should be accompanied by a “submersion wave phenomenon” with “very strong waves expected” across the entire Atlantic coast. Météo France announces waves between 8 and 10 meters all around the ocean. The Kéraunos observatory fears waves measuring up to 13 meters. It will be necessary to be vigilant to the risk of submersion and flooding which will be reinforced by the fairly low atmospheric pressure which will raise the water level. “Sometimes sustained” precipitation is also mentioned by forecasters.
The risks of wave-submersion are particularly feared in the departments on the Atlantic coast already affected by storm Céline during the last weekend of October. Floods have already occurred in certain coastal towns such as Cap-Ferret, Noirmoutier, Quimper and Pornic and the tides were higher.
Brittany will be affected and could be the region most exposed to Storm Ciaran. Three of its departments are already on orange alert for the night of November 1 to 2, because it is through the Breton tip that the depression will arrive in France before sinking into the lands of the northwest quarter. The Breton coastline and the Normandy coasts should be monitored.
The lands of Normandy and Pays-de-la-Loire could also be affected, as well as the regions of Hauts-de-France, Ile-de-France and Centre-Val de Loire although in these territories the risk seems less significant for the moment according to Météo-France.
To a lesser extent, some departments in the southwest, notably Gironde and Landes, could be swept by the tail of the storm during the night of November 2 to 3 with winds at 100 km/h and waves between 6 and 7 meters. , or even up to 10 meters exceptionally in the Bay of Biscay. Note that the final trajectory of the storm has not yet been finalized and the forecasts could be adjusted.
Storm Ciaran is expected to gain strength as it crosses the Atlantic. This depression coming from the American continent swells under the effect of the very powerful winds of the “jet stream”. The current is a sort of corridor several thousand kilometers long in which depressions circulate freely. It somehow marks the separation between the cold air coming from the north pole and the warm air coming from the tropics, a contrast which only reinforces the depressions.
