The formation of storm Ciaran is confirmed, and it is expected on the French coasts from Wednesday evening. “The strongest winds are forecast for a northwest quarter, notably on the tip of Finistère (Brittany) or even on the tip of Cotentin (Normandy), with gusts of around 120-140 km/h, or even 150 km/h, during the night from Wednesday to Thursday and the morning of Thursday,” specifies François Gourand, forecaster at Météo-France. Inland, it is especially “over Brittany in general” that there will be the strongest winds, “of the order of 100 to 120 km/h. »
For the wave-submersion phenomenon, on the other hand, it is “the entire Atlantic coast which will be concerned, up to New Aquitaine, as well as the Channel coasts. » We expect waves “of 8 to 10 meters on the Atlantic and 6 to 8 meters in the Channel. » The strongest impacts on the coasts are expected “during high seas on Thursday morning at 6 a.m. on the Atlantic, and from 12 p.m. to 2 p.m. on the Channel coasts. » A heavy rainy spell is also feared, “but it will circulate very quickly due to the strong winds. » Winds that could cause trees to fall.
The depression will cross the Atlantic “very quickly” before forming into a storm
The expression “weather bomb” widely used in recent days on social networks, seems appropriate in the context of Ciaran, since it is used “when a depression experiences rapid development, and indeed the Ciaran depression has the seems to meet these criteria, with perhaps up to 30 hectopascals of reinforcement between Wednesday and Thursday morning when it arrives in Western Europe” continues François Gourand. If this “weather bomb” phenomenon is “fairly common in the Atlantic Ocean,” generally “it stays at sea.”
This storm is brewing in “a disrupted meteorological context for several weeks in Western Europe” recalls the forecaster, “with successive depressions”. This depression will form off the coast of the Atlantic, west of Newfoundland, “in the coming hours, and it will gradually strengthen as it crosses the Atlantic Ocean between Tuesday and Wednesday,” explains François Gourand. .
This crossing will be done “very quickly” thanks to “a jet stream [un vent très fort] of altitude which is currently crossing the Atlantic”, and the depression “will take on a stormy character at the end of the day on Wednesday when it will approach Western Europe. »
A priori, “we should emerge from the influence of the storm on Thursday afternoon, even if gales will be expected over the Bay of Biscay and the south-west of the country, during the evening of Thursday and the night of Thursday to Friday. »