The period of cold weather that began in early December ended with a generalized mild spell on Monday.
This thaw is accompanied by a major disturbance which ripples over Brittany for more than 48 hours until Tuesday, causing heavy rains. The average quantities expected are between 50 and 100 mm, with maximums between 100 and 130 mm, i.e. an average of 3 weeks to 1 month of rain, which promises to be remarkable.
In a context of heavy seas with southerly waves of 3 to 4 m and strong south-westerly winds up to 90 km/h in gusts, the flow of rainwater could be hampered on the south coasts of Finistère and Morbihan and cause flooding of rivers (Odet, Aulne, Blavet, Laïta) causing overflows or flooding.
At 3 p.m., the calm is confirmed with dry weather before the arrival of a new rainy degradation expected at the end of the afternoon. The rains will persist for most of the night.
At 12, the lull is underway in Brittany. The rains ended up shifting from the center-west to Normandy, while weakening. The southerly wind is still blowing strongly with peaks of between 80 and 90 km/h on the coast.
At 9 o’clock, sustained rains continue from the Gulf of Morbihan to northern Brittany with moderate intensities between 2 and 4 mm/h. The southwest wind is blowing strong with gusts on the coast reaching 70 to 95 km/h. Over the last 24 hours, it has fallen on average 40 to 60 mm, with up to 64.6 mm in Coray (Finistère), 71.9 mm in Ploërdut (Morbihan), 75.2 mm in Kernascléden (Finistère) and 80 .6 mm in Bannalec (Finistère).
Here are the characteristics of these bad weather in Brittany
A lull of a few hours occurs during the day on Monday.
A new salvo is however expected this evening and next night. Again, up to about 2 weeks of precipitation may fall and will add to existing accumulations. Locally, the accumulations will thus exceed, over the entire 48-hour episode, 130 mm of water in the center of Finistère and Morbihan. In a context of strong seas, with southerly waves of 3 to 4 m and strong south-westerly winds at 90 km/h, the flow of rainwater could be hampered on the south coasts of Finistère and Morbihan and cause flooding of rivers (Odet, Aulne, Blavet, Laïta) causing overflows.
Nevertheless, the expected accumulations being lower than those of the last 24 hours, the consequences should be limited and the overflows not widespread, with levels well below the major reference floods. The yellow alert remains however maintained until Tuesday morning 9h.