The Hautes-Pyrénées, the Pyrénées-Atlantiques, the Landes, the Gers, the Haute-Garonne and the Ariège are placed on yellow alert for violent winds on Thursday January 8 by Météo France.
Météo France has placed several departments on yellow alert for violent winds for the day of Thursday January 9, 2025. This concerns in particular the departments of the South-West such as Hautes-Pyrénées, Pyrénées-Atlantiques, Landes, Gers, Haute -Garonne and Ariège.
The departments of Pyrénées-Atlantiques and Landes are also placed on yellow wave-submersion alert by Météo France.
The weather this Thursday, January 9
Snowfall continues in Nord-Pas-de-Calais in the morning and a few flakes may fall on the Belgian border later in the afternoon. It is still raining in the northern two-thirds of the country in the morning.
The rainy disturbance gradually shifts towards the east affecting at midday an axis going from the South-West to the Grand Est then from the Center-East to the Alps and Jura at the end of the day. Behind, a few residual showers are still possible while the weather becomes dry again in the North-West. This calm in the North-West is temporary, in fact, a new disturbance approaches Brittany in the first part of the night.
In the second part of the night, the disturbance invades the North-West with a risk of snowfall extending from the interior of Brittany, Pays de la Loire and northern Poitou as well as over the Massif Central.
The wind is still strong as the disturbed front passes from the South-West to the North-East with gusts reaching 60 to 80 km/h, temporarily up to 90 km/h over Languedoc-Roussillon and the Alpine ridges. The wind is strengthening on Corsica, a gale is expected overnight on the cape with gusts to 120-130 km/h, 100-110 on the Balagne and the relief. At daybreak, it is between 0 and 1 degree in Nord-Pas-de-Calais, the north of the Somme and the north of Seine-Maritime. Further south, the air is mild, often 9 to 13 degrees, a little cooler in the South-East up to Occitanie.
But cold air gradually invades the northern half during the day, while the southwest, the Mediterranean rim and the Rhône valley remain in mild air with 9 to 13 degrees.
Department by department update
The Hautes-Pyrénées
The Hautes-Pyrénées department is placed on yellow alert for violent winds this Thursday, January 9 by Météo France from 9 a.m. and at least until 7 p.m.
The Pyrenees-Atlantiques
The department of Pyrénées-Atlantiques is placed on yellow alert for violent winds this Thursday, January 9 by Météo France from 9 a.m. and at least until 5 p.m. It is also placed on yellow wave-submersion alert this Thursday from 10 a.m. to 5 p.m.
The Gers
The Gers department is also placed on yellow alert for violent winds this Thursday, January 9 by Météo France from 9 a.m. and at least until 7 p.m.
Haute-Garonne
The Haute-Garonne department is placed on yellow alert for violent winds this Thursday, January 9 by Météo France from 11 a.m. and at least until 9 p.m.
Ariège
The Ariège department is placed on yellow alert for violent winds this Thursday, January 9 by Météo France from 11 a.m. and at least until 9 p.m.
The Landes
The Landes department is placed on yellow alert for violent winds this Thursday, January 9 by Météo France from 6 a.m. and at least until 3 p.m. It is also placed on yellow wave-submersion alert this Thursday from 9 a.m. to 4 p.m.
What is a strong wind?
A wind is generally considered violent and therefore dangerous when its speed reaches 80 km/h in average wind and 100 km/h in gusts inland. But this threshold varies depending on the region, for example it is higher for the coastal regions or the south-east region.
Wind is a movement of air represented by a direction (that from which the wind comes) and a speed. Speed is commonly expressed in kilometers per hour (km/h), but the International System uses meters per second (m/s) as a unit and sailors and pilots use knots (1 knot = 1.852 km/h).
In meteorology, we typically use measurements carried out at 10 meters height:
- average wind over 10 minutes
- maximum gust, i.e. the highest wind speed, recorded during the previous hour.
In marine weather, meteorological services broadcast strong wind warnings from 50 km/h (force 7 Beaufort) in areas near the coast (up to 35 km offshore). Beyond this coastal strip, strong wind warnings are issued from 62 km/h (force 8 Beaufort, gale warning).
The dangers
The damage varies depending on the nature of the wind generating phenomenon. Thunderstorm gusts cause damage of limited extent, waterspouts and tornadoes over a narrow and long band and storms or cyclones over a wider area.
Damage caused by strong winds:
- damaged roofs and chimneys
- trees uprooted
- vehicles displaced on the roads
- power and telephone outages
Road traffic may also be disrupted, particularly on the secondary network in forest areas.
The wave-submersion phenomenon
Marine submersion can cause severe and rapid flooding of coastlines, ports and river mouths.
They are linked to an extreme rise in sea level due to the combination of several phenomena:
Tide intensity
Sea level mainly due to astronomical phenomena and geographical configuration. The higher the coefficient, the higher the sea level at high tide.
The passing of a storm
Producing a rise in sea level (called surge) according to three main processes:
- strong swell or waves which contribute to increasing the water height;
- the wind which exerts friction on the surface of the water, which generates a modification of currents and sea level (accumulation of water as it approaches the coastline);
- the decrease in atmospheric pressure. The weight of the air then decreases on the sea surface and, mechanically, the sea level rises. A decrease in atmospheric pressure of one hectopascal (hPa) is approximately equivalent to a rise of one centimeter in the water level.
Example: A depression of 980 hPa (i.e. a difference of 35 hPa compared to the average atmospheric pressure of 1015 hPa) generates an elevation of approximately 35 cm.
The breaking of waves results in a movement of water masses propagating on the foreshore (area covered and uncovered by the tide). Piers, dykes and other coastal infrastructure can then be breached, weakened or damaged.
The dangers
Strong waves and marine submersions are destructive phenomena, especially when they occur simultaneously. They can affect the entire mainland coastline, including in the Mediterranean where the tide is of low amplitude.
Submersions mainly affect low-lying areas close to the coast. Floods due to marine submersion can, however, invade the coastline several kilometers inland and reach a water height of several meters. Communication routes, homes, and business areas are likely to be flooded and damaged in a few hours, or even less.
Waves can damage coastal infrastructure (sea walls, jetties, etc.) and transport objects or materials (notably pebbles) which then become projectiles capable of injuring people, damaging property or obstructing traffic along the seaside.
Objects not properly secured may be carried away.
Boats, even moored to the pontoon in ports, can be lifted and taken onto dry land.
Near estuaries, the flow of watercourses can also be slowed down or even stopped, which then generates overflows.
The damage can be aggravated in the event of violent gusts of wind, heavy rain, dike ruptures.
Damage to people and property caused by waves and submersion depends on natural factors but also on the implementation of human activities (land occupation). They can be reduced thanks to protective measures (dykes, jetties, dunes) and prevention (restrictions on developments in exposed areas, information, preparation, etc.).
