Through Quentin PERCEROU, editor
Posted on 12/02/20, updated on 2/13/20 at 4:04 p.m.-
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After the Ciara storm, a new low pressure system will be set up this weekend in north-west Europe. The British meteorological services have named this future depression Dennis.
Tuesday, Met Office has appointed a future Dennis depression that will generate a storm over the British Isles on Sunday. The meteorological context promises to be roughly the same as last weekend, that is to say with a very powerful jet stream (between 350 and 380 km / h) as well as a low pressure complex in the North Atlantic Ocean . At the same time, high pressure conditions are maintained on the side of the Azores.
A “girl” depression could break away from this vast depression complex. Under the effect of the powerful jet stream, this depression could reach a lower atmospheric pressure than storm Ciara : between 925 and 915 hPa depending on certain weather models. If the 915 hPa scenario is approached, storm Dennis could break the record for low pressures for this part of the North Atlantic Ocean, excluding the tropical Atlantic Ocean. The old low pressure record was held by storm Braer in January 1993 with 914 hPa.
This very low pressure, if not record, opposite to the high pressures present in the Azores, will form a very tight pressure gradient over 2000 to 3000 km, and especially on the Anglo-Saxon regions. This will allow, as was the case with Ciara, to have very strong winds. Storm Dennis would run due west, directly north of the British Isles, to cross the North Sea and run aground in Norway.
Saturday : strong wind and heavy rain
Like last weekend, the mean wind will be strong and continuous and the gusts will be even higher. The British Isles will see the wind pick up from Friday evening on the west coasts of Ireland. The night promises to be agitated for the whole of Ireland as for Northern Ireland, with generalized gusts ranging between 80 and 100 km / h. They will be locally stronger on the coasts and capes exposed to the west.
These strong winds will then spread across England, Scotland and Wales on Saturday morning. The regions to the west will be the most exposed, in particular that of Gwynedd which has many reliefs and where gusts at 140 km / h are possible.
In parallel with these violent winds, certain regions should receive heavy rains, notably Wales and the western regions of Scotland from Friday to Saturday when an active cold front passes. Floods are likely to occur.
Sunday: the wind gets stronger
The British Isles will not have time to breathe until a second stage of the storm Dennis will set in place Sunday morning as the storm approaches the closest to Scotland. For the time being, the scenarios diverge somewhat. The majority scenario sees the storm closer to the British Isles, which would cause stronger gusts of wind. In this scenario, they would occur in the northwest of Ireland in the morning. The strong and powerful winds will once again reach Wales, the west of England and Scotland in the afternoon. They will be strong until the night, especially in Scotland where the strongest gusts could be around 160 km / h on the western regions.
Other heavy rains will occur that same day but will affect more Scotland and Northern Ireland.
Consequently, we should still expect major disruptions in transport : suspension of maritime traffic, delays and cancellations of flights for airports as well as for rail traffic. It is also possible that power outages may occur and that the roads may be affected.
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