The Storm

Xynthia had its genesis on 26th February and its life cycle lasted for eight days. Its genesis was related to an already existing low-pressure system that formed on 25th February east of Bermuda over a subtropical area of the North Atlantic (Figure 1.1.1).

Figure 1.1.1 - Geopotential (black lines in gdam), temperature (red lines in ºC) and wind barbs at 500 hPa. Analysis from the ECMWF model for 25/02/2010 at 12:00 UTC. The black cross in the lower left corner represents the surface low with a MSLP of 1006 hPa that later became Xynthia.

This region was characterized by warm and moist air at low levels and an upper level wave embedded in the westerlies. Xynthia´s path was quite unusual, crossing the Atlantic from subtropical latitudes towards Russia. In its early stage over subtropical latitudes, Xynthia showed organized deep convection that was quite well depicted by satellite imagery. Later Xynthia lost its convection activity, mainly after passing the west coast of Portugal (Figure 1.1.2).

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Figure 1.1.2 - MSG Airmass RGB between 21:00 on 25/02/2010 and 00:00 UTC on 02/03/2010. This animation follows the centre of the storm during the whole trajectory.

Xynthia had an explosive development and a rapid displacement between the 26th and 28th, bringing a strong flow of warm air over all continental Europe until its end on 5 March. At the surface, Xynthia was mainly a complex low until its landfall in the early hours of the 28th on the French Atlantic coast. At the upper levels it was rather difficult to detect its related short-wave trough, which was embedded in a large-amplitude upper trough for most of its life cycle.

The severe storm was mainly a windstorm with reports of damaging winds from the Madeira Islands to northern Europe, with gusts exceeding 150 km/h (81 kt) in some regions. This large spatial coverage over the European territory was another distinctive aspect of Xynthia, as can be seen in Figure 1.1.3. There were also reports of large amounts of precipitation (both rain and snow) but these were not as unusual as the wind observations. In western Europe and mainly in France, Xynthia caused around 60 casualties, which resulted from drownings caused by severe storm surge events. Also, the storm caused significant damage and destruction, with trees being uprooted, roofs untiled and electrical grids being seriously affected, cutting off power in over a million households in France and Portugal. Estimated losses caused by Xynthia were about €1.3 billion according to a report published 2 weeks immediately after the event.

Figure 1.1.3 - Xynthia´s trajectory between 25th February 2010 at 00:00 UTC and 1st March 2010 at 18:00 UTC according to 6 hourly ECMWF model analysis. The date/time is plotted every 24 hours after 25th February at 12:00 UTC. Google Image.