Extratropical Cyclone Joachim

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Posting Date: December 20, 2011, 8:15:00 AM

Late last week, winter storm Joachim developed over the Atlantic and became a severe extratropical cyclone over Western Europe. With a central pressure that reached as low as 963.8 mb and wind gusts exceeding 150 km/h, the storm’s strength was akin to that of a weak hurricane. Joachim’s warm front carried warm and moist air into Europe, causing heavy rain and snow in combination with high winds. The storm caused power outages and travel disruption in France, Germany, and Switzerland. On the evening of the 15th, the storm entered the English Channel and traveled quickly between the UK and France. As with most cyclones in the northern hemisphere, Joachim’s strongest winds were on the south, or right-hand, side of the track, meaning damage in the UK was very limited. France experienced strong winds over much of the country (see the left panel in Figure 1). Twenty-four hour rainfall accumulations exceeded 50 mm in some regions, according to Météo-France. Joachim caused widespread power outages in northern and western France, with some 300,000 households losing electricity. Train travel in central France was disrupted, but the impact on international flights was limited. Coastal flooding was reported in several coastal departments, including Gironde, Charente-Maritime, Vendee, Loire-Atlantique, Morbihan, and Finistère. Strong winds caused a Maltese cargo ship to run aground in Brittany, spilling 220 tons of fuel. The center of the storm moved into Belgium and then Germany on the morning of the 16th, bringing gale-force winds and heavy precipitation to wide swaths of northwestern Europe. Snow and fallen branches disrupted traffic in western Germany, and train service experienced disruptions and delays. In the mountains of Switzerland and Austria, Joachim brought welcome snowfall to Alpine resorts after an unseasonably dry start to the ski season. In northwest Switzerland, a train derailed after colliding with a fallen tree, causing a few light injuries. More than 100 flights were cancelled at the Zurich airport. Recorded wind gusts in Switzerland exceeded 170 km/h in some mountainous regions. The region affected by Joachim is similar to that of winter storm Xynthia in 2010, although Joachim’s wind speeds are generally lower (see Figure 1). Xynthia’s arrival along France’s central Atlantic coast coincided with high tide, causing violent waves that overtopped sea walls and washed away roads and houses. Wind damage from Xynthia was not the primary source of losses to property. Likewise, at Joachim’s recorded wind speeds, wind damage to well-constructed buildings is likely to be nonstructural in nature, typically restricted to roofs and windows, or caused by toppled trees. There have been no reports of substantial damage to property, and AIR does not currently expect significant insured losses from winter storm Joachim.

Figure 1: Maximum recorded wind gusts from Joachim (left) and Xynthia (right) based on METAR observations (Source: AIR).

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Posting Date: December 20, 2011, 8:15:00 AM