Severe storm XAVER across northern Europe from 5 to 7 December 2013 Dr. Thomas Deutschländer, Karsten Friedrich, Dr. Susanne Haeseler, Christiana Lefebvre; updated: 30 December 2013 Introduction Severe storm XAVER, moving across northern Europe in early December (Fig. 1), caused severe winds with gusts of hurricane force across northern Germany and at higher sites. Schools and some Christmas markets were closed as a precaution. Shipping and rail traffic was shut down in places and flights were cancelled. In the area of the German Bight, several consecutive storm surges occurred due to winds from the northwest. Hallig lowlands were flooded. On the islands, dunes broke off and sand was eroded. After the passing of the cold front of the severe storm, soft hail and snow showers occurred, leading to dangerous street conditions and road accidents. It became wintry for a short time with snow even at lower sites. Fig. 1: Track of XAVER over Europe from 4 to 7 December 2013. [Source: DWD] Other XAVER-affected countries reported similar impacts as Germany. Hemsby in Norfolk on the eastern coast of England was seriously struck, when several cliff-top houses disappeared into the sea as the high tide eroded the cliff below. More than 10 people died Europe-wide due to the storm. 1 Development of XAVER On 4 December 2013, a low formed from a warm front wave over the North Atlantic south of Greenland. It rapidly strengthened to a severe storm during the night to the 5th of December and on the 5th (Fig. 2a and 2b) known under the name of XAVER. On its way across southern Sweden, a squall line in connection with the cold front of the storm reached north-western Germany in the afternoon of 5 December, at which hurricane force gusts occurred (Fig. 2b). Severe storm XAVER reached its peak development on the 5th at 18 UTC with a central pressure of 960 hPa. Then it moved only slowly eastwards. In the maritime Arctic air introduced on the rear side of the cold front rainfall occurred, merg- ing into snow even in the lowland (Fig. 2c, 3 and 4). Severe snow drifts occurred in parts of the highland. Fig. 2a: Surface analysis North Atlantic/Europe on 5 December 2013, 00 UTC. [Source: DWD] 2 Fig. 2b: Surface analysis North Atlantic/Europe on 5 December 2013, 18 UTC. [Source: DWD] Fig. 2c: Surface analysis North Atlantic/Europe on 6 December 2013, 00 UTC. [Source: DWD] 3 Fig. 3: Satellite image of northern Europe with air pressure (in hPa) and wind (direction and speed) on 6 December 2013, 00 UTC. [Source: DWD] Fig. 4: Satellite image of Europe on 6 December 2013, 06 UTC. [Source: DWD] While on 6 December the centre of XAVER moved towards the Baltic, the winds at the Ger- man coasts still blew with storm force. 4 Mean winds and peak gusts in Germany The peak gusts reached between 150 and 160 km/h on 5th/6th December, i.e. hurricane force (Fig. 5). Glücksburg/Meierwik recorded a peak gust of 44 m/s (158.4 km/h) on the 6th. Fig. 5: Peak gusts (in km/h) in northern Germany and surrounding countries. [Source: DWD] Top: on 5 December 2013 between 12 and 18 UTC. Bottom: on 6 December 2013 between 00 and 06 UTC. On the evening of the 5th, 10-minute sustained winds of 103 km/h and more were recorded, especially on the North Frisian coast (Fig. 6). This meant a wind force of Bft 11 (103 to 117 km/h; violent storm), locally even Bft 12 (≥ 118 km/h; hurricane). At that time, the centre of the storm was located over southern Sweden. 5 Fig. 6: 10-minute sustained winds (in km/h) on 5 December 2013, 19 UTC. [Source: DWD] Table 1 shows the maximum wind speeds (peak gusts and 10-minute sustained) on 5 to 7 December 2013. Severe storm XAVER caused high wind speeds in the area of the North Sea not as high as in severe storm CHRISTIAN, which crossed northern Germany at the end of October. 6 5 Dec. 2013 6 Dec. 2013 7 Dec. 2013 max. max. max. peak gust sustained wind peak gust sustained wind peak gust sustained wind station km/h km/h km/h km/h km/h km/h Brocken 153.0 128.9 131.4 96.1 95.4 71.3 List auf Sylt 148.3 103.0 129.2 99.7 90.4 70.2 Spiekeroog (SWN) 148.0 130.3 90.4 Leuchtturm Kiel 145.8 99.4 137.2 108.7 82.4 65.9 Strucklahnungshörn 141.5 130.0 83.9 Fichtelberg 140.4 103.0 145.1 100.8 111.2 81.0 Büsum 136.4 122.8 87.5 Rostock-Warnemünde 135.7 96.5 114.8 90.4 78.8 65.9 UFS Deutsche Bucht 135.7 101.5 83.9 67.7 Hallig Hooge 134.6 118.4 88.6 Fehmarn 131.8 94.0 125.3 94.7 85.0 67.7 Putlos 126.4 110.9 84.6 Helgoland 126.0 90.7 112.0 79.9 85.3 56.9 Bremerhaven 125.3 92.9 109.4 81.0 94.0 64.8 Schönhagen (Ostseebad) 122.4 69.8 108.7 65.5 55.8 37.1 Elpersbüttel 121.7 85.0 120.6 79.2 70.6 50.8 Norderney 121.7 96.1 117.7 90.7 87.5 64.8 Feldberg/Schwarzwald 121.3 99.0 101.5 70.9 53.6 41.4 Boltenhagen 121.0 76.3 100.8 71.6 68.0 50.0 Darßer Ort (SWN) 121.0 120.6 78.8 Arkona 119.5 97.6 124.9 99.4 91.8 64.1 Leck 119.2 77.0 111.2 75.2 70.2 41.8 Greifswalder Oie 118.4 93.2 129.6 98.6 82.8 67.0 Bastorf-Kägsdorf (SWN) 118.1 113.8 83.9 Schleswig 118.1 64.4 97.6 58.7 49.0 27.0 Schwerin 112.7 56.5 86.8 50.4 51.5 32.0 Flensburg (Schäferhaus) 112.3 96.5 45.4 Cuxhaven 111.6 77.0 104.4 74.5 77.0 59.0 Emden 110.9 69.1 105.5 71.6 54.4 35.3 Kahler Asten 110.9 73.4 97.6 64.1 64.4 46.1 Borkum-Süderstraße 109.1 126.4 57.2 Bremervörde 107.6 58.7 84.6 46.1 60.1 34.6 Chieming 107.6 76.0 88.9 59.4 61.6 41.0 Weinbiet 107.6 76.0 80.3 54.7 65.2 48.2 Stötten 106.9 76.0 81.7 61.2 54.7 39.6 Groß Lüsewitz 105.8 65.9 96.1 63.4 68.4 45.0 Barth 103.3 64.8 99.7 68.8 65.5 44.6 Travemünde 103.0 120.2 57.6 Hohenpeißenberg 100.4 53.3 88.9 51.8 58.0 29.5 Ueckermünde 100.1 56.5 88.2 51.5 54.0 34.6 Dresden-Klotzsche 99.4 59.4 83.5 57.6 67.7 45.0 Hamburg-Fuhlsbüttel 99.4 59.8 97.6 59.8 50.0 30.6 Tab. 1: Peak gusts and 10-minute sustained wind speeds. [Source: DWD] 7 Figure 7a shows the development of the highest gusts within 10-minute intervals at the 3 stations List/Sylt, Norderney and Rostock-Warnemünde. Fig. 7a: Development of peak gusts from 10-minute intervals (in km/h) at 3 weather stations from 5 to 8 December 2013. [Source: DWD] Figure 7b shows the development of the 10-minute sustained wind speed at the 3 stations List/Sylt, Norderney and Rostock-Warnemünde. Fig. 7b: Development of 10-minute sustained wind speeds (in km/h) at 3 weather stations from 5 to 8 December 2013. [Source: DWD] 8 In the Baltic Sea, the sustained wind speed remained below gale force till the afternoon of 5 December. With passage of the cold front, the wind in the Baltic Sea increased remarkably and reached the force that prevailed in the North Sea since the early afternoon. Notable are the sustained high wind speeds, persisting during the 6th and weakening only by late after- noon and in the evening of 7 December in the Baltic Sea. The wind speed showed noticeable variations of intensity due to high atmospheric instability. The development of the wind speed at Hamburg-St. Pauli illustrates the high variability of the wind field very well (Fig. 8). Fig. 8: Development of wind speed (in knots) and air pressure (in hPa) at Hamburg-St. Pauli on 5 December 2013. There were some data outages. [Source: DWD] The development of the wind direction in Figure 9 shows the clear turn from southwest to northwest associated with the cold front passage in the afternoon of 5 December. In the Bal- tic Sea, the wind turned at first to the west and then in the course of 6 December to north- west. Different from the North Sea, it kept this wind direction until the end of 7 December. 9 Fig. 9: Development of wind direction (in degree) at 3 weather stations from 5 to 8 December 2013. [Source: DWD] Sea state Severe storm XAVER triggered waves of more than 8 metres, especially in the German Bight and off the Polish eastern coast (Fig. 10a, 10b and 11). Fig. 10a: Wind (arrows), wave height (coloured in metre) and air pressure (lines in hPa) in the area of the North Sea on 6 December 2013, 00 UTC.