Extratropical Cyclone Dagmar

First Posting | Summary
Posting Date: December 27, 2011, 3:30:00 PM

Windstorm Dagmar has moved across Russia north of St. Petersburg and begun to dissipate, its hurricane-force winds having caused power outages, tree-downings, and landslides and other disruption across northern Scandinavia on Christmas Day and the early hours of today, December 27th. Windstorm Dagmar (also named “Patrick” by the Free University of Berlin, which is a semi-official source for all of Europe and which AIR generally follows) developed very rapidly, the product of a large temperature contrast between cold air moving south from Greenland/Arctic Norway and warm air moving north from the Azores/Iberia. Its formation assisted by a rapid deepening of a low pressure system and an unusually powerful jet stream, Dagmar sped almost due east from the Faroe Islands to Norway’s west coast north of Bergen and proceeded to cut across the country further east toward Sweden and Finland. Some wind gusts reached 233 kilometers per hour (about 145 miles per hour), according to Norway’s Meteorological Institute, which is describing Dagmar as possibly the third worst windstorm to strike the country in the past 50 years. The Swedish Meteorological and Hydrological Institute issued “Class 2” warnings for much of the country, which warn of weather that could pose a danger to the public, cause major damage to property, and cause major disruptions in essential services.

Reported Impacts

Across northern Norway, Sweden, and central Finland people are digging out from Windstorm Dagmar’s snows and damage. Train service in northern Sweden, cancelled on Christmas Day, was expected to begin again this morning, even while several hundred thousand customers remained without power. Utility companies said some failures may last for days. With waves reportedly reaching 20 meters high (65 feet), ferry service along Norway’s west coast was halted and the southbound operation of passenger ships from the northern city of Trondheim was suspended, stranding about 400 passengers in that city. Oil and gas output of Norway’s offshore installations was not affected, Statoil officials reported, although the staffing at two fields was reduced as a precaution. However, because of power outages, two key gas processing plants on shore, the Kollsnes plant north of Bergen and the Nyhamma plant farther north that processes gas from Royal Dutch Shell’s giant Ormen Lange field, were shut on Monday. The Ormen Lange field can supply 20 percent of the U.K.’s gas demand; on Monday flow in the pipeline to Britain dropped to six million standard cubic meters (mcm) per day from 60 million mcm 12 hours earlier. By late afternoon Tuesday, as many as 30,000 households in Norway remained without power and about 250,000 in Norway, Sweden, and Finland all together. With power out Monday, about 250 passengers were stranded on the main rail line between Oslo and Bergen, the country’s two largest cities. Also, several thousand residents in Årdal and Høyanger along the Sognefjord were cut off because of landslides, and in Høyanger and another town, Jølster, people were evacuated. Given the holiday and restricted transportation, damage assessment has only begun. Finance Norway, which coordinates claims from natural disasters in that country, said about 500 damage claims have already been filed, but expected that number to rise “significantly” in the coming weeks. The group said it expected claims will exceed the $46 million paid earlier this year following windstorm Berit. Since Dagmar covered the entire southern, more populated part of Finland, it may have caused even more extensive damage than in Norway, but the Federation of Finnish Financial Services was still compiling loss estimates as of mid-day Tuesday.

Coming Attraction

In the past month several storms have struck northern Europe: Xaver, which came on November 24th and 25th; Yoda, which hit Scotland just one day after Xaver; Friedhelm at the beginning of December; Joachim in mid-December; and then Dagmar (Patrick) on the 26th of this month. At present, another storm is developing and is expected to strike Norway in about two days, on the evening of the 29th, very close to where Windstorm Dagmar has just struck north of Bergen. Such clustering of European wind storms is a well-known and common phenomenon for European extratropical cyclones (or, wind storms), and is explicitly taken into account in the AIR Extratropical Cyclone Model for Europe. The new storm currently has a low minimum central pressure of 975mb—which, however, probably will increase in the next days (meaning the storm itself will weaken). Nonetheless, structures and trees just impacted by Windstorm Dagmar will be subject to more damage when struck again so soon. AIR will continue to monitor both Windstorm Dagmar’s passage and the brewing storm and will provide updates as warranted.

First Posting | Downloads
Posting Date: December 27, 2011, 3:30:00 PM