Cyclone Ulli^[4] (also named Cyclone Emil by the Norwegian Meteorological Institute^[5]) was an intense European windstorm. Forming on December 31, 2011 off the coast of New Jersey, Ulli began a rapid strengthening phase on January 2 as it sped across the Atlantic.^[6][7] Ulli was the costliest disaster in January 2012 globally.^[8] The damage from the storm in Glasgow was also compared to a storm in 1968.^[9]

Ulli was one of many storms to affect Europe during the winter of 2011–2012. The storm clustering began in late-November when Xaver and Yoda hit the United Kingdom and Norway. In early to mid-December, Friedhelm, Hergen and Joachim hit northern Europe. Another storm, Patrick hit Scandinavia on Christmas Day.^[10] Ulli was followed by Andrea which formed the next day and struck northern Europe on 5 January.^[11]

The system was first noted over the United States Midwest as a surface trough.^[12] The storm moved offshore on December 31, 2011, when it was named Ulli by the Free University of Berlin.^[4] The low deepened slightly to 1,000 mb (30 inHg) by January 1, 2012 while south of Nova Scotia.^[13][14] By January 2, the storm system was located just east of Newfoundland.^[7][15] From 1800 UTC January 2 to 0000 UTC January 3, the barometric pressure of Ulli plummeted from 983 mb (29.0 inHg) to 970 mb (29 inHg). By midnight on January 3, Ulli was situated to the northwest of Scotland.^[16] The storm then made landfall on Scotland during the early morning the same day with a central pressure of 952 mb (28.1 inHg).^[7][17] Hours later, the storm was named Emil by the Norwegian Weather Service.^[5] By January 4, the storm was centered over southern Norway and it slowly moved across to Finland the next day.^[7][18][19] Ulli began to rapidly weaken as it stalled on January 6, and was absorbed by Windstorm Andrea on January 7.^[1] The storm has been proposed as displaying a Sting jet.^[20]

In the late hours of January 1, Met Éireann issued a national severe weather warning for Connacht and Ulster and forecasters predicting winds speeds up to 87 mph with heavy driving rain. On January 2, the Met Office issued an amber weather warning for most of Scotland for heavy snow and strong winds.^[21] Forecasters predicted wind speeds up to 80 mph, and heavy rain, leading to localized flooding.^[22] During the late hours of January 2, the European Storm Forecast Experiment (ESTOFEX) issued a Level Two warning for southeast England, the Netherlands, north Belgium, north Germany and Denmark.

All low pressure areas that affect Europe are named by the Free University of Berlin.^[23] On some occasions, storms that affect Norway are named by the Norwegian Weather Service.^[24] The Free University of Berlin have six lists of names which they use each year. Every odd year they use male names, while every even year they use female names.^[23]

Forecasters began to predict another storm that would make its way across the North Sea in the coming days, which had already named Andrea.^[52][53] Winds were expected to reach 140 km/h (87 mph) on Wednesday night into Thursday in Germany.^[54] German meteorologists said that the new storm looked more toxic than Ulli.^[55] They also said that Andrea was stronger than Ulli, however, the storm was weaker than Kyrill.^[56] The Met Office issued yellow warnings for wind and rain for parts of England and Wales.^[7]

Due to the unstable post-frontal environment, SkyWarn UK issued a severe thunderstorm warning for Scotland, Wales and the east coast of England for January 4 and January 5.^[57] Since dawn on January 4, hundreds of engineers were trying to restore power to over 50,000 homes in the UK.^[58]

• European windstorm
• List of European windstorms
• Cyclone Xaver
• Hurricane Bawbag
• Cyclone Joachim
• Give photos of the aftermath in Scotland
• gives an as live report during that day in the UK