Life story

Low pressure DANIEL

(Baptized on the 24^th of December 2015)

On the 23^th of December, a low-pressure area over the Gulf of Maine developed as a result of an outbreak of continental cold air from the North American continent towards the warm Atlantic water. From the center of the low reached a warm front in an eastward direction to the northern Atlantic and a cold front to the northeast of the United States of America. In the following, the low moved very fast eastwards over the Atlantic and was located at 1 am CET about 1500 km east of the Canadian island Newfoundland. The pressure in the center of the low had fallen to about 1006 hPa. The warm front had shifted up to the Azores where it started to rain slightly. The cold front in turn has moved towards the Bermuda Islands.

Because the depression should influence the weather over the European continent in the ensuing days, in the morning of the 24^th of December it was named DANIEL by the meteorologists of the Berliner Wetterkarte.

During the day, the low DANIEL and its frontal system moved rapidly to the northeast, whereat the warm front precipitation entered over the northwest of Spain in the early evening. In the following hours the bands of precipitation spread north over the gulf of Biscay and the northwest french Atlantic coast.

By 1 am CET of the 25^th of December, the center of the low DANIEL was located circa 1000 km southwest of the Irish west coast and pressure has continued to fall below 990 hPa. The warm front reached now from the center up to the northwest of France, where it devolved into the cold front of the preceding low CHUCK with its center west of the Norwegian coast. The cold front ran from the center southwest to the Azores and further southwest over the northern Atlantic. In the warm sector, which is the area of warmer air behind the warm front, streamed warm subtropical air northwards and behind the cold front cold maritime air of polar origin southwards. As a consequence of these different temperate air masses, heavy precipitation developed around the cold front and moved southeast. These heavy rainfalls crossed the Azores in the following hours where they brought very high precipitation sums. For instance, until 7 am CET 35.0 mm precipitation were registered in Lajes on the island Terceira within 24 hours. In Horta on the Ilha do Faial even 54.0 mm were recorded. Additionally, storm gusts of 86.5 km/h in Horta and in Flores on the same named island Ilha das Flores were measured. In the French town Brest 4.0 mm precipitation fell as a result of the warm front of low DANIEL within 12 hours until 7 am and in Lann Bihoue 5.0 mm precipitation was measured. In addition 3.0 mm were registered in the Portuguese city Viana do Castelo-Chafe.

In the following hours, the depression DANIEL chose a more northeastern moving direction straight to Ireland and the United Kingdom. Before noon of the 25^th of December the warm front of low DANIEL passed northern France, southern Germany, the Benelux countries, southern England and Ireland. Especially over the United Kingdom and Ireland occurred heavy rainfalls. On the back side of the warm front warm subtropical air streamed into the South of France and from there on further to the north. In Ciboure at the Gulf of Biscay daily maximum temperatures of 20.9°C have been measured. But also in Melun, south of Paris, the temperature reached unusually mild values of 15.3°C. Furthermore, storm gusts up to 105.6 km/h in Capel Curig in the North of Wales and 101.9 km/h in Lake Vyrnwy were recorded. Moreover, strong winds of 70 to 80 km/h occurred over large parts of the United Kingdom and Ireland.

By midnight of the 26^th of December, the depression DANIEL had drawn to the Irish Sea, where the center was located with an increased pressure of 1006 hPa. The warm front, which movement slowed down, reached from the center to the east over northern England, the North Sea, Denmark and northern Germany to the South of Poland. Along the warm front, a zone of heavy rain moved from England to the North of Germany and the South and East of Denmark, where it lasted several hours. Until 7 am severe amounts of rain fell within 24 hours over northern England, southern Scotland and Ireland. In Capel Curig 137.0 mm were measured, in Bingley 53.6 mm and at the airport of Cork 38.0 mm. But also in Leck in northern Germany 19.2 mm and in the Danish capital Copenhagen 15.3 mm were registered. Apart from that, the amount of precipitation in a stripe from northern France over the Benelux countries and mid Germany locally reached 3 to 8 mm, such as in Le Havre with 7.7 mm, on the Mont-Rigi in Belgium with 7.0 mm or on the German mountain Brocken with 6,4 mm. On the latter, also very strong storm gusts up to 122.5 km/h had been recorded. In the following, the low DANIEL moved very slowly eastwards, which is why the bands of precipitation that occurred on the fronts remained over nearly the same area as the day before. In the afternoon, the low DANIEL moved over the Scottish Highlands and the North Sea, where it strengthened again. It also developed some strong rain showers by the passage of the cold front, in which very strong wind gusts, as in Capel Curig with 137.1 km/h or on the Great Dun Fell, the 847 m high mountain in the middle of England, with 157.5 km/h, occurred again. On the Scottish mountain Cairngorm storm gusts up to 127.9 km/h were registered, too. In the evening, the rain started to change into snow over the Scottish Highlands in the inflowing, cooler air at the backside of the low.

Until the start of the 27^th of December, the low DANIEL has moved over the North Sea between Scotland and Norway and the pressure in its center had fallen to ca. 994 hPa. At this moment, the warm front extended over Denmark to the northeast of Poland and the cold front southwest over southern England to the Atlantic coast. Additionally, the low DANIEL has formed a short occluded front towards the Scottish coast. An occluded front or an occlusion is formed as a combination when the faster moving cold front overtakes the preceding and slower moving warm front. The meeting point of all three fronts is called triple point. The heaviest precipitation in the area of the warm front shifted towards the Skagerrak and brought heavy rainfalls and sleet to the South of Norway and to major parts of Denmark. After it initially snowed over the southwest of Sweden, the snow devolved into sleet and rain with raising temperatures in the morning. In the area around the cold front some rainfalls, strong wind gusts up to 70 km/h and some rain showers occurred.

Until 7 am CET the low DANIEL brought once more high amounts of precipitation from the middle and North of Great Britain to the South of Norway, Denmark and North of Germany. In Capel Curig 77.0 mm were measured again, and in the village of Shap in the North of England 49.8 mm. At the station of Gedser in Southern Denmark 42.0 mm, at the Kap Arkona on the German Baltic sea island Rügen 32.5 mm and in Kristiansand in Southern Norway 44.3 mm have been registered. Furthermore, along the coast of the southwest of Norway occurred storm gusts with 100.9 km/h in Saerheim and 108.1 km/h at the lighthouse of Lindesnes. The core of low DANIEL moved in the proceeding day over the southern peak of Norway towards the South of Sweden, whereat the low weakened and the pressure raised fast. The fronts and the thereby occurring rain, sleet and snow shifted northeast and lessened, too. With the beginning night of the 27^th of December it rained from northern Germany over large parts of Poland and southern Sweden to the South of Lithuania and west of Belarus. North and east of these areas the air remained cold enough so that all precipitation in these regions fell as snow.

At 1 am CET of the 28^th of December the center of low DANIEL was located over the southern part of the Baltic Sea and its pressure had risen up to around 1017 hPa. The depression also occluded more and thus, the occlusion reached from northern Lithuania through the center of the low to the coast of Sweden. The warm front has been located across Eastern Europe to the Black Sea and the cold front from the triple point to the northeast of Germany. The precipitations, especially at the cold front, weakened in the following just as the low DANIEL dragged southeast. In the region around the warm front also formed an air mass boundary, at which the strongest rain- and snowfalls appeared. This phenomenon was very noticeable at the 2 m temperatures at 7 am CET. While in Sluzk in the middle of Belarus only -3.2°C could been measured, the temperature in the 130 km southwest located city Pinsk raised up to +7.4°C, which equals a temperature difference of more than 10°C. Until 7 am CET the precipitation accumulated within 24 hours 14.0 mm in the Swedish city Helsingborg, 12.0 mm in Sluzk and 9.0 mm in the Lithuanian capital Vilnius. In the last two cities most of the precipitation occurred as snow. Hence, a new snow cover of 6 cm in Vilnius and 10 cm in Sluzk has been formed. In the Latvian city Dobele also fell 5 cm of fresh snow. In the course of the 28^th of December the strongest precipitations and the front system moved along the river Dnepr southeast towards the Ukrainian-Russian border. Also the pressure in the center of low DANIEL rose further. In the transient area between the cold and the warm air the precipitation even occurred as freezing rain like in Kiev, where this persisted for several hours in the morning. In the area north of that, it snowed constantly and regionally in a strong intensity. Until the evening the core of low DANIEL and the areas of precipitation moved to the southeast of Ukraine. In Odessa, at the coast of the Black Sea, the maximum temperature raised to spring like temperatures of 14.2°C. By contrast, the temperature in Poltava in the northeast of the Ukraine reached only to -4.6°C.

At 1 am CET of the 29^th of December the center of low DANIEL was located with a pressure of nearly 1019 hPa at the foothills of the Caucasus. Its warm front had moved to the East, the cold front over the Black Sea and Romania to the North of Hungary. In the 24 hour period until 7 am in the southern Russian city Divnoe 15.0 mm and in the Ukrainian city Romny 14.0 mm have been measured which brought 14 cm of new snow. Furthermore, the temperature dropped there in the morning to -12.2°C. In the following hours the low DANIEL moved further eastwards and leaved the area which is analyzed by the Berliner Wetterkarte.

Altogether, the low DANIEL influenced the weather over the European continent for more than 5 days and brought not only heavy rain and storm gusts to the UK and southern Scandinavia, but also regionally high amounts of snow over parts of Eastern Europe.

Geschrieben am 23.03.2016 von Maximilian Steinbach

Berliner Wetterkarte: 27.12.2015

Pate: Daniel Badaroux