Low pressure system PIERRE
(baptized on the 10th of February 2017)
On the 10th of February a low pressure area northwestern of
the Iberian Peninsula was named PIERRE by the meteorologists of the Berliner Wetterkarte, after this atmospheric depression was moving
eastwards over the Atlantic Ocean towards Central Europe. On this date the air
pressure in the center was set at 990 hPa. At an advanced state of development
the depression PIERRE showed an occlusion front
that extended northwards crossing Iceland and eastern parts of Greenland. Occlusion
fronts occur when the faster moving cold front overtakes the corresponding warm
front of a system which is ahead.
Embedded in a trough of low pressure in a height of 5.5 km, that was
reaching to northern Africa, the depression PIERRE had an air pressure
of 1000 hPa on the 11th of February. Its occlusion front was
proceeding to Spitsbergen over the Atlantic
Ocean in a lightweight bow.
On the following day, the active depression PIERRE
moved to the south coast of Portugal with an air
pressure below 995 hPa in its center. From this location the occlusion front
continued moving over Morocco
and finally ended over the Atlantic, roughly on the same latitude as Madrid.
Regions located in the zone of cyclone influence recorded precipitation
quantities of 19 l/m² in Agadir, 32 l/m² in Ourzazate, 16 l/m² in Gibraltar, 21 l/m² in Beja or 17 l/m² in Seville measured in 24 hours until the
evening. Especially the north of Spain
measured maximum gusts of up to 140 km/h in Cerezo de
Arriba or 115 km/h in Nestares, which are storm
forces 12 and 11 on the Beaufort wind scale.
By moving northeastwards, the cyclone with a center air pressure of 995
hPa was located at the northern end of Portugal
on the next day. Around the center of the depression PIERRE
the occluded front of the system extended until it reached the triple point,
where the warm front crossed Spain. To the west of
the warm front the cold front of the system extended from Spain to Morocco.
On the 13th of February, the cyclone PIERRE
mostly influenced Portugal
Uplifting of air masses and clouding led to precipitation around the frontal
system. While most parts of the influenced area only measured low precipitation
rates, some meteorological stations reported 2 l/m² like Lisbon,
5 l/m² like Ponferrada or 7 l/m² like the city Gibraltar.
Situated slightly western from Ireland, the low pressure area PIERRE reached an air
pressure of unchanged 1000 hPa on the 14th of February. Its cold
front continued reaching over the Bay of Biscay, the South of France, parts of
the Mediterranean Sea and finally ended over Algeria.
The warm front of the system advanced over the North Atlantic to the south of Iceland.
Considerable amounts of precipitation were falling in Portugal and in
the south of France. The active
trough was leading to heavy rainfall with amounts of 51 l/m² in La Molina, 46
l/m² in Port Vendres, 34 l/m² in Fisterra
or 59 l/m² in 24 hours at the station on Mont Aigoual,
which is at a height of 1567 m. A temperature drop in higher atmospheric layers
made the precipitation in mountainous regions fall as snow rather than rain.
On the next day the cyclone PIERRE, now
lying western from the British Isles,
was showing a complex frontal system. While one cold front was moving to the
north of Portugal
and connecting to a warm front that was leading to an unnamed cyclone over the
Atlantic, the occluded front dispersed to the north, splitting up into a cold
front that passed Great
Britain and changed into an occlusion that
moved further to France. Also another
warm front was reaching Iceland. After bringing
continuous heavy rainfall to the Iberian Peninsula, the cyclone PIERRE caused
precipitation amounts of only 11 l/m² in Church Lawford
in England, 5 l/m² in Benson or 4 l/m² in the Irish city Gurteen.
On the one hand, the depression PIERRE
was shifting northwards with weakening. On the other hand, the low pressure
trough the cyclone was embedded in was intensified and moved to Central Europe.
As the cyclone PIERRE
further developed, it was forming two low pressure centers. One was situated
northwestern of Scotland
and named PIERRE I and the other cyclone center
PIERRE II was analyzed between Iceland
over the sea. The frontal system of the center PIERRE
I was influencing the British Isles and France, the weather in Scandinavia was determined
by the center PIERRE II. Along the Norwegian coast, precipitation amounts
reached 17 l/m² in Hammerfest, 11 l/m² in Alfjord, 12 l/m² in Bergen
and 7 l/m² in Landvik. Stornoway measured 12 l/m² and
winds of force 8. Aonach Mòr
even reported maximum gusts of 115 km/h and the meteorological station on the Cairngorm Mountains even
122 km/h. The corresponding low pressure trough in 500 hPa above Western and
Central Europe, which was connected to cyclone PIERRE at the western side,
dominated the weather in western Germany with cool and cloudy air that was
analyzed as sub polar sea air. While a day before the sun was shining for nine
hours in most parts of the country, only regions in the east and south that
were influenced by the anticyclone ERIKA reported sunshine durations of more
than four hours on the following day. Cologne had
got two hours of sunshine, Bad Lippspringe one hour
and many towns by the North Sea
not even an hour. Thus, Munich recorded maximum temperatures of 15°C, Berlin
13°C, but Westerland on the island Sylt only 5°C. The weak occlusion with the characteristics
of a cold front advanced east and crossed Germany
over night. Until the next morning, Ingolstadt
reported 5 l/m² in 24 hours, Braunlage 2 l/m² and Hamburg
On the 17th of February, the low pressure system PIERRE still showed two
cyclone centers. The center PIERRE I moved
northeastwards in between Stockholm and Helsinki and the center PIERRE II was located in the north
with an air pressure of below 1000 hPa. The weather front that crossed Germany the day
before was reaching over Finland,
and ended over the Alps.
One cold front of the depression center PIERRE II was moving westwards over the
Norwegian coast, another warm front over Finland, which was connected to a
cold front of a deep forward moving unnamed cyclone situated over Russia.
In the cold maritime air mass maximum temperatures in Germany
did not exceed 10°C. Essen reported 7°C, Dresden 8°C, Rostock-Warnemünde 5°C. The unstable cold air mass was partially
leading to heavy snow fall on higher altitudes with 75 cm of snow in total at
the station Brocken,
although the precipitation was falling as rain later on. Also, Bavaria measured great
quantities of rain like Kempten with 11 l/m² or Munich with 16 l/m². Temperatures
often only reached 3°C like Warsaw, Kalisz or Wielun. Until 7 pm, the weather station in Mlawa reported 6 l/m², Kalisz
5 l/m² and Gdov in Estonia
On the next day, there was only one cyclone center named PIERRE. Situated over
Archangelsk, the air pressure was lower compared to the day before. A weather
front connected the center to another unnamed depression over Norway.
A warm front was moving eastwards crossing Russia and ending at the Black Sea. Another warm
front extended to the east. The weather fronts of the cyclone system continued
with light rainfall and amounts that were mostly less than one liter in 24
hours. Nevertheless, the cyclone PIERRE replaced
cold air mass over Russia with maritime
air masses, so that maximum temperatures rose.
Forming only one center of low pressure, the depression PIERRE
was located over Russia on its last days
of existence on the meteorological map by the Berliner Wetterkarte.
On the 19th of February the cyclone PIERRE deepened to an air pressure of 985
hPa. Its cold front was connected to the warm front of the cyclone QERKIN over Sweden.
Until the following day, the depression PIERRE
was moving northeastwards, so that the 20th of February was the last
day the cyclone PIERRE
Geschrieben am 07.03.2017 von Natja Bublitz
Berliner Wetterkarte: 16.02.2017
Pate: Pierre Carrega