| Weather pictures & report of March 11-12 2013 |
| Blowing snow related to an occlusion |
| Synopsis: at 500 hPa a sharpening trough extending from the Atlantic Ocean just west of the United Kingdom via Scandinavia towards northwest Russia was slowly moving southwards. At surface a depression over western France moved eastwards placing the Benelux in a cold E'ly flow of continental air. Related occlusion covered the south of the Benelux, being stationary for over 12 hours with south of it an approaching warm front. Both gave in Belgium an accumulation of 1 cm along the coast, via 10 cm over the center to 15 cm over the southeast. This together in combination with strong winds and subzero temperatures, it lead to severe winter weather, not seen before so late in the season. Pictures taken at Steenokkerzeel and Kampenhout. Hours in local time (CET). |
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Surface analysis of March 12 2013 at 0100 CET. A depression over France
was moving slowly ENE-wards. Related occlusion reached overhead Belgium
and the south Holland, with also a warm front approaching. (Source chart: Belgocontrol)
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Loop of 30 surface analyses of each hour of March 11-12 2013
between 1200-1700 CET with the weather plots showing snow falling over the
southern parts of the Low Countries with always negative temperatures. (Source: meteocentre.com)
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Upper air analysis 500 hPa of March 12 2013 at 0100 CET. A sharpening
trough was extending from the U.K. via Scandinavia to the northwest of
Russia. Its axis passed overhead later that day. (Source chart: DWD via wetter3)
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Upper air analysis 850 hPa of March 12 2013 at 0100 CET. Depression
recognizable over NW-France moved slowly ENE-wards.
Isotherm of -7°C was initially overhead, later it became even colder. (Source chart: DWD via wetter3)
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Upper air analysis Theta W 850 hPa of March 12 2013 at 0100 CET. Very
cold air with negative values was present over the north of Benelux
moving S-wards, sucked in by the depression. (Source chart: Meteocentre.com)
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Observed sounding for Beauvechain of March 11 2013 around 2200 CET.
Negative temperatures at all levels with a frontal inversion in the
lower levels and furthermore well saturated till the tropopauze.
(Source: http://weather.uwyo.edu/upperair/europe.html)
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Loop of forecasted soundings for Brussels of March 12 2013 between
0830-1900 CET. At all levels the temperature remained negative and till
the afternoon well
saturated below 500 hPa. (Source: RASP)
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Forecasted vertical profile and surface temperature for Brussels of
March 11 2013 from
0300 UTC (=0400 CET) and the following 48 hours in steps of 1 hour. Legend of upper map: green-brown-white
is humidity in steps of 10% with darkest green being 90% or more, wind
in kt, temperatures each 5°C. By noon of March 11, the frontal
cloudiness arrived and would clear 24 hours later (In reality the
cloudiness decreased even 5 hours later). Temperature would (indeed)
remain the entire period negative. (Source: Belgocontrol)
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Corresponding precipitation of the same model was not in line with
things that would happen, the model of one run earlier was chosen as in
fact better, this run started on March 10 2100 UTC (= 2200 CET)
and the following 48 hours. Two peak wintry precipitation were visible late
evening of March 11 and the morning of March 12, but in between still
remarkable amounts of snow were predicted (Source: Belgocontrol)
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| 12/03/2013 0100 CET. Satellite picture
(infrared) with frontal cloudiness over France -Germany and Benelux..
Recognizable is also a vortex over mid France.
Source picture: Eumetsat.
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Radar loop (reflectivity in dBZ) from March 11 2013 from 0700 CET onwards. Green colors represents moderate snow, blue colors is light snow. (Source radar picture: Belgocontrol).
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Metars (hours in UTC) of Belgian airport EBBR. Translation: copy paste each obs via
metar-decoder |
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Snow height in cm taken from the synop of 1800 UTC of
March 11 2013. Top: Charleroi with 6 cm, followed by Steenokkerzeel,
Liège & Kleine Brogel. At my location, 5 km from Zaventem, 1 to 2 cm cm
was measured, although it was quite difficult due to the strong winds
which formed small dunes at many places, and at some spots nothing at all.
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Max snow height in cm taken from the synop of 0600-0900-1200-1500 UTC of
March 12 2013. Top: Charleroi with 14 cm, followed by Beauvechain with
13 cm, Florennes 12 cm. At my location, 5 km from Steenokkerzeel 8 cm
was measured, although it was quite difficult to get a clue due to the strong winds
which formed snow dunes at many places up to 30 cm, and in some spots nothing at all.
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11-12/03/2013. Temperature histogram in degrees Celcius in local time (CET)
over 24 hrs taken from an automatic station at Kampenhout. Lowest value
-4,2°C in the forenoon, highest -0,2°C by the evening.
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11-12/03/2013. From the auto station: almost the entire period till the noon of
March 12, light to moderate falls of snow which weren't captured by the
pluviometer. Reason was that the strong winds (see below) blew most of
the time the snow flakes out of the basket.
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11-12/03/2013. From the auto station: rather strong winds up to 21 kt
blowing and drifting the snow.
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13/03/2013. Following night extreme low value for the season with lowest
at Diepenbeek with -14,4°C, followed by Ernage -12,9°C, Kleine Brogel
-12,8°C and then even Steenokkerzeel -12,6°C. These values were the
coldest in Flanders for the entire winter season.
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13/03/2013. Temperature histogram in degrees Celcius in local time (CET)
over 24 hrs taken from an automatic station at Kampenhout. Lowest value
-13,0°C at 0716 CET. In open open air even -14,2°C was recorded. But 5
hours later it became already positive.
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14/03/2013. Two days later, the best glimpse over the Low Countries. A lot of
cumuliform cloudiness over the
area but with some imagination the snow cover can be also be detected
over northern France major parts of Belgium and Germany. (Source: Image courtesy of MODIS Rapid Response Project at
NASA/GSFC)
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12/03/2013. Snow coverage in cm over Europe. (Source: Wetterzentrale)
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13/03/2013. Snow coverage with numbers in cm over Europe. (Source:
Uni-Koeln)
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10-16/03/2013. Taken from an automatic station at Kampenhout, a temperature histogram in degrees Celcius in local time (CET)
over 6 day period from March 10 onwards
A remarkable two days with temperatures staying below 0°C ending Wednesday
morning with an absolutely highlight.
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1-16/03/2013. In contrast, the very mild weather during the first week
of March with on the 5th even +18,2°C.
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15/03/2013. Night of March 14-15 2013 proved also very cold with even
the lowest value in Belgium for the entire winter season: at Elsenborn -17,9°C.
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11/03/2013 1725. Proof of the date when the first snow fell.
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11/03/2013 1714. A view into the garden covered with around 1 cm of
snow.
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12/03/2013 0825. Next morning, after a busy night shift at the airport,
while still snowing around 8 cm could be measured on the table, later in
forenoon added by another cm.
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12/03/2013 0744. Before arriving at home, I left duty and made the usual
route but this time with artic conditions ahead, here passing a
last row of houses at Hummelgem (Steenokkerzeel).
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12/03/2013 0746. Village of Steenokkerzeel in the vicinity in a mist of
blowing snow.
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12/03/2013 0746. Approaching a crossing with no traffic at all.
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12/03/2013 0757. Thing were quite opposite on the main road
Haachtsesteenweg, with jammed traffic heading for Brussels and me
rolling at 30 km/h. A new record of more than 1600 km jammed
traffic was reported that morning over entire Belgium.
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12/03/2013 0802. Almost home after a 20 minute drive... instead of the
usual 5 minutes.
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12/03/2013 0808. Dated 120313, the same car of yesterday but now covered
with almost 20 cm of snow. Most was was blown in from trees and roofs of
houses making a false impression of the real amount that had fallen.
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12/03/2013 0808. Plants beside the car also well covered by snow.
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12/03/2013 0827. A view into the garden.
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12/03/2013 1607. Snow dune formed besides a wall, height approx 30 cm.
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12/03/2013 1608. More snow dunes.
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12/03/2013 1610. More snow dunes.
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12/03/2013 1614. More snow dunes.
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12/03/2013 1650. More snow dunes.
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12/03/2013 1723.
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12/03/2013 1726. Drifting snow.
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12/03/2013 1834. Sunset in the west, so Spring is not far away, but still a snowy landscape.
Maybe this was a once in lifetime experience !
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12/03/2013. My weather webcam was watched on March 12 by over 300
worldwide viewers, 10x the average. Final snow traces disappeared
on March 17.
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