| Weather pictures & report of July 12 2010 |
| MCS (squall line) thunderstorm along convergence line. |
| Synopsis: at 500 hPa, east of a relaxing trough west of the British Isles, our area in a moderate SW'ly flow of warm and humid potentially unstable air. At surface passage of thermal depression, related convergence line enhanced the instability which started already during the night over France. From the morning on, an MCS thunderstorm entered the SW of Belgium weakening on its western side, but by noon reactivating as squall-line over eastern parts with over there isolated wind damage mostly due to downbursts. Over central Belgium it resulted (again within three days) in a nice shelf cloud. All pictures were taken at Kampenhout (central Belgium), hours in local time (CET). |
 |
|
Surface analysis of July 12 2010 at 0800 CET. Related to a thermal
depression over the channel, a convergence line over northwest France
which crossed Belgium during the forenoon from SW to NE. (Source chart: Belgocontrol)
|
|
Loop of 7 surface analyses (of each hour between 0500 - 1200 CET) with
weather plots showing the slow movement of the thermal depression. (Source: meteocentre.com)
|
 |
|
Upper air analysis 500 hPa of July 12 2010 at 1400 CET. Related to a low
between Iceland and Greenland, a long wave relaxing trough over
the British Isles moving eastwards. On the other hand a collapsing high over Austria.
Our area in a strengthening SW'ly airflow. (Source chart: DWD via wetter3)
|
 |
|
Upper air analysis 850 hPa of July 12 2010 at 1400 CET. Recognizable
overhead a moderate SW'ly flow in which the warmest air was already been
evacuated
to the east (dropping from 17 to
13°C). (Source chart: DWD via wetter3)
|
 |
|
Upper air analysis of wetbulb temperatures 850 hPa of July 12 2010 at
1400 CET. In moderate SW'ly flow warmest and humid air over the
eastern parts of Benelux - western Germany with temperatures over there around 17°C. (Source chart:
Meteocentre)
|
 |
|
Loop of forecasted soundings for Brussels of July 12 2010 between
0830-2000 CET. In forenoon unstable from 800 hPa upwards. Furthermore
wind speed shows a moderate low
level (0-3 km) shear of 30 kt and rather strong deep layer (0-6km) shear
of 45 kt. Besides this, SREH 0-3 km
was initially moderate with values >150 m²/s², but when the MCS came in,
this dropped in most places to 100 m²/s² or less). Together with moderate CAPE this enhanced
the risk of
large multicells (MCS) eventually preceded by supercells. (Source: RASP)
|
|
Another loop of forecasted soundings for a 15 hours period (in steps of
three hours) of Brussels from July 12 2010, 0500 CET onwards. Included
are some thunderstorms indices: surface based CAPE went up to little
over 1000 J/kg, KI 33, TT 49, LI -4 = moderate to strong convective
potential which may lead to scattered thunderstorms, isolated severe. (Source: weatheronline.co.uk)
|
|
12/07/2010 0615-1045 CET. Satellite loop in the visual channel.
MCS comes in from the north of France. Severe activity
(mainly downbursts) was only to be found over the (south)eastern provinces
where at the end of this sequence the exploding Cb clouds can be noticed
on a NW-SE orientated line. (Source sat
picture: Eumetsat via Sat24.com)
|
 |
|
Still image of the early morning in the visual channel giving a nice view of the MCS over central
to northern France. (Source pic: Eumetsat)
|
Radar loop (rainfall rate in mm/hr) of July 12 2010 between 0700-1210 CET. An extensive precipitation belt comes in from the SW. Most intense echo's on a squall line (although this line is not clearly visible on these 125 km radius images) were to be found on the eastern side with over there isolated wind damage. Precipitation tops went up to around 11-12 km. (Source radar picture: Belgocontrol)
|
Corresponding discharges of July 12 2010 between 0615-1215 CET. Besides the extreme west all area's were affected, but the intensity was in most places rather modest, but gradually intensifying when over the northeast. (Source lightning picture: Blids)
|
 |
|
12/07/2010. 24 hour overview of the discharges over the Benelux: it was
quite intense in a narrow band just east and west of central Belgium.
(source picture: Buienradar)
|
 |
|
12/07/2010 0938 WSW. Gradually the typical shape of a shelf cloud began
to appear on the western horizon with in the back the control tower of
Brussels Airport.
|
 |
|
12/07/2010 0938 SSW. View of the southern side.
|
 |
|
12/07/2010 0943 WSW. Evolution of northern side.
|
 |
|
12/07/2010 0944 WSW.
|
 |
|
12/07/2010 0945 WNW.
|
 |
|
12/07/2010 0946 WNW.
|
 |
|
12/07/2010 0947 NW.
|
 |
|
12/07/2010 0948 NW.
|
 |
|
12/07/2010 0949 NNW.
|
 |
|
12/07/2010 0943 SSW. Evolution southern side.
|
 |
|
12/07/2010 0946 SSW.
|
 |
|
12/07/2010 0948 S.
|
|
To summarize things: time lapse of the events between 0941-0951 CET with
view to the west showing the approach
and passage of a weakening thunderstorm with shelf cloud and behind
turbulent character of the clouds.
|