Weather pictures & report of July 27 2013

 

Multicell thunderstorms along convergence lines in warm sector.


Synopsis: at 500 hPa, Belgium east of a sharpening trough in a rather strong SSW flow. Overhead, in the warm sector, two thermal trough crossed in a time window of 12 hours. Both gave MCS thunderstorms on a squall line giving widespread shelf clouds. Pictures of the morning taken by Sebastian Verachtert at Brussels Airport,  pictures of the evening taken by myself at Groenendijk (Nieuwpoort), hours in local time (CET). 

 

Surface analysis of July 27 2013 at 0800 CET. Steering feature is a depression centered over west France. Overhead warm sector conditions with some convergence lines passing by.  (Source chart: Belgocontrol)

 

Surface analysis of July 27 2013 at 2000 CET. A new convergence line was approaching Belgium from the southwest 12 hours later.  (Source chart: Belgocontrol)

 

Upper air analysis 500 hPa of July 27 2013 at 1400 CET. Sharpening trough west of the British Isles. Overhead a rather strong SSW flow of warm and potentially unstable air. (Source chart: DWD via wetter3)

 

Upper air analysis 850 hPa of July 27 2013 at 1400 CET. Recognizable a minor trough over west France, Belgium in a moderate (diffluent) SW flow, advecting warm air (16C). (Source chart: DWD via wetter3)

 

Upper air analysis 850 hPa of July 27 2013 at 1400 CET. Here we take a look at Tw at 850 hPa, with a tongue of warm moist air covering west and mid Europe with Tw exceeding 16C. (Source chart: Meteocentre.com)

 

Loop of forecasted soundings for a 21 hours period (in steps of three hours) of Brussels from July 27 2013, 0500 CET onwards. Included are some thunderstorms indices: surface based CAPE went up to over 2400 J/kg, KI 37, TT 54, LI -10 = strong convective potential which may lead to scattered to frequent thunderstorms. The SREH of 150 m/s, in combi with the moderate to strong CAPE, the environment would be favorable for multicell thunderstorms (MCS) with a risk for a supercell. (Source: weatheronline.co.uk)

 

Loop of forecasted soundings for a 21 hours period (in steps of three hours) of Ostend from July 27 2013, 0500 CET onwards. Included are some thunderstorms indices: surface based CAPE went up to 1200 J/kg, KI 36, TT 53, LI -6 = moderate to strong convective potential which may lead to scattered to frequent thunderstorms. The SREH of 150 m/s, in combi with the moderate to strong CAPE, the environment would be favorable for multicell thunderstorms (MCS) with a risk for a supercell. (Source: weatheronline.co.uk)

 

Forecasted vertical profile and surface temperature for Brussels Airport of July 27 from 0500 CET and the following 48 hours. 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 5C. In the morning hours and late evening of July 27 two zones with humidity up to 225 hPa were crossing, both in environments with rather significant shear in direction (and speed). (Source: Belgocontrol)

 

Forecasted precipitation, 2 meter temperature for Brussels Airport of July 27 from 0500 CET and the following 48 hours. Legend: precipitation darkest green = dynamical rain, light green is convective rain. Wind in kt. In the morning a convective signal is forecasted, the zone of late late evening did forecast only a weak dynamical signal which was corrected to convective in the next run of this model (see below). (Source: Belgocontrol)

 

Forecasted precipitation, 2 meter temperature for Brussels Airport of July 27 from 1100 CET and the following 48 hours. Legend: precipitation darkest green = dynamical rain, light green is convective rain. Wind in kt. (Source: Belgocontrol)

 

Forecasted vertical profile and surface temperature for Ostend Airport of July 27 from 0500 CET and the following 48 hours. 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 5C. Same pattern as Brussels can be detected. (Source: Belgocontrol)

 

Forecasted precipitation, 2 meter temperature for Ostend Airport of July 27 from 0500 CET and the following 48 hours. Legend: precipitation darkest green = dynamical rain, light green is convective rain. Wind in kt. Two peaks in convective rain in morning and evening. After the last precipitation zone also a clear wind shift with increasing speeds. (Source: Belgocontrol)

 

Forecasted precipitation, 2 meter temperature for Ostend Airport of July 27 from 1100 CET and the following 48 hours. Legend: precipitation darkest green = dynamical rain, light green is convective rain. Wind in kt. Next run of this model with even a more intense wind shift. (Source: Belgocontrol)

 

Satellite picture of July 27 at 0800 CET in the visible channel. An MCS thunderstorm over north France is approaching the Belgian border. (Source: Metsat via Wokingham weather)

 

Satellite picture of July 27 at 1100 CET in the visible channel. The MCS thunderstorm has arrived over southern Netherlands, but also still affecting eastern parts of Belgium. (Source: Metsat via Wokingham weather)

 

Satellite picture of July 27 at 1700 CET in the visible channel. An new developing MCS thunderstorm over northwest France. (Source: Metsat via Wokingham weather)

 

Satellite picture of July 27 at 2000 CET in the visible channel. The MCS thunderstorm approaches western parts of Belgium, but would also further grow on its eastern side so that entire Belgium would be affected during the evening and night. (Source: Metsat via Wokingham weather)

 

Radar loop (rainfall rate in mm/hr) of July 27-28 2013 between 0800-0200 CET. Two squall-lines in a time window of 12 hours crossing Belgium. (Source radar picture: Belgocontrol)

 

27/07/2013. Amount of discharges (of two thunderstorms in different colors) over the Benelux with weakest activity over the western and eastern parts of Belgium. It would turn out the day with the highest amount of discharges of the entire summer. (Source picture: Buienradar)

 

Metars (hours in UTC) of some airports. Translation: copy paste each obs via metar-decoder

EBBR = Zaventem (Nossegem)-Brussels

EBBR 270520Z VRB01KT 0200 R25L/0325V1900U R25R/0300V0550N R02/0400V1200U FG SCT001 SCT002 19/18 Q1009 BECMG 1500 BR=
EBBR 270550Z VRB02KT 4500 2000NE BR FEW001 19/17 Q1009 BECMG 5000 BR=
EBBR 270620Z 13003KT 6000 NSC 20/18 Q1009 NOSIG=
EBBR 270650Z 13003KT 080V180 CAVOK 22/18 Q1008 TEMPO 22025G45KT 1500 +TSRAGR BKN007 BKN040CB=
EBBR 270720Z 13003KT 100V160 CAVOK 22/18 Q1009 TEMPO 22025G45KT 1500 +TSRAGR BKN007 BKN040CB=
EBBR 270750Z 25016G28KT 200V290 2500 +TSRA SCT019 BKN040CB 19/16 Q1010 TEMPO 22025G45KT 1500 +TSRAGR BKN007 BKN040CB=
EBBR 270820Z 23005KT 200V260 6000 -TSRA SCT015 BKN041CB 18/15 Q1011 TEMPO 22025G45KT 1500 +TSRAGR BKN007 BKN040CB=
EBBR 270850Z 05003KT 8000 -TSRA FEW010 BKN050CB 18/15 Q1009 TEMPO 22025G45KT 1500 +TSRAGR BKN007 BKN040CB=
EBBR 270920Z 07004KT 040V100 9999 -TSRA FEW007 SCT050CB 18/15 Q1009 TEMPO 22025G45KT 1500 +TSRAGR BKN007 BKN040CB=
EBBR 270950Z 08004KT 050V110 9999 FEW007 18/16 Q1008 RETS NOSIG=
EBBR 271020Z 10006KT 060V130 9999 SCT005 19/18 Q1007 NOSIG=


EBBR 271950Z 07004KT CAVOK 22/20 Q1004 TEMPO 23022G35KT 2000 TSRA BKN014CB=
EBBR 272020Z 08006KT 050V110 CAVOK 23/20 Q1003 TEMPO 23022G35KT 2000 TSRA BKN014CB=
EBBR 272050Z 08005KT CAVOK 22/20 Q1003 TEMPO 23022G35KT 2000 TSRA BKN014CB=
EBBR 272120Z 10006KT 070V160 9999 -TSRA SCT020CB 23/20 Q1004 TEMPO 23022G35KT 2000 TSRA BKN014CB=
EBBR 272150Z 26020G33KT 3000 TSRA BKN014CB 18/17 Q1007 RESHRA NOSIG=
EBBR 272220Z VRB02KT 9999 -TSRA SCT030CB SCT046 19/17 Q1006 RESHRA NOSIG=
EBBR 272250Z VRB01KT 9999 -RA NSC 19/18 Q1005 NOSIG=
EBBR 272320Z 19003KT 160V220 CAVOK 19/18 Q1005 NOSIG=
EBBR 272350Z 17006KT 140V200 CAVOK 19/18 Q1005 NOSIG=

 

EBOS = Middelkerke - Ostend

EBOS 270520Z 02004KT 2200 BR FEW020 19/17 Q1009 BECMG 3000 BR=
EBOS 270550Z 05005KT 2500 BR FEW020 20/17 Q1009 BECMG 3000 BR=
EBOS 270620Z 01005KT 340V050 2500 BR FEW020 20/18 Q1009 TEMPO VRB20G40KT +TSRAGR=
EBOS 270650Z 05006KT 2500 BR FEW004 20/18 Q1008 TEMPO VRB20G40KT +TSRAGR=
EBOS 270720Z 03005KT 2500 TS BR FEW004 FEW030CB 20/18 Q1008 TEMPO VRB20G40KT +TSRAGR=
EBOS 270750Z 21019G30KT 1200 R08/1500N R26/0900VP2000D TSRA BR FEW004 BKN038CB 18/16 Q1009 TEMPO VRB20G40KT +TSRAGR=
EBOS 270820Z 28009KT 6000 -SHRA FEW040CB 18/16 Q1008 RETS TEMPO 3000 SHRA=
EBOS 270850Z 32006KT 7000 -TSRA SCT040CB 18/16 Q1007 RESHRA TEMPO 3000 SHRA=
EBOS 270920Z VRB02KT 9999 FEW015 19/16 Q1007 RETS TEMPO 3000 SHRA=
EBOS 270950Z 12007KT 9000 SCT007 19/17 Q1007 TEMPO 3000 SHRA BKN008=


EBOS 271820Z 10007KT 9999 FEW028TCU 23/18 Q1004 TEMPO 3000 SHRA=
EBOS 271850Z 12004KT 9999 FEW028CB 22/18 Q1004 TEMPO 2500 TSRA=
EBOS 271920Z 09005KT 9999 -SHRA FEW028CB SCT048 21/18 Q1004 TEMPO VRB20G35KT 2000 TSRA=
EBOS 271950Z 24018G32KT 1800 +TSRA FEW003 SCT018CB BKN040 17/15 Q1006 BECMG 3000 TSRA=
EBOS 272020Z 10004KT 070V190 9999 -TSRA FEW005 SCT020CB 17/15 Q1004 BECMG NSW=
EBOS 272050Z 09006KT 9999 FEW020CB 17/15 Q1003 RETSRA NOSIG=
EBOS 272120Z 09007KT 9999 FEW030TCU 17/15 Q1003 NOSIG=
EBOS 272150Z 13005KT 9999 FEW030 17/15 Q1003 NOSIG=
EBOS 272220Z 21008KT 150V240 9999 FEW005 SCT008 BKN040 18/16 Q1004 TEMPO BKN008=
EBOS 272250Z 18008KT 9999 FEW008 SCT014 BKN020 19/17 Q1003 BECMG 24012KT TEMPO BKN008=

 

EBFN = Koksijde

EBFN 271825Z VRB03KT 9999 FEW023 SCT090 BKN140 22/20 Q1004 BLU=
EBFN 271855Z VRB03KT 9999 -RA FEW023 SCT080 BKN110 22/20 Q1004 BLU=
EBFN 271928Z 23024G42KT 1200 +TSRA FEW003 SCT020CB BKN050 21/19 Q1007 AMB=
EBFN 271952Z VRB02KT 3700 TSRA FEW003 FEW020CB SCT030 BKN048 17/17 Q1004 GRN=
EBFN 272009Z 10007KT 5000 -TSRA FEW003 FEW020CB BKN040 17/17 Q1004 RETSRA WHT=
EBFN 272025Z VRB02KT 7000 -TSRA FEW010 FEW020CB SCT040 BKN120 17/17 Q1003 WHT=
EBFN 272040Z VRB03KT 8000 -TS FEW010 FEW020CB SCT040 BKN120 17/17 Q1003 BLU=
EBFN 272055Z VRB03KT 9999 -TS FEW010 FEW020CB SCT040 BKN120 17/17 Q1003 BLU=
EBFN 272125Z VRB03KT 9999 -TS FEW010 FEW020CB SCT120 BKN200 17/17 Q1003 BLU=
EBFN 272155Z VRB03KT 9999 VCTS FEW020CB SCT038 BKN044 17/17 Q1003 BLU=
EBFN 272225Z 18011KT 9999 FEW020 SCT040 BKN130 18/17 Q1004 BLU=

 

EBFS = Florennes

EBFS 270655Z AUTO VRB02KT 9999 FEW110/// BKN130/// 21/19 Q1009 BLU=
EBFS 270707Z AUTO 20011G36KT 6000 FEW038/// SCT075/// BKN130/// 21/18 Q1012 WHT=
EBFS 270708Z AUTO 20013G36KT 3600 FEW038/// SCT075/// BKN130/// 20/18 Q1012 YLO=
EBFS 270709Z AUTO 21016G43KT 1300 FEW038/// SCT075/// BKN130/// 18/18 Q1012 AMB=
EBFS 270715Z AUTO 21026G43KT 3100 VV010/// 17/17 Q1012 RED=
EBFS 270725Z AUTO 22014KT 6000 FEW018/// SCT035/// BKN042/// 18/18 Q1011 WHT=
 

 

27/07/2013. Wind gusts (in knots) taken from the synops of 1200 UTC. Winner was Charleroi with 47 kt, followed by Florennes with 43kt.

 

27/07/2013. Wind gusts (in knots) taken from the synops of 0000 UTC. Winner was Beauvechain & St-Hubert with 45 kt, followed by Koksijde & Ernage with 43 kt.

 

27/07/2013. Taken from an automatic weather station at Kampenhout in local time: rain rate with the two thunderstorms passing by within a 14 hour hour period with an almost identical rain rate of almost 160 mm/h.

 

27/07/2013. Taken from an automatic weather station at Kampenhout in local time: gusts in kt indicating two thunderstorms passing by within a 14 hour period, with the strongest gust in the second storm.

 

27/07/2013. Taken from an automatic weather station at Kampenhout in local time: pressure in hPa indicating two thunderstorms (sudden higher pressure) passing by within a 14 hour period. It reveals that the evening storm had two pulses of strong rain & wind.

 

27/07/2013 0935 SSW. The morning MCS with nice shelf cloud was covered at Brussels Airport by colleague meteorologist Sebastian Verachtert in the following 6 photos.

 

27/07/2013 0935 W.

 

27/07/2013 0939 WNW.

 

27/07/2013 0940 W.

 

27/07/2013 0942 SSE. Whales mouth beneath the shelf passing over.

 

27/07/2013 0945 NNW. Opposite side.

 

27/07/2013 2119 SW. The evening MCS was covered by myself at the Belgian coast. In the far distance a weak arcus / shelf cloud could be detected. Buildings left side are located in Oostduinkerke.

 

27/07/2013 2125 W. Approaching.

 

27/07/2013 2126 W. Approaching.

 

27/07/2013 2126 W. Over the North Sea a more pronounced shelf began to appear ahead the developing MCS thunderstorm.

 

27/07/2013 2127 SSW. Other side inland with approaching arcus & shelf.

 

27/07/2013 2127 SSW. 24 seconds later.

 

27/07/2013 2127 SW.

 

27/07/2013 2128 W..

 

27/07/2013 1928 SSW. 20 seconds later.

 

27/07/2013 1928 SSW. 15 seconds later, arcus almost overhead. A couple dozen seconds later it passed over with gusts of around 40 kt, blustery rain with some small hail stones as well.

 

27/07/2013 2227 SE. A couple of hours later, on the backside of the storm, a few discharges could be captured.

 

27/07/2013 2235 SE.

 

27/07/2013 2305 NE. Nieuwpoort bad on right side. Also with some artificial firework in the far back.

 

27/07/2013 2306 NE.

 

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