Interactive overlays: 30th July 2005:06UTC
General information: 30th July 2005:06UTC
A frontal system can be seen over central Europe. The occluded part of the system is quite enhanced and is covering parts of Poland, Denmark and the Netherlands. The cold front part is in found over Switzerland and Bavaria. Embedded to this front on the southside of the Alps a single Cb can be seen. Also interesting is the dark appearance of the warm sector ahead of the front over Slovakia and Hungary.
A frontal system can be seen over central Europe. The occluded part of the system is quite enhanced and is covering parts of Poland, Denmark and the Netherlands. The cold front part is in found over Switzerland and Bavaria. Embedded to this front on the southside of the Alps a single Cb can be seen. Also interesting is the dark appearance of the warm sector ahead of the front over Slovakia and Hungary.
WV6.2
The recognition of the frontal system over central Europe proves to be harder with WV6.2 imagery. The occluded part of the system is quite enhanced and appears as bright and white in WV over the Baltic Sea, Denmark and the North Sea. Cyclonically curved over UK, the Gulf of Biscay into France and further to Belgium a dry band can be seen. On the tip of this dark band some increased convectivity is seen over the Netherlands. A deformation zone can be recognised over Spitsbergen and Skandinavia. A bright cell is seen over Switzerland indicating some convective development that should be looked at in future timesteps. More interesting are the convective cells that have emerged over Belarus and Ukraine. They develop on a pronounced WV boundary.
The recognition of the frontal system over central Europe proves to be harder with WV6.2 imagery. The occluded part of the system is quite enhanced and appears as bright and white in WV over the Baltic Sea, Denmark and the North Sea. Cyclonically curved over UK, the Gulf of Biscay into France and further to Belgium a dry band can be seen. On the tip of this dark band some increased convectivity is seen over the Netherlands. A deformation zone can be recognised over Spitsbergen and Skandinavia. A bright cell is seen over Switzerland indicating some convective development that should be looked at in future timesteps. More interesting are the convective cells that have emerged over Belarus and Ukraine. They develop on a pronounced WV boundary.
Airmass RGB
The frontal system covering central Europe is easier to recognise with these set of airmass images. The occlusion with some convective cells embedded, is found over Poland, Germany and the Netherlands. Further to the south the cold front is recognised as the low level cloudiness pictured in blue covering Eastern France and Switzerland. On the cyclonic as well on the anticlyclonic side of the frontal system two areas of deepening (pictured here as puprle) are recognised. Most convection will start on the boundaries of these WV features. Further east, ahead of the frontal sytem on the border between Belarus and Ukraine an area with high PV values is recognised (appears as red). The cyclogenesis observed here is accompanied by convection as some cells emerged.
The frontal system covering central Europe is easier to recognise with these set of airmass images. The occlusion with some convective cells embedded, is found over Poland, Germany and the Netherlands. Further to the south the cold front is recognised as the low level cloudiness pictured in blue covering Eastern France and Switzerland. On the cyclonic as well on the anticlyclonic side of the frontal system two areas of deepening (pictured here as puprle) are recognised. Most convection will start on the boundaries of these WV features. Further east, ahead of the frontal sytem on the border between Belarus and Ukraine an area with high PV values is recognised (appears as red). The cyclogenesis observed here is accompanied by convection as some cells emerged.
Geopotential Height 1000 hPa
The image shows a frontal system covering Western Europe. The occluded part of this system, which lies over the Baltic Sea, Denmark and the North Sea is characterised by an elongated surface low. The cold front part is harder to distinguish as it is contained of low clouds. It is found over Switzerland and Southern Germany and is characterised by a surface ridge.
The image shows a frontal system covering Western Europe. The occluded part of this system, which lies over the Baltic Sea, Denmark and the North Sea is characterised by an elongated surface low. The cold front part is harder to distinguish as it is contained of low clouds. It is found over Switzerland and Southern Germany and is characterised by a surface ridge.
Geopotential Height 300 hPa
A pronounced upper level low is found over Southern England, with its trough-axis over France the orientation and position of the cold front is easier. Up north the warm front part of the synoptic system is reflected by a small upper level ridge.
A pronounced upper level low is found over Southern England, with its trough-axis over France the orientation and position of the cold front is easier. Up north the warm front part of the synoptic system is reflected by a small upper level ridge.
Temperature Advection 700 hPa
The occlusion cloud band (Sweden, Denmark and North Sea) and the warm front cloudband (Baltic States) are superimposed by warm air advection.
Several cells can be seen embedded in this frontal band, they are marked by WA maxima indicative for the cold cloudtops.
The cold front is found in this image over Switzerland and Southern Germany and is characterised by a CA maximum. Ahead of it a tongue of warm air advection is found.
The occlusion cloud band (Sweden, Denmark and North Sea) and the warm front cloudband (Baltic States) are superimposed by warm air advection.
Several cells can be seen embedded in this frontal band, they are marked by WA maxima indicative for the cold cloudtops.
The cold front is found in this image over Switzerland and Southern Germany and is characterised by a CA maximum. Ahead of it a tongue of warm air advection is found.
Divergence 700 hPa
Striking at this instance is the region with convergence over the cold front. Ahead of this front already outflow and divergence is observed.
Striking at this instance is the region with convergence over the cold front. Ahead of this front already outflow and divergence is observed.
Divergence 850 hPa
Divergence 925 hPa
By using the modelfields of Aladin the divergence/convergence at 925 hPa is pictured. The convergence is presented by the dashed lines. Within the cold front a region with convergence is recognised. Its this region that will during the day further enahce and also show some convective development. Concentrating back on the case study, also ahead of the frontal system regions with convergence can be observed which at this stage already mark the orientation of the prefrontal convergence line.
By using the modelfields of Aladin the divergence/convergence at 925 hPa is pictured. The convergence is presented by the dashed lines. Within the cold front a region with convergence is recognised. Its this region that will during the day further enahce and also show some convective development. Concentrating back on the case study, also ahead of the frontal system regions with convergence can be observed which at this stage already mark the orientation of the prefrontal convergence line.
Wind 700 hPa
Wind 850 hPa
Wind 925 hPa
By using the modelfields of Aladin the windfields in the boundary layer at 925 hPa are studied. The direction of the wind is marked by the arrows. At this timestep (some 8 hours before the convection starts!) the prefrontal convection line is already recognised with converging motions over Northern Italy, Austria (red circles) and further north in the Czech Republic and Poland.
By using the modelfields of Aladin the windfields in the boundary layer at 925 hPa are studied. The direction of the wind is marked by the arrows. At this timestep (some 8 hours before the convection starts!) the prefrontal convection line is already recognised with converging motions over Northern Italy, Austria (red circles) and further north in the Czech Republic and Poland.
TFP and RTP
In the image the thermal front parameter (blue) and the relative topography (green) are superimposed on IR10.8 imagery. The location and orientation of the frontal system is easier with these parameters. The warm front can now be recognised over the Baltic Sea and Lithuania, further west the Occlusion (hardly any TFP) over Sweden, Denmark and the North Sea. The Cold Front is also well observed with a pronounced TFP maximum. Ahead of this front a second TFP maxima is found where the future convection line will develop. The thermal advection induced by the rising motions is most likely causing this strong signal in the TFP.
In the image the thermal front parameter (blue) and the relative topography (green) are superimposed on IR10.8 imagery. The location and orientation of the frontal system is easier with these parameters. The warm front can now be recognised over the Baltic Sea and Lithuania, further west the Occlusion (hardly any TFP) over Sweden, Denmark and the North Sea. The Cold Front is also well observed with a pronounced TFP maximum. Ahead of this front a second TFP maxima is found where the future convection line will develop. The thermal advection induced by the rising motions is most likely causing this strong signal in the TFP.
Showalter Index
The IR image is now overlayed with the Showalter index. This index gives a good indication where the atmosphere is unstable and where convective development may be expected. Showalterindeces between 1 and 4 give the indication that thunderstorm are possible but that a trigger is still needed. From this treshold downward the chance on thunderstorms increase. Values under –3 are associated to very heavy thunderstorms. In this set of images the treshold of Showalter Index = 0 is pictured using the pink line. This allow an easy discrimination of the potential convective areas. Such an area can be seen here stretched over central Europe. South of the Alps (a region where the first signs of prefrontal convergence will be seen) the SI is even below –3.
The IR image is now overlayed with the Showalter index. This index gives a good indication where the atmosphere is unstable and where convective development may be expected. Showalterindeces between 1 and 4 give the indication that thunderstorm are possible but that a trigger is still needed. From this treshold downward the chance on thunderstorms increase. Values under –3 are associated to very heavy thunderstorms. In this set of images the treshold of Showalter Index = 0 is pictured using the pink line. This allow an easy discrimination of the potential convective areas. Such an area can be seen here stretched over central Europe. South of the Alps (a region where the first signs of prefrontal convergence will be seen) the SI is even below –3.
ThetaE 850 hPa
A second way of describing the stabilty of the atmosphere is by making use of Theta E fields at 850 hPa
High Theta-E values are an indication for instability. A Theta-E ridge or tongue is often the burstpoint for convective activity.
A pronounced Theta-E maximum is found over the Czech Republic. Its instability is reflected in IR by a large MCS. Further South a secondary maximum gives indication of an unstable atmosphere. (un)fortunately this is not seen in IR10.8, maybe because of a strong cap.
A second way of describing the stabilty of the atmosphere is by making use of Theta E fields at 850 hPa
High Theta-E values are an indication for instability. A Theta-E ridge or tongue is often the burstpoint for convective activity.
A pronounced Theta-E maximum is found over the Czech Republic. Its instability is reflected in IR by a large MCS. Further South a secondary maximum gives indication of an unstable atmosphere. (un)fortunately this is not seen in IR10.8, maybe because of a strong cap.
Severe Convection RGB
The Severe Convection RGB, which is also discussed thoroughly in the MSG interpretation guide, is suitable for the detection of convection and it is able to discriminate between young and old convective cells.
The Severe Convection RGB, which is also discussed thoroughly in the MSG interpretation guide, is suitable for the detection of convection and it is able to discriminate between young and old convective cells.
The interpretation of the colours goes according to:
- red: Deep precipitating clouds contained of large ice particle
- yellow: Cbs with severe weather and strong updrafts; small ice particles OR thick high level lee cloudiness.
- darkred: Thin cirrus; large ice particles
- purple: Thin cirrus cloud; small ice particles
- blue: Thin to no clouds.
With this information it can now be derived that the occluded part of the frontal band covering central Europe is consistant of deep precipitating high level clouds. Especially over the Baltic Sea isolated convective cells are recognised. Within the cold front part which is covering Switzerland and France low level waterclouds are recognised. Embedded some yellow sports that can be the first signs of prefrontal convergence.
Further south over the Swiss Alps also some yellow spots are seen. In following timesteps we will see that these clouds are not the deep precipitating clouds with small ice-particles but rather Lee Clouds.