Severe Storms RGB Time Sequence: 30min, 01 March 2008      

The RGB "Severe Storms" which is also discussed thoroughly in the MSG interpretation guide, is suitable for the detection of deep convection and enables us to discriminate between young and active and old and decaying convective cells.

The interpretation of the colours goes according to:

• Red: deep precipitating clouds containing large ice particle
• Yellow: Cbs with severe weather and strong updrafts; small ice particles or thick high level lee cloudiness.
• Dark red: thin cirrus; large ice particles
• Purple: thin cirrus cloud; small ice particles
• Blue: thin clouds or cloud free areas

With this RGB it is possible to perform more detailed diganostics. An important information in addition to the colour are the areas' shape and its position in relation to the airmass distribution. A convective cell with high potential for intensification exhibits a rounded shape. If the position of the yellow spot is at the "warm edge" of a cell we have to expect a higher probability for cell intensification. The images will be shown in 30-minutes intervals.

The convective band extended from the Baltic Sea to West Germany. We see only dark red clouds, i.e., relatively big ice particles.

Note: You can always click on the in the header to bring up the RGB-key.

Whereas we recognise over Austria yellow areas (equivalent to small ice particles) we have to consider also the shape. If we do not find a spot a convective cell with strong updraft is not likely. This is more the case for some cells over Romania (right edge of the image).

Surprising is that no hints to strong updrafts come for the convective line over Middle Europe. The name of this RGB is "Severe Storms". This means that it is best applicable for deep summer convection. This convective line belongs more to the category "Severe winter convection". Typically, we do not observe very low cloud top temperatures (below -60°C, in this case it was "only" -45°C).

Only a few yellowish spots developed at the frontal edge (South - Southwest Germany).

Only a few yellowish spots over Southwest Germany can be found.

We find some hints to a chain of convective cells (yellowish spots) with some potential to intensify and strong updraft over South Germany near 10°E.

The general situation did not change. We see one cell with a more intense updraft (according to the interpretation rules of this RGB) near the Black forrest.

The image reveals a few very small and yellow spots near the Danube (South Germany).

A chain of yellow spots developed at the frontal edge of the convective line.

This image and some of the following reveal a good example of lee clouds. Typically, these clouds develop during a Föehn-situation in the lee of the Alps. Also these clouds contain a lot of small ice particles yielding the bright yellow colour. However, there are no hints to convection because the bright yellow area is too big and too smooth.

Over South Germany a few convective cells can be identified. The cirrus shield due to lee effects became more apparent. A similar effect happened at the lee of the Vosges.

This image exhibits some convective cells with strong updrafts in the west edge of the convective line (Austria). We still see the lee clouds near the Vosges and south of the Alps.

The convective line arrived the Alps and weakened (almost no yellow spots). The lee effects continued.

The convective line moved slower to the southeast, probably due to stau effects. We see some yellow spots (most active cells). The lee clouds moved slowly to the southeast, too. That means that the fast streaming (150 kt) is penetrating through the clouds and in the maximum height of the gravitiy waves we see the clouds. The clouds itselves remain more or less at the same position. Northwest of the yellow area we we see a bigger blueish area of almost no cloudiness (NE-Italy).

Whereas the lee effects from the Vosges weakened the effects due to the Alps continued.

An interesting detail can be seen over Switzerland and parts of Austria. This chain of small yellow spots is probably not connected to convective cells with strong updrafts. These structures are probably connected to local lee effects of high mountains or mountain massifs.

No significant changes occured during the last 30 minutes. South of the Central Massif (South France) we find some lee clouds.

The lee clouds over North Italy and South France remained. However, over Switzerland the lee clouds seem to weaken.

This image shows lee clouds only over North Italy. However, the lee effects weakened over the Alps and near the Central massif.