Lightning Detection and airmass composite, Time Sequence: 1h, 29 February to 01 March 2008     

This chapter presents the lightning detection during the last 60 min in combination with the airmass-RGB. The meaning of the colouring of the lightning markers is given in each image. For more information about the saellite images' colouring click upon legend or click upon the key symbol (above).

By clicking through the time steps the movement and development of the thunderstorms can be observed.

We will investigate the position of the lightning detection in relation to the airmass composite. This will give us information about dynamical processes yielding convection during the passage of the cold front and succeeding convective line. The lightnings shows us the convective line's intensity and velocity.

The airmass-RGB reveals over Scotland and the North Sea a purple area of high PV and an overrunning jet. The latter can be seen from the pink-brownish coloured clouds over the Southeast North Sea to North Germany. Because this area moved fast to the east-southeast dynamical forcings in its forefield are likely.

All structures moved fast to South-Southeast.

The fast movement continued. Some lightings over North England were detected about 30 to 40 minutes before (near the transition of purple to blueish areas).

In the meanwhile most parts of the convective line came to the left exit region of the jet streak which extended from Scotland to North Germany. The RGB shows a corresponding transition from bluesih to purple colour. It is likely that showers/thunderstorms will develope in the convective line (near the transition from blue to purple).

Some recent lightnings (during the last 10 minutes, red) occured near the Dutch Coast.

During the last hour the lightnigns activity increased (373 detections, almost all over the Northeast exit of the Channel to the Dutch coast) and moved with more than 100 km/h to southeast.

The number of lightning detections increased to 1374 and the velocity to almost 150 km/h. We see a good correspondence to the transition from the blue to the purple area. The lightnings more to the northeast took place in the left exit of the jet, i.e., were influenced by positive vorticity advection (PVA).

The thunderstorms became more line-orientated. The entire cluster was influenced by PVA (left exit of the jet and in the front of the upper trough's axis). The lightnings activity continued increasing to 1602 detection. The velocity remained high with about 150 km/h.

During the last hour 2320 lightnings were detected and we see a clear line structure that extended from Central Germany to the southwest.

This image reveals an excellent example of a convective line. The lightning activity increased again to 3370 detections.

Also this image is an instructive example of the airmass RGB's potential. We see cloud structures (among other the convective line), the shape of the trough, the left exit of the jet and the corresponding position of the convective line. Finaly, this image reveals the area of high PV.

The lightning intensity continued increasing (to 6298 detections during the last hour). However, the convective line moved a bit slower (about 120 km/h).

8469 lightnings were detected and the movement's speed remained unchanged at about 120 km/h.

The lightning activites reached its maximum (12942 detctions during the last hour!). The convective line' velocity remained unchanged (about 120 km/h). The convective line reached an impressing length of about 600 km!

Again, the potential of the airmass RGB should be demonstrated: We see the convective line and we see that recent lightning (red markers) occured at the frontal part of the trough-shaped purple area, i.e., in front of the trough's axis (trough), the position of the recent lightnings was at the left exit of the jet. Finaly, we see the most intense activities at the frontal part of the area of high PV that moved very fast to the southeast, i.e., caused PVA.

The lightning activity started weakening (11687 detections). We see that in the lee of the Bavarian Forrest lightning stopped about 45 minutes ago. However, the other parts remained very active and the convective line's speed was still about 120 km/h.

During the last hour the convective line became less active (3860 lightnings were detected). From the colours, we see that almost no lightning occured during the last about 15 minutes in the west part of the convective line. Also the line structure became less clear.

Whereas the convective line exihibited active lightning over East Austria and Slovakia no lightning was detected further to the west and during the last 30 minutes.

The reasons for that can be seen from different images. The geopotential 300 hPa shows that the west part of the convective line was near the trough's axis partly behind it yielding less positive vorticity advection (PVA). From the wind speed in 300 hPa we see that the convective line was not in the left exit of the jet (again less PVA). From the PV in 310 K we clearly see that only the central and east parts of the convective line was in front of the approaching PV-maximum, yielding PVA. However, further to the west we do not see high PV-values.

The zone of intense lightning crossed the eastern parts of the Alps.

The east part of the convective line remained still active and continued fast moving to southeast (still 100 to 120 km/h).

A few lightnings occured near the trough's axis over South Germany. The lightning in connection with the convective line moved with 120 km/h.

The area of lightning crossed Hungary and kept on moving with 100 to 120 km/h. Over northern Italy we see an intense blue area in connection with Foehn.

The lightnings activity decreased. On the other hand, we should keep in mind that with increasing distance from Germany the lightning detection becomes more and more unreliable.

During only 15 hours (from 1st March 02 UTC to 17 UTC) the convective line covered a distance of about 1600 km, equivalent to an average velocity of 110 km/h!

Only a few lightnings were detected.