Lightning Detection 30 min Interval, Time Sequence: 27 July 2006

27 July 2006, 12.00 UTC

This chapter presents the lightning detection during the last 30 min. The colours give the time interval in which the lightning occured (see legend).

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

Compare also with the radar data presented in the next chapter.

We will investigate the position of the lightning detection in relation to the clouds in the IR image. First convective cells and recent lightning detection can be seen. When we investigate some details we find the following reasons for the combination of satellite images and lightning detection:

• The lightning occured rather often at the southwesterly flank of the clouds due to the outblowing of the cirrus to the NE (according to the upper wind). This is typically for multi cells.
• In some cases we find only grey cloud pixels near/at the lightning detection symbols. That is caused by the horizontal resolution of about 5 km of Meteosat 8 in 50°N yielding so-called mixed signals for one pixel, especially for small developing cells.
• In some cases we observe a shifting of the lightnings' positions to the South against the cloud tops due to the Meteosat view angle of about 35° at 50°N. For high extending clouds this shifting could be more than 10 km.
• In about 50°N, the nominal time of lightning detection is about 5 minutes later than the satellite pixels'detection time due to the scanning process of Meteosat 8/9. This can be relevant for fast processes.
• In some cases we find lightning detection and, however, no clouds near-by. In these cases electric sparges occurred, e.g., at overhead contact lines of trains.

27 July 2006, 12.30 UTC

30 minutes later we see much more lightning. Lightning during the last about 10 minuntes (orange, red) occured mainly at the windward side of the cells, i.e., at the western and southern part of the cells. We recognise lightning detection symbols of all colours which is equivalent to active thunderstorms during at least 30 minutes.

Lightning interval:

27 July 2006, 13.00 UTC

The amount of detected lightning further increased. Recent lightning (red) near the centre of convective complexes can be seen over northwestern Germany and at the big cell further to the South. This is a hint to super cell developments (see also IR-Enhanced).

Lightning interval:

27 July 2006, 13.30 UTC

We recognize several cloud clusters with intense lightning. West of Hamburg and South of this cell we see again recent lightning near the centre and western parts of the cirrus shields. That is again an indication for super cells.

Lightning interval:

27 July 2006, 14.00 UTC

This is an example of an advantage of the satellite image (enhanced) against the combination of lightning with IR (only grey values). Only the IR-Enhanced at 14 UTC shows near Hamburg clearly the so-called "severe right moving". Also a reduced time period for the lightning detection gives no better hints (not shown).

Lightning interval:

27 July 2006, 14.30 UTC

The following images of lightning detection clearly exhibit the formation of the squall line. The sequence of green, yellow to red symbols shows the movement of a thunderstorm. Line-oriented features are hinting at a squall line.

Lightning interval:

27 July 2006, 15.00 UTC

The squall line structure becomes clearer. Recently, lightning was detected farer to the East.

Lightning interval:

27 July 2006, 15.30 UTC

At this timestep the classical form of a squall line can be seen: A long North to South oriented line of lightning detection extending from northern to southern Germany with some new developments farer to the East. Only the symbol colours' distribution does not exhibit a continous movement to the East. (Typical for that would be for example a sequence of green, yellow, orange and red symbols).

Lightning interval:

27 July 2006, 16.00 UTC

At 16 UTC the lightning detections reveal the squall line with a sharp edge on its eastern side.

Lightning interval:

27 July 2006, 16.30 UTC

Most of the thunderstorms are connected to the squall line. However, some spots of the thunderstorms can be found again in the forefield of the squall line.

Lightning interval:

27 July 2006, 17.00 UTC

From 17 UTC on the thunderstorm activity clearly decreased. The typical structure of a squall line is not visible any longer.

Lightning interval:

27 July 2006, 17.30 UTC

Thunderstorm activity clearly decreases throughout the afternoon. The rest of the squall line can be seen from the lightning detection's line orientation.

Lightning interval:

27 July 2006, 18.00 UTC

The weakening of thunderstorm activity continued as indicated by the decreasing of lightning detection's density and increasing part of green symbols (lightning more than 20 minutes ago) in relation to other colours.

Lightning interval: