Severe convection of 30 May 2005 as observed from Prague

by Martin Setvak and Petr Novak (CHMI)

The storms of 30 May 2005 are very interesting from satellite perspective and spectacular on ground-based photos. They caused moderate damage at many places over the Czech Republic - mainly by heavy rain and hail, with few places hit by wind gusts. No tornado was reported on that day. Since the case is very interesting from multispectral point of view, it will be investigated in detail, in comparison with radar and soundings data. Here we present several ground-based images of one of these storms (very likely a supercell storm), and radar observations from the Czech radar network.

Ground-based Images 11:48 UTC Full Resolution (480 KB) Source: Martin Setvak 11:50 UTC Full Resolution (315 KB) Source: Martin Setvak 11:51 UTC Full Resolution (299 KB) Source: Martin Setvak 11:53 UTC Full Resolution (477 KB) Source: Martin Setvak

The images above were taken by older classic film camera, Praktica BX-20, with Flektogon 2.8/28 lens and Fujichrome Sensia 100 slide film. Next, these were scanned by Nikon LS-2000. The slides were shot from roof of the Radar and Satellite Department building of the Czech Hydrometeorological Institute at Praha, Libus.

See also the animation (MPEG1, 4575 KB, source: Martin Setvak) of this storm, taken by Creative WebCam Live! Ultra at 1 second intervals, between 11:25 and 12:15 UTC from the same location.

On the images above notice the very thin "shell" layer which developed on the upwind side of the storm top after 11:50 UTC. It is not quite clear if this phenomenon is composed of ice particles (then it could be assigned as pileus cloud) or if it is visualised by higher concentration of water vapor. If composed of ice particles, these are likely to be very small and therefore would contribute to overall increased NIR (1.6 and 3.9 µm bands) reflectivity.

Finally, individual PPI's from the Brdy radar for 11:30 UTC (storm marked above by arrow) show radar features resembling a hook echo (see image composite, 106 KB, source: CHMI). However, in this case it is not quite certain if it is indeed a supercellar hook, or rather a structure resulting from spatial arrangement of two splitting close-by cells. Ten minutes before and after this scan, the feature was not detectable.

Meteosat-8 HRV images of the storm shown above. The 11:45 UTC image corresponds to the 11:53 UTC photo above. The white arrow points to the south part of the storm shown on the photos. Notice the faint plume on the 12:15 UTC image, streaming north from the storm's core. Similar plumes can be seen also above two other storms. Met-8, 30 May 2005, 11:45 UTC Channel 12 (HRV) Met-8, 30 May 2005, 12:15 UTC Channel 12 (HRV)

Radar view of the storms and their development (maximum reflectivity product). The black arrow points at the storm shown above, origin of the arrow depicts  the location from which the images above were taken. Animation Czech Radar Network (10:00-22:00 UTC, GIF, 10714 KB) Animation Brdy-Praha Radar(10:00-14:00 UTC, GIF, 2798 KB) Zoom Animation Brdy-Praha Radar (10:00-14:00 UTC, GIF, 1111 KB) Lightning data from CELDN network (15:20-15:30 UTC, PNG, 275 KB)

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