by Maria Putsay, Ildikó Szenyán (Hungarian Meteorological Service) and Jochen Kerkmann (EUMETSAT)Jump to images
On 20 May 2008 a severe convective storm developed over Hungary causing heavy precipitation, strong winds and hail (2-5 cm). Tornado, funnel clouds were reported. Flash floods occurred in some places. A fishing lake damn broke causing additional floods in the surrounding area. The storm system developed rapidly and by late afternoon it had spread to Romania, also causing hail, flash floods and damage in several places.
The Hungarian Meteorological Service gave the highest level of alarm the day before, forecasting the possibility of tornados. MeteoAlarm (Alerting Europe for Extreme Weather) and Estofex (European Storm Forecast Experiment) also issued severe warnings for Hungary (see MeteoAlarm warning, PNG, 61 KB and Estofex storm forecast, PNG, 129 KB).
The top image below shows the enhanced Meteosat-9 IR10.8 image of 11:45 UTC. Brightness temperatures below 240 K are shown in colours, while values above 240 K are shown in black. The image shows prominent examples of so-called "cold-ring shaped storms" over Hungary and Serbia. As discussed in the paper from Setvak et al. (2008, PDF, 1711 KB), long-lived cold-ring shaped storms should receive special attention from forecasters given their high chance of producing severe weather. In this case, the cold-ring storm over Hungary had a lifetime of about two hours. It should be noted that the cold-ring indicator is only one of many possible satellite indicators for severe weather: if many of them come together then the likelihood of severe weather increases. In this case, at least 11 indicators for severe weather can be listed:
- cold-ring shape (enhanced IR10.8 image)
- unstable environment (GII product)
- explosive growth (IR10.8 and HRV image)
- cold cloud tops (IR10.8 image)
- strong overshooting of the tops of convective cells (HRV image and WV6.2 - IR10.8 difference)
- long-living storm system (more than 10 hours, HRV and IR10.8 image)
- right-moving storm (HRV and IR10.8 image)
- above-anvil plume (HRV image)
- small ice particles (Convection RGB product, IR3.9r effective radius (Reff) product)
- retrieved vertical profiles of cloud particle effective radius and thermodynamic phase (T-Reff plots, see second image below)
- low-level inflow jet (HRV images)
A more detailed discussion of this case and of the indicators listed above can be found in the paper from Putsay et al. (2008, PDF, 1463 KB) and the poster from Schipper et al. (2008, PPT, 3918 KB).
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