Surveying and forecasting the 24 June violent tornado in southeastern Czechia

Result code in IS VaVaI

<a href="https://www.isvavai.cz/riv?ss=detail&h=RIV%2F00020699%3A_____%2F22%3AN0000121" target="_blank" >RIV/00020699:_____/22:N0000121 - isvavai.cz</a>

Result on the web

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DOI - Digital Object Identifier

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Result language

angličtina

Original language name

Surveying and forecasting the 24 June violent tornado in southeastern Czechia

Original language description

Contribution at 30th Conference on Severe Local Storms, Santa Fe, USA, 24.10.-28.10.2022. Abstract: In the evening of 24 June 2021, an F4 tornado affected southeastern Czechia. It damaged 1200 buildings, 180 of which had to be demolished, and caused 6 fatalities and approximately 200 injuries. The tornado lasted 40 minutes, crossing 6 settlements while producing a 27.1 km long damage path. The width of the damage path was extreme for European standards. In the beginning, the swath was at least 2500 m wide with an 520 m wide wind swath in which damage of F2 or higher occurred in the first village that was hit. Isolated instances of F4 damage were noted in 3 villages with the destruction of well-constructed brick walls and significant debarking of trees. A damage map of the tornado is shown along with examples of high-end damage inflicted to traditional central-European residences. We discuss the challenges associated with the application of the International Fujita scale as well as the operational difficulties we encountered when surveying such a large area. The event was not well forecast even by the expert forecasters present at the ESSL Testbed 2021. Although the environment was clearly conducive for supercells capable of very large hail with high values of CAPE (> 3000 J/kg) and strong vertical wind shear (0-6 km bulk shear > 20 m/s), lower tropospheric shear was forecast to remain fairly weak by most of the NWP models with 0-1 km bulk shear < 10 m/s and 0-1 km SRH < 100 m2/s2. The fact that only one tornado (and of such a high intensity) occurred in the area despite numerous supercells present points to the importance of mesoscale modifications to the environment. We address these modifications and discuss the importance of local mesoscale boundaries and a storm merger occurring an hour prior to the tornado. The event illustrates some of the difficulties with tornado forecasting Europe. The first one is the lack of sufficient data exchange among countries. The tornado passed within 10 km of the borders of Austria and Slovakia. No exchange of automatic station surface observations and volumetric radar data between those countries likely limited the situational awareness of forecasters. While the tornado occurred over Czechia, the storm was best sampled from a Slovakian radar. Another difficulty was the aggressive filtering of doppler velocity data that masked the core of the low-level mesocyclone preventing forecasters to appreciate the intensity of the event as it unfolded. A final problem is that weather forecasting institutes did not, and still do not, include tornadoes in their severe thunderstorm warning criteria.

Czech name

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Czech description

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Type

O - Miscellaneous

CEP classification

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OECD FORD branch

10509 - Meteorology and atmospheric sciences

Project

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Continuities

I - Institucionalni podpora na dlouhodoby koncepcni rozvoj vyzkumne organizace

Publication year

2022

Confidentiality

S - Úplné a pravdivé údaje o projektu nepodléhají ochraně podle zvláštních právních předpisů