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An Explosive Convection over Europe with 8-Minute Tornado Incident in Poland on July 20, 2007

Jan Parfiniewicz1 and Piotr Barański2

1. Institute of Meteorology and Water Management, Poland

2. Institute of Geophysics, Polish Academy of Sciences, Poland


Abstract: On July 20, 2007, an explosive convection weather event has affected a number of European countries: England, Germany, Poland and Ukraine. Severe storms caused extreme floods (Britain and Ukraine) and damaging winds, with tornado in Poland. The case has been broadly discussed, especially in British and Polish media, often suggesting its climate change origin. Numerous works have been done to examine the case. We present a detailed analysis of supercell dynamic development connected with tornado incident and the time and space behavior of its lightning activity. For this purpose, we have used reflection data from Doppler radars to obtain, as realistically as possible, the history of 3-dimensional evolution of the convective complex which started to develop over south Poland. The COSMO model i.e., computer simulations with different grid resolutions has been used, with grid step squeezed up to 2.8 km, to recognize relative impact of tornado on the multi-scale dynamic system. We have also included to our analysis the examination of the observed lightning rate changes of particular convective complexes before and after the supercell aggregation. On the other hand, locations of positive and negative return strokes of cloud-to-ground flashes (RS+ and RS), and intracloud discharges (IC) given by the SAFIR/PERUN system in the supercell area revealed their specific clustering co-located with precipitation/hail shafts and previous widespread IC lightning activity followed by grouped CG± flash strokes. This paper refines the documentation addressed to Polish reader and finally gives insight into 3D wind structure by applying the Doppler radial retrieval.

Key words: Thunderstorm, supercell, tornado, hail gush, lightning flash rate, lightning detection, Doppler radar.
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