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Using ALARO and AROME numerical weather prediction models for the derecho case on 11 August 2017

Kolonko Marcin, Szczęch-Gajewska Małgorzata, Bochenek Bogdan, Stachura Gabriel, Sekuła Piotr

Meteorology Hydrology and Water Management. Research and Operational Applications

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2022

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Vol. 10, Iss. 2

88--105

EN

On average, a derecho occurs once a year in Poland while bow echoes happen several times per year. On 11 August 2017, severe meteorological phenomena were observed in Poland, including extremely strong wind gusts. We focused especially on the convective windstorm of a derecho type which occurred on that date in northern and north-western Poland. A rapidly moving mesoscale convective system (MCS) resulted in a bow echo, a mesoscale convective vortex (MCV), and finally fulfilled the criteria for a derecho. To establish whether our operational models in the Institute of Meteorology and Water Management, National Research Institute (IMGW-PIB) could reproduce a derecho of such intensity as that of 11 August 2017, the results from two mesoscale numerical weather prediction models were analyzed. The Application of Research to Operation at Mesoscale (AROME) and the ALADIN & AROME (ALARO) models were applied in the non-hydrostatic regime. We also examine how models differ with respect to mesoscale convective system drivers (such as vertical wind shear and convective available potential energy) and representation of deep convection (e.g., vertical velocities, cold pool generation). Forecasts are compared with observations of wind gusts and radar data. Severe weather phenomena, such as rear inflow jet and cold pool, were predicted by both models, visible on the maps of the wind velocity at 850 and 925 hPa pressure levels and on the map of air temperature at 2 m above the ground level, respectively. Relative vorticity maps of the middle and lower troposphere were analyzed for understanding the evolution of MCV.

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The impact of initial and boundary conditions on severe weather event simulations using a high-resolution WRF model. Case study of the derecho event in Poland on 11 August 2017

Figurski Mariusz J., Nykiel Grzegorz, Jaczewski Adam, Bałdysz Zofia, Wdowikowski Marcin

Meteorology Hydrology and Water Management. Research and Operational Applications

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2022

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Vol. 10, Iss. 2

60--87

EN

Precise simulations of severe weather events are a challenge in the era of changing climate. By performing simulations correctly and accurately, these phenomena can be studied and better understood. In this paper, we have verified how different initial and boundary conditions affect the quality of simulations performed using the Weather Research and Forecasting Model (WRF). For our analysis, we chose a derecho event that occurred in Poland on 11 August 2017, the most intense and devastating event in recent years. High-resolution simulations were conducted with initialization at 00 and 12 UTC (11 August 2017) using initial and boundary conditions derived from the four global models: Global Forecast System (GFS) from the National Centers for Environmental Prediction (NCEP), Integrated Forecast System (IFS) developed by the European Center for Medium-Range Weather Forecasts (ECMWF), Global Data Assimilation System (GDAS) and ERA5. For the last, we made separate calculations using data at the pressure and model levels. The results were evaluated against surface and radar data. We found that the simulations that used data from the GDAS and GFS models at 12 UTC were the more accurate, while ERA5 gave the worst predictions. However, all models were characterized by a low probability of detection and a high number of false alarms for simulations of extreme precipitation and wind gusts.

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Synoptic conditions of the derecho storm. Case study of the derecho event over Poland on August 11, 2017

Wrona Barbara, Mańczak Piotr, Woźniak Anna, Ogrodnik Michał, Folwarski Michał

Meteorology Hydrology and Water Management. Research and Operational Applications

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2022

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Vol. 10, Iss. 2

8--25

EN

This study presents a comprehensive synoptic analysis of one of the most violent storms recorded in recent years in the northwestern part of Poland, which occurred on August 11, 2017. Its development took place ahead of a waving cold front in the tropical air mass, downstream of the upper-level trough. The thunderstorms formed over Lower Silesia in the afternoon and moved towards Gdańsk Pomerania to occur over the Baltic Sea after midnight on August 12, 2017, where they gradually disappeared. As the thunderstorms moved through this area, they ranged from single convective cells and unorganized multicell storms through supercell thunderstorms to mesoscale convective systems in the form of bow echo squall lines and the mesoscale convective vortex (MCV). The convective system, evolving over time, fulfilled the derecho criteria. Its development was related to the presence of both the upper and mid-level jet stream, which supported the formation of a strong rear inflow jet (RIJ) in the rear part of the convective system, being one of the main factors generating the formation of a bow echo squall line with strong wind gusts. The maximum wind gusts recorded on August 11, 2017, are among the highest in the history of Polish measurements and amounted to 42 m/s in Elbląg, 36 m/s in Chrząstów, 35 m/s in Gniezno, and around 30 m/s at several other stations.

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Derecho radar analysis of August 11, 2017

Łuszczewski Hubert, Tuszyńska Irena

Meteorology Hydrology and Water Management. Research and Operational Applications

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2022

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Vol. 10, Iss. 2

26--37

EN

This paper presents an analysis of the derecho phenomenon that occurred over Poland on August 11, 2017. The storm caused 6 fatalities, 39 injuries (Mańczak et al. 2022), and some of the greatest damage in the history of Polish forestry. Our study is based on radar meteorology and measurements from the Polish POLRAD radar network, and intended for advanced meteorologists with good knowledge of radar measurements. The research used both standard and specialized radar products as well as classic and Doppler scan data. The Doppler velocity products were especially useful for showing the characteristics of the storm. The analysis was mainly based on data from two radars: Poznań and Gdańsk, but the composite maps, consisting of data from more than one radar, were also analyzed. The derecho complex developed from unorganized thunderstorm cells over SW Poland and moved toward the NE. The various stages of the evolution of the system are presented and analyzed, accounting for the formation of a SC, the development of a rear inflow jet (RIJ), the split of the entire system, and the appearance of the bow echo signature. Significant factors affecting the scale of the wind damage were: (1) the extensive mesocyclone which evolved to the mesoscale convective vortex (MCV), and (2) a strong rear flank downdraft interacting with the rear inflow jet (RIJ).

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Proposed classification for all types of wind storms in Poland

Chmielewski T., Nowak H.

Archives of Civil Engineering

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2020

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Vol. 66, nr 4

183--200

EN

International scales describing the intensity of tornadoes are investigated along with reports from the Polish Government Security Centre on all types of wind storms in Poland. Then, collected tornado reports for the years 1899-2019 in Poland, a set of the annual maximum gust wind speeds measured at 39 meteorological stations from 1971 to 2005 (35 years), descriptions of Poland’s strongest wind storms in the 21st century, estimating the risk of significant strong and extreme winds in Poland, and classification of maximum wind speeds by Lorenc (2012) are presented. Based on these data, i.e. measured and estimated wind speeds, this paper proposes two separate intensity scales to categorize synoptic, thunderstorm, and downslope winds (in the Tatra and Karkonosze regions), derechos, tornadoes, and downbursts, i.e. all types of wind storms. These scales are simpler than the one put forward by Lorenc (2012). These two scales cover a range of maximum wind speeds from 20 to 90 m/s. This proposal is only applicable to Poland. Other countries may determine whether it applies to them.

PL

Różnego rodzaju burze wiatrowe w Polsce każdego roku stanowią potencjalne duże zagrożenie strat finansowych w gospodarce, zdrowia i życia ludzkiego w naszym kraju. W niniejszym artykule przedstawiono: raport Rządowego Centrum Bezpieczeństwa (RCB) o potencjalnych zagrożeniach naturalnych w Polsce, międzynarodowe skale opisujące intensywność trąb powietrznych, badania dotyczące liczności trąb powietrznych w latach 1899-2019 w Polsce, zestaw rocznych maksymalnych prędkości wiatru w porywach mierzonych na 39 stacjach meteorologicznych w latach 1971-2005 (35 lat), opisy najsilniejszych burz wiatrowych w Polsce w XXI wieku, oszacowanie ryzyka silnych i ekstremalnych wiatrów w Polsce i klasyfikację maksymalnych prędkości wiatru w Polsce i skutki ich działania, zaproponowaną w 2012 roku przez Lorenc [10]. Na podstawie powyższych danych zaproponowano dwie osobne skale klasyfikacji maksymalnych prędkości wiatru i skutki ich działania dla wszystkich burz wiatrowych, tj.: synoptycznych burz wiatrowych, burz wiatrowych lokalnych, burz w rejonach górskich (wiatru halnego w rejonie Tatr lub fenu w rejonie Karkonoszy), trąb powietrznych, szkwałów i rozległych burz wiatrowych typu derecho. Te dwie skale obejmują zakres maksymalnych prędkości wiatru od 20 do 90 m/s.

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Estimation of critical wind speed on the basis of roof blow-off

Chmielewski T., Kaleta B., Nowak H.

Archives of Civil Engineering

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2020

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Vol. 66, nr 3

391--405

PL

W dniach 11-12 sierpnia 2017 r. nad Polską przeszła rozległa burza wiatrowa. Cała burza obejmowała obszar około 540 km od Wrocławia, przez Poznań, Bydgoszcz, wzdłuż Gdyni i Gdańska oraz część Wybrzeża. Z dużą siłą wiatru przeszła przez trzy województwa: Wielkopolskie, Kujawsko-Pomorskie i Pomorskie. Pomierzone prędkości wiatru osiągnęły 130 km/h, powodując duże zniszczenia na swojej drodze, a w jednej stacji synoptycznej, tj. w Elblągu prędkość wiatru przekroczyła 150 km/h. Maksymalne prędkości wiatru zostały pomierzone w następujących miejscowościach: Chojnice: 31.2 m/s (112 km/h), Gniezno: 34.8 m/s (125 km/h), Chrząstowo/Noteć: 36.0 m/s (130 km/h), Elbląg: 42,0 m/s (151 km/h). Ścieżka przejścia burzy była w przybliżeniu liną prostą, miała ponad 400 km długości i w trzech miejscach oddalonych około 70 km wiatr wiał z prędkością 100 km/, czyli burza spełniała kryteria burzy „derecho”. Burza wiatrowa spowodowała ofiary ludzkie i ogromne straty materialne opisane w pracy [8]. Celem artykułu jest oszacowanie krytycznej prędkości wiatru w zdarzeniu zerwania dachu jednopiętrowego ceglanego budynku podczas burzy wiatrowej w dniu 11 sierpnia 2017 r. W tym celu obliczono ciężar konstrukcji i pokrycia dachu oraz oszacowano siłę połączenia między murłatami i ściankami kolankowymi. Wzajemne porównanie obu tych sił umożliwiło obliczenie krytycznej prędkości wiatru, która okazała się znacznie większa od wartości pomierzonych na stacjach meteorologicznych.

EN

Types of wind storms in Poland and examples of economic damage, threats to human life and health caused by two extreme wind events are presented. Then, a house with the roof blown-off during the derecho wind storm in Poland on August 11-12, 2017, is considered. Based on the rafter framing of the house, i.e. wooden roof structure elements and roof covered, the weight of the roof is calculated. Two cases of the strong connection between rafter plates and knee walls are estimated. With the estimation of connection strength between rafter plates and knee walls, it was possible to calculate the total force required to blow-off the roof of the house. Next, an aerodynamic force acting on the house is calculated using pressure coefficients for a low-rise house with a gable roof. The pressure coefficients were taken from the Tokyo Polytechnic University aerodynamic database. The aerodynamic force acting on the roof blown-off was calculated for a low-rise building with a gable roof for similar ratios for length, width, and height. Three wind directions, for the unknown orientation of the building, were considered, i.e. the wind direction perpendicular, parallel, and oblique to the gable wall. By comparison, the aerodynamic force with the total force required to blow-off the roof of the house, it was possible to calculate the critical wind speed needed for the roof blown-off. This wind speed is much bigger than measured by meteorological stations on the path of the derecho.

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Skutki gwałtownej burzy wiatrowej z sierpnia 2017 r. w Polsce

Pistol A., Flaga A.

Inżynieria i Budownictwo

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2018

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R. 74, nr 10

508--513

PL

Jedna z najsilniejszych odnotowanych nawałnic miała miejsce 11 i 12 sierpnia 2017 r. nad terenem środkowej Polski. Na stacji meteorologicznej Elbląg–Milejewo odnotowano rekordową do tej pory na terenie Polski prędkość porywu wiatru w tej klasie zjawisk meteorologicznych, wynoszącą ponad 42 m/s. Ze względu na obszar oddziaływania, skalę zniszczeń, długość trwania i prędkości podmuchów nawałnicę można sklasyfikować jako derecho, czyli długotrwałą gwałtowną burzę wiatrową.

EN

On 11th and 12th of August 2017 central Poland was subject to one of the most devastating storms ever recorded in this area. At the weather station in Elbląg-Milejewo a record gust speed in Poland history has been recorded for this class of meteorological phenomena that exceeded 42 m/s. Considering the affected area, extent of damages, duration and gust speeds, the storm can be classified as a derecho, a sustained torrential gusty wind storm.