Session 8

This work focused on an exceptionally severe supercell thunderstorm that produced giant hail in the densely populated area of Gorzów Wielkopolski in Poland on 11 June 2019. The main purpose of our research was to investigate the uniqueness of this storm, as well as examine the reasons for the occurrence of a giant hail. Severe thunderstorms that occurred over eastern Germany and western Poland caused severe material losses primarily due to large hail. For the first time such an accurate inventory of 79 large hail reports on such a small area has been carried out, including the largest with a diameter of 12 cm and heaviest with a weight of 380 g. Information on large hail incidents was derived from voluntary observers and reports available in social media. Evaluation of environmental and Doppler radar data indicate that three unique aspects characterize this event. Firstly, the storm benefited from a favorable convective environment including a record-high CAPE exceeding 4000 J kg^-1 that was the highest ever measured value at a proximity rawinsonde station of Lindenberg, and the highest for this region according to ERA5 since 1950. Synoptic scale patterns indicate that a low pressure system over western France with an easterly oriented trough lead to the advection of warm and unstable air mass towards central Europe. Convective initiation in the discreet mode took place along the convergence line ahead of the approaching cold front. Large atmospheric instability and strong vertical wind shear driven by the upper tropospheric jet stream allowed convection to quickly evolve into supercells. Secondly, moisture pooling along the convergence zone led to convective initiation of 3 isolated cells that merged together. Two of them with already embedded rotation. This merger subsequently evolved into a single powerful mesocyclone that was a main cause of giant hail. Third, a supercell had the biggest intensity over a densely populated area, which led to considerable material losses, but also allowed collection of a large number of hail reports. Distribution of these reports indicates that peak hail size varied significantly on very small distances. Storm has been producing giant hail for around 20-minutes over a distance of around 10 km and was preceded by a well-developed velocity couplet, bounded weak echo region and hook-echo signatures on the Doppler radar scans.

How to cite: Matczak, P., Piasecki, K., Taszarek, M., Czernecki, B., Skop, F., and Sobisiak, A.: Giant hail in Poland produced by a supercell merger in extreme instability, 11th European Conference on Severe Storms, Bucharest, Romania, 8–12 May 2023, ECSS2023-26, https://doi.org/10.5194/ecss2023-26, 2023.

It is very important  to detect hazardous small scale weather phenomena occurred in highly populated areas because of its catastrophic damages. In order to monitor these local events and provide appropriate information about high impact weather, the Weather Radar Center of the Korea Meteorological Administration has installed the X-band radar netwGork consisting of three dual-polarization radars with the solid state power amplifier (SSPA) over the metropolitan area in October 2018. These radars are operating with three elevation angles per 1 minute and 150m gate size. 

In this study, we investigated severe weather cases that occurred in the Seoul metropolitan area by the analysis of data from the X-band weather radar observation network. The first case is  a strong convective event that led flash flood and many casualties over the central area of Seoul city within a 6-hour period in August 2022.  The second one is the tornado case that occurred in September 2020. Although it is a rare event on the Korean Peninsula, the high spatial and temporal resolution data of the X-band weather radar observation network can provide detailed characteristics of hazardous weather.  In particular, the X-Band network yielded better results compared with the S-Band weather radar observation network through the high spatio-temporal resolution.

In this study, we have found out some benefits of the X-band radar network when we explore the rapid developing small scale convective events. Since the X-band frequency has more attenuation for heavy precipitation and lose signals in wet radom condition, quality control and correction are essential to the performance of the products. Therefore, QC and quantitative estimation of heavy rainfall will be the main objectives of our future study.  

Acknowledgements:

This research was supported by the "Development of radar based severe weather monitoring technology (KMA2021-03221)" of "Development of analysis technologies for local-scale weather radar network and next generation radar" project funded by the Weather Radar Center, Korea Meteorological Administration.

How to cite: Park, J., Mo, S.-J., Gu, J.-Y., and Lee, S.: Analysis of severe weather detection in the metropolitan area of Korea using X-Band weather radar, 11th European Conference on Severe Storms, Bucharest, Romania, 8–12 May 2023, ECSS2023-35, https://doi.org/10.5194/ecss2023-35, 2023.

Weather radar is a meteorological observation equipment that can detect meso-scale meteorological phenomena as well as small-scale convective phenomena at an early stage with high temporal and spatial resolution. This study intends to introduce radar data used in meteorology into other perspectives. Although the physical meaning of radar data variables is more generally used, actual weather forecasting agencies are more sensitive to visible changes in the radar image itself. Computer vision technology is a representative way to directly utilize radar images. It produces new information by identifying and interpreting objects or situations by imitating the human visual cognitive system. In this study, convective echo changes were detected and tracked by computer vision using high temporal resolution of X-band weather radar images observed at 1-minute intervals. For convective echo detection, the background subtraction method was used, and techniques such as the median value and Gaussian filter were also used to minimize the echo detection error. The paths of the detected echoes were predicted using the Kalman filter technique. In order to classify the detected multiple convective echoes into individual objects, the labeling of individual convective echoes was also implemented by giving a certain size and intensity as conditions. Finding and tracking convective echoes in real-time with high spatio-temporal resolution radar images will help detect signals early that can generate severe weather and respond preemptively to hazardous weather.

Acknowledgements:

This research was supportedby the "Development of analysis technologies for local-scale weather radar network and next generation radar (KMA2021-03221)" of "Development of integrated application technology for Korea weather radar" project funded by the Weather Radar Center, Korea Meteorological Administration.

How to cite: Mo, S.-J., Park, J., Gu, J.-Y., and Lee, S.: Convective objects detection using computer vision based on radar images, 11th European Conference on Severe Storms, Bucharest, Romania, 8–12 May 2023, ECSS2023-36, https://doi.org/10.5194/ecss2023-36, 2023.

A next-generation long wavelength adaptable/targetable research radar network, comprising an array of truck-borne quickly-deployable scanning 10-cm radars, S-band On Wheels (SOW), incorporating a Bistatic Adaptable Radar Network (BARN), can provide fine-scale S-band dual-polarization observations of the atmospheric boundary layer, convective, and other precipitating systems while simultaneously measuring dynamically meaningful fine-scale vector wind fields. 

SOW is a new paradigm for long-wavelength research radars, replacing large cumbersome expensive singular radars with a network of several smaller, nimbler, less expensive systems. 

SOW and BARN  will fill critical gaps in current observing systems, providing broadly and inexpensively available long wavelength, dual-polarimetric, near-ground, fine-scale, vector wind observations.   

• When implemented, a network of 4 SOWs, SOWNET, will replace single 10-cm large 10-cm 1° radars with an array of smaller, 5.5 m (18’) antenna, quickly-deployable, 1.5° beamwidth truck-borne radars. 
• With multiple SOWs, typical ranges to targets are much shorter, resulting in improved resolution compared to single 1° 10-cm radars. 

• 1,2,3, or 4 SOWs can comprise a SOWNET deployment, customizing for small or large missions.   Inexpensive deployments of 1-2 SOWs qualitatively broaden access to this critical observational capability

• BARN enables multiple-Doppler vector wind measurements over targeted regions.
• SOWNET provides  moderate-resolution multiple-Doppler measurements, BARN provides  finer-scale over smaller domains. 
• BARN units are coupled with single or multiple SOWS, COW, or DOWs.  
• Stationary BARN units are unattended, low power, and similar to deployable weather stations
• Highly redundant BARN units provide extreme reliability of multiple-Doppler operation.

How to cite: Wurman, J. and Kosiba, K.: Mobile S-band and Bistatic Networks for Severe Storms, 11th European Conference on Severe Storms, Bucharest, Romania, 8–12 May 2023, ECSS2023-110, https://doi.org/10.5194/ecss2023-110, 2023.

The PERiLS (Propagation, Evolution and Rotation in Linear Storms) project is designed to study tornadoes produced by Quasi-Linear Convective Systems (QLCS) in the southeast United States.  QLCS-spawned tornadoes pose a significant threat to lives and property, but forecasting QLCS tornado events poses special challenges, more so than forecasting supercell tornadoes.  PERiLS is the largest and most ambitious field project focusing on QLCSs tornadoes, combining a dense, adaptable X- and C-band research radar array, including substantial instrumentation from the Flexible Array of Radars and Mesonets (FARM) including  the new quickly-assembled C-band On Wheels (COW), two Doppler On Wheels (DOW) a multitude of quickly-deployable surface instruments (PODNET), the UI deployable wind profiler, Mobile Mesonets, and several upper air sounding systems, to provide the sampling necessary to address environmental factors and storm processes that lead to QLCS tornadogenesis.  PERiLS is a multi-year field project; the first field phase occurred from 1 March to 1 May 2022; and the second field phase from 8 February to 8 May 2023.  

Preliminary data and analyses that address the science objectives of the National Science Foundation research teams, the pre-scouting and design of a radar network for each IOP, and other unique experimental field project design will be discussed.  During the 2022 field phase, PERiLS conducted four IOPs, during which tornado strength rotations were observed.  Preliminary analyses of IOPs 1 and 3 will be presented and an overview of the data collected during PERILS-2023 will be presented. 

How to cite: Kosiba, K., Wurman, J., Trapp, J., Nesbitt, S., and Parker, M.: Overview of the PERiLS (Propagation, Evolution and Rotation in Linear Storms) Project, 11th European Conference on Severe Storms, Bucharest, Romania, 8–12 May 2023, ECSS2023-112, https://doi.org/10.5194/ecss2023-112, 2023.

In order to characterize the hurricane boundary layer structures over a range of hurricane intensities, the Doppler on Wheels radars (DOWs) deployed in several hurricanes during the 2020 season, obtaining both dual-Doppler and rapid single-Doppler observations in the boundary layer of landfalling hurricanes. Results will be presented from three hurricanes:  Hurricane Laura, Hurricane Sally, and Hurricane Delta. These results will be discussed in the context of standard hurricane wind models.

Two DOWs targeted landfalling Category 4 Hurricane Laura. The DOWs deployed in southwestern Louisiana during landfall.  As is usual, the DOW radars operated in the most intense wind regions of the hurricane, collecting fine-scale, near-surface data in the eyewall near landfall.  The dual-DOW baseline was a very short ~6.3 km, providing ~60 m spatial resolution in the center of the dual-Doppler lobes. Anemometer data at 1 Hz were collected from DOW masts ~8-10 m above radar level (ARL). Laura is the 1st ever fine-scale dual-Doppler deployment sampling the HBL and eyewall in a Category 4 hurricane at landfall.   

Single-Doppler radar data were collected in Hurricanes Sally and Delta.  This allowed for the two-dimensional quantification rapidly evolving of boundary layer structures.  An array of surface based instruments, including a prototype, “POLENET”, which attaches existing infrastructure, allowing for a customizable observation level, were deployed in Hurricane Delta in order to correlate observations at radar level with surface observations.  Using corrections based on turbulence statistics and roughness lengths, a reduction factor was derived for the radar winds, allowing  for comparison between radar level winds and winds observed at 1, 2, and 10 m.  

The HBL is comprised of coherent structures that are potentially responsible for significant transport of turbulent fluxes throughout the HBL as well as regions of enhanced damage at the surface.  These coherent structures are not well understood and consequently their effects are poorly represented in numerical models.  In order to characterize the HBL structures over a range of hurricane intensities, DOWs deployed in several hurricanes during the 2020 season, obtaining both dual-Doppler and rapid single-Doppler observations in the boundary layer of landfalling hurricanes.

How to cite: Kosiba, K. and Wurman, J.: Fine-Scale Hurricane Boundary Layer Structure, 11th European Conference on Severe Storms, Bucharest, Romania, 8–12 May 2023, ECSS2023-113, https://doi.org/10.5194/ecss2023-113, 2023.

The Flexible Array of Radars and Mesonets (FARM) Facility is an extensive mobile/quickly-deployable (MQD) multiple-Doppler radar and in-situ instrumentation network hosted by the University of Illinois, with a design focus on obtaining targeted observations in Severe Local Storms. 

The FARM comprises four mobile / quickly-deployable radars: two X-band dual-polarization, dual-frequency (DPDF) , Doppler On Wheels DOW6/DOW7, the Rapid-Scan DOW (RSDOW), and a quickly-deployable (QD) DPDF C-band On Wheels (COW).

The FARM also includes 3 mobile mesonet (MM) vehicles with 3.5-m masts, an array of rugged  QD weather stations (PODNET), QD weather stations deployed on infrastructure such as light/power poles (POLENET), four disdrometers, six MQD upper air sounding systems and a Mobile Operations and Repair Center (MORC).

The FARM’s integration of radar, in situ, and sounding systems provides robust kinematic, thermodynamic, and microphysical observations.  Components of FARM (previously called the DOW Facility)  have deployed to >30 projects during 1995-2022 in North and South America and Europe (including COPS and MAP), obtaining pioneering observations of a myriad of small spatial scale and short temporal scale phenomena including tornadoes, hurricanes, lake-effect snow storms, aircraft-affecting turbulence, convection initiation, microbursts, intense precipitation systems, boundary layer structures and evolution, airborne hazardous substances, coastal storms, wildfires and wildfire suppression efforts, weather modification effects, and mountain/alpine winds and precipitation.

This poster will focus on the design, capabilities, and most recent updates to the FARM Facility, including very recent and anticipated future missions, including LEE (2022-2023), PERILS-2022 and 2023, ICE-CHIP (2024-2025), CROCUS (2024-2026), Tornado Structure Study (2023-2024), CREST 2025.  

Proposed major upgrades to the FARM targeted observing network, including the S-Band On Wheels NETWORK (SOW-NET) replacing large stationary S-band research radars, and the Bistatic Adaptable Radar Network (BARN) will be summarized.

How to cite: Wurman, J., Kosiba, K., Trapp, J., and Nesbitt, S.: The Flexible Array of Radars and Mesonets (FARM), 11th European Conference on Severe Storms, Bucharest, Romania, 8–12 May 2023, ECSS2023-114, https://doi.org/10.5194/ecss2023-114, 2023.

On 24^th June 2021 a devastating F4 tornado occurred in southern Moravia (SE of Czechia) that directly caused 6 fatalities and about 200 injuries. Approximately 200 houses and buildings out of about 1200 damaged ones had to be torn down. It has been the most severe tornado in modern history of Czechia.

Besides other data sources, the event was captured by C-band polarimetric Doppler radars of the Czech Weather Radar Network (CZRAD) as well by the LINET lightning detection network. Contribution will present analysis of these data and discuss their utilization in operational severe storm nowcasting in the Czech Hydrometeorological Institute. Operational nowcasting algorithm CELLTRACK for convective storm nowcasting and web-based application JSMeteoView2 for radar and lightning data analysis and display will be introduced.

The pronounced Doppler radar signatures of supercell storms like the hook echo, bounded weak echo region and the mesocyclone signature will be shown together with signatures derived from the polarimetric radar moments such as RHO_HV ring, ZDR arc/ring or K_DP column.

Contribution will also present comparison of various radar and lightning characteristics of tornadic storm with characteristics of all other storms identified over Czech Weather Radar Network domain by the CELLTRACK nowcasting algorithm during the investigated period of 24^th June 2021.

How to cite: Novak, P. and Kyznarová, H.: Analysis of Tornadic Storm in Southern Moravia on 24th June 2021 Based on Polarimetric Doppler Weather Radar and Lightning Detection Data, 11th European Conference on Severe Storms, Bucharest, Romania, 8–12 May 2023, ECSS2023-116, https://doi.org/10.5194/ecss2023-116, 2023.

Bulgaria is a country with a high frequency of thunderstorms during the warm season. Extreme convection, leading to torrential rain and large hail, and more specifically a supercell development was discussed in this case study. Radar data from S-band Doppler radars were used for the analysis. The full volume scan had a maximum range of 300 km and was completed in 4 minutes. All radar products shown throughout the study were generated by the Interactive Radar Information System (IRIS) Analysis of Vaisala.

On the 29-th of May 2022 over the territory of Bulgaria there was a 500-hpa trough with the center of the upper level low over the Scandinavian Peninsula. On the surface pressure chart there was a sequence of cold fronts. The upper level flow and the one near the ground had opposite directions – northern and predominantly southern respectively. This leads to strengthening of the vertical wind shear. This synoptic setup was favorable for severe convection development. Data for temperature stratification of the atmosphere, instability indices, wind hodograph, etc. were additionally used.

In the afternoon an isolated convective cell was registered in Southern Bulgaria, which had maximum radar reflectivity Zmax=23 dBZ at height of 6.8 km (-23°C) at 15:47 EET. The cell grew rapidly and after 20 minutes Zmax was 60 dBZ and the storm acquired characteristics of a supercell. A mesocyclonic vortex was visible on the Doppler radar. The cell acquired a V-shaped structure, and later on it split into two cells, both of which retained high radar reflectivity. The cells passed over the Stara planina mountain and the left-moving cell kept high values of radar characteristics for a long time. The right-moving cell also maintained high values of radar reflectivity, but had shorter life time and its intensity was lower.  Both cells produced multiple convective hazards along their paths. The hazards associated with the left-moving cell were severe hail (hailstone sizes greater than 2 cm in diameter), strong wind gusts, heavy rain and intense lighting activity.

Based on the radar data the presence of the typical supercellular radar signatures, such as weak echo region (WER), bounded weak echo region (BWER), hook echo, V-notch and TBSS are presented. The storm severity and the presence of large hail stones were confirmed by maximum radar reflectivity, VIL (Vertical integrated liquid) and VILD (VIL density).

How to cite: Barakova, D., Dimitrova, T., Georgiev, S., and Kadiyska, N.: Analysis of splitting supercell storm based on the Doppler weather radar data, 11th European Conference on Severe Storms, Bucharest, Romania, 8–12 May 2023, ECSS2023-123, https://doi.org/10.5194/ecss2023-123, 2023.

A mesoscale convective system (MCS) producing a derecho impacted four European countries 16-17 October 2022. The MCS produced high wind gusts and wind damage that started over Denmark, continued over Sweden, Estonia and Finland, along 1300 km long path. The MCS formed a large-scale bow echo that travelled through dense observation network over southern coastal waters of Finland resulting in detailed measurements of storm passage over surface observation stations, an observation mast and three radars. In Finland the maximum gust observed was 39,2 m/s, and storm-scale (≥25 m/s) wind gusts were observed on 16 surface observation stations. Wind measurements showed that the duration of storm-scale wind gusts were approximately 18 minutes and the maximum wind gusts (above 30 m/s) lasted approximately 10 minutes as the bow echo moved over observation stations. This unique observation data gives us insight to wind speeds and their duration in a derecho. The focus of this study is on comparison of radar observations of the MCS to the measurements from the surface observation network such as maximum wind gusts, temperature and cold pool strength, and change in the surface pressure. The synoptic and mesoscale environment is also described. The unusual seasonal time of the event caused extra challenge in its forecasting.

How to cite: Rauhala, J.: A derecho in northern Europe, 11th European Conference on Severe Storms, Bucharest, Romania, 8–12 May 2023, ECSS2023-149, https://doi.org/10.5194/ecss2023-149, 2023.