Severe convective supercell outbreak over western Bulgaria on July 8, 2014 (original) (raw)
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Using the cell tracker TITAN (Thunderstorm Identification, Tracking, Analysis, and Nowcasting) and a manual synoptic classification scheme, individual storms are obtained and classified for the period 2006 to 2010 for Thessaly into seven distinct synoptic patterns. Following a strict storm-tracking procedure, 2875 single cell storms are identified during the months April to September for the five-year period. The aim of this study is to identify differences in formation, structure, intensity and behavior of the storms among the recognized storm producing synoptic patterns over the area. Storms are characterized through their initiation time, duration, speed, direction, maximum top, maximum reflectivity, rain rate, volume, area and precipitation area. Results indicate that certain differences exist in storm characteristics among different synoptic patterns such as speed, direction, maximum top, maximum reflectivity and area. Storms following NW to SE movement are well organized exhibiting higher intensities and lifetime. Storms following SW to NE movement exhibit more complex structure, move faster, cover wider area and form in bigger numbers. In both cases orographic forced lifting is the dominant storm producing mechanism.
Noteworthy C-band radar parameters of storms on hail days in northwestern Spain
Atmospheric Research, 2001
The data provided by a meteorological C-band radar have been employed in order to analyze the behavior of 224 storms that occurred on hail days in the provinces of León and Zamora, in the northwest of Spain. A network of more than 700 voluntary observers supplied the necessary information to distinguish hailstorms from storms that did not produce hail precipitation. The observers also reported the size of the hailstones found.
Erad 2014-EIGHTH European Conference on Radar in Meteorology and Hydrology
2014
Supercell thunderstorms typically produce hail. The largest hail is commonly found at the edges of the updrafts, which allow sufficient growth time for hail to reach large sizes (Miller et al. 1988). An algorithm for hail recognition with the single polarization WSR-88D (Weather Surveillance Radar-Doppler) has been in use since early 1990s (Witt et al. 1994). Dual polarization radar capabilities allow measurements of differential reflectivity (ZDR), the correlation coefficient (ρhv), and differential phase (Φdp), which deliver additional information about scatterers. Studies by Balakrishnan and Zrnic (1990) of hail producing thunderstorms reveal low ZDR (about 0 dB) and reduced ρhv (as low as 0.8) in hail cores. These features are explained with tumbling non-spherical hailstones: the correlation coefficient drops because the scatterers are not spherical and ZDR is low because they tumble. Further works reveal variety of hail cases with reflectivities in a wide interval from ~ 30 to ...
Atmospheric Research, 2003
A brief overview of severe wind/hail storms over Bulgaria in the last 5 years (1997 -2001) is presented. Synoptic and thermodynamic analyses of 27 cases during 1999 -2001 (April -September) were performed. Among others, two events during this period produced extremely damaging winds. The first of them was associated with a tornado close to the Mediterranean coast on 15 May 1999 and has been already described in the literature. This paper illustrates the role of synoptic scale factors for generation of a second severe windstorm (that occurred near the Bulgarian capital Sofia on 22 May 2001) by using numerical model analysis fields. On the large scale, the circulation pattern was associated with a deformation middle-tropospheric field over the North Atlantic, Western Europe and Mediterranean. A zone of convergence in temperature and mass fields was formed over the Balkans, where there was an interleaving of warm, moist Mediterranean air advected in association with a warm front and cold dry air coming from the northwest in the eastern flank of an upper-level ridge. This synoptic circulation pattern produced deep convection along the boundary between the polar and subtropical high-level frontal systems. It is shown that synoptic-and meso-scale elements of the development may be revealed or confirmed by radiosounding data as well as by satellite and radar imagery. Data from the upper-air sounding of Sofia at 1200 UTC (available up to 650 hPa level) and other proximity soundings were processed and analysed. The obtained results show very high values of atmospheric instability indices (the energy of instability E i = 3785 J/kg, TT = 59 jC, Z (ULC) = 12.6 km). The updraft was up to 21.9 m/s and the difference of the wind velocity between 300-and 700-hPa levels was up to 12 m/s. Cloud water content reached up to 12.9 g/kg.
Study of 11 September 2004 hailstorm event using radar identification of 2-D systems and 3-D cells
Advances in Geosciences, 2006
The most important hail event recorded in the region of the Ebro Valley (NE Spain) in 2004 was the 11 September episode. Large hailstones (some of them with a diameter of over 30 mm) caused important damages in agriculture and properties. The hail event affected an area of 3848 ha and was caused by several multicellular systems. The aim of this paper is the analysis of the associated convective structures using the meteorological radar as well as the MM5 mesoscale model, thermodynamic data and a hailpad network. To achieve this end, the new hailstorm analysis tool RHAP (Rainfall events and Hailstorms Analysis Program) has been applied. It identifies tracks and characterises precipitation systems and convective cells, taking into account 2-D and 3-D structures. The event has also been studied with the TITAN software (Thunderstorm Identification, Tracking, Analysis and Nowcasting) in an attempt to compare both methods. Results show that the episode had a strong convective activity with CAPE values over 4000 J/kg and with hail-forming cells characterised by VIL (Vertical Integrated Liguid) exceeding 40 kg/m 2 , VILD (VIL density) over 4 g/m 3 , HP (Hail Probability) of 100% and SHP (Severe Hail Probability) of over 75%. The hail cells evolved into multicellular systems that lasted between 70 and 90 min. Finally, the comparison of RHAP and TITAN has shown significant correlations between methods.
Sounding-derived parameters associated with severe hail events in Romania
IDŐJÁRÁS Quarterly Journal of the Hungarian Meteorological Service , 2021
⎯ The present paper analyzes 549 severe weather events reported to the ESWD (European Severe Weather Database) that caused large hail in the territory of Romania. Values of atmospheric instability indices have been analyzed for these episodes using data from Bucharest and Budapest sounding stations. For a period of 140 days with episodes of large hail, 24 instability indices were analyzed to describe the atmospheric conditions of the main daily convective activity. The mean values for most indices characterize an unstable atmospheric environment. Of the indices that measure potential instability, VT (vertical totals index) and TT (totals index) had values that described a conductive atmospheric environment for the development of hailstorms. In addition, the interquartile values of LIV (lifted index using virtual temperature) had values lower than zero. For SWEAT (severe weather threat index) and CAPEV (convective available potential energy index using virtual temperature), only the values in the 75th percentile describe a very unstable environment (according to the literature). Strong linear correlations were registered between several pairs of indices such as CAPEV-LIV and SWEAT-SI that can be used for the operational forecast of hail.
Mesoscale and radar analysis of the 30 June 1998 supercell
On 30 June 1998 an intense squall line swept the central-eastern PO valley: large hail, damaging winds and a supercell were observed with these storms. The forcing due to a baroclinic wave disturbance created the synoptic conditions favourable for storm development. A mesoscale analysis, conducted using the Local Analysis and Prediction System (LAPS), shows the characteristic circulation in the wind field close to the ground from the western and the eastern borders of the PO valley, advecting humidity and increasing the wind shear. Moreover, analysis of temperature and humidity permits to follow movement of the system its across the valley. Reflectivity and Doppler wind fields observed by the C-band radar located at S. Pietro Capofiume, near Bologna, document the position and the intensity of precipitation and the strong rotational pattern associated with supercell. Dual polarisation permits to infer characteristics on the type of the hydrometeors.
Radar analysis of the life cycle of Mesoscale Convective Systems during the 10 June 2000 event
Natural Hazards and Earth System Sciences, 2005
The 10 June 2000 event was the largest flash flood event that occurred in the Northeast of Spain in the late 20th century, both as regards its meteorological features and its considerable social impact. This paper focuses on analysis of the structures that produced the heavy rainfalls, especially from the point of view of meteorological radar. Due to the fact that this case is a good example of a Mediterranean flash flood event, a final objective of this paper is to undertake a description of the evolution of the rainfall structure that would be sufficiently clear to be understood at an interdisciplinary forum. Then, it could be useful not only to improve conceptual meteorological models, but also for application in downscaling models. The main precipitation structure was a Mesoscale Convective System (MCS) that crossed the region and that developed as a consequence of the merging of two previous squall lines. The paper analyses the main meteorological features that led to the development and triggering of the heavy rainfalls, with special emphasis on the features of this MCS, its life cycle and its dynamic features. To this end, 2-D and 3-D algorithms were applied to the imagery recorded over the complete life cycle of the structures, which lasted approximately 18 h. Mesoscale and synoptic information were also considered. Results show that it was an NS-MCS, quasi-stationary during its stage of maturity as a consequence of the formation of a convective train, the different displacement directions of the 2-D structures and the 3-D structures, including the propagation of new cells, and the slow movement of the convergence line associated with the Mediterranean mesoscale low.
Radar Derived Storm Characteristics Over Central Greece
Individual storm measurements are obtained from the C-band weather radar, located close to the area of interest, using the cell tracker TITAN (thunderstorm identification, tracking, analysis, and nowcasting). The study aims in analyzing certain storm characteristics over central Greece, as a tool for investigating possible rain enhancement feasibility potential. The objective on this study is two folded: firstly, to analyze and describe storm characteristics and secondly, to identify differences in storm characteristics, structure and their behavior, among distinct synoptic situation patterns. The radar-based storm characteristics are extracted using certain thresholds. Storm characteristics include: storm initiation time, storm duration, storm motion, cloud top, reflectivity, storm volume and storm area. Frequency analyses of the aforementioned findings bring out evidences of the storm characteristics, their extends and limitations, providing thus an integrated view of the experienced isolated storms over the examined area. Moreover, the classification of the storm days reveals certain differences in several storm properties, indicating how isolated storms over central Greece vary under different synoptic situation patterns.