Satellite and Mesometeorology Research Paper 156. Because of a strong jet stream at the base of the trough, the cold 500 hPa tongue assumed a slight negative tilt across the central part of the Mediterranean Sea.
Indeed, in this way, by concentrating the same transmitting power in a shorter range, the relatively weak echo signals reflected back to the Torchiarolo radar would be better detected and recognized. Once formed, the squall line was progressively strengthened by the release of a moist layer of maritime air which, as a result of the lifting mechanism triggered by a cold front approaching from the west, continuously flowed into it driven at the ground by stiff south winds. the winter squall line and one occurring at the beginning of the fall season, both developed along an approaching cold front overlapping a pre‐existing warmer and more humid layer at the ground. The squall line observational study and related hydrometeor characterization was principally carried out by using polarimetric Doppler radar products provided by the Torchiarolo radar, in the southern Apulia region (Figure 1). The transmitted signal at 5.625 GHz is generated by a power MOSFET modulator magnetron transmitter supplied by Applied Systems Engineering. (2005), the geological and geomorphological configuration of Salento emphasizes the impact of flooding episodes leading to high economic damage. Part I: Theoretical simulations using spectral microphysical modeling, Depolarization in ice crystals and its effect on radar polarimetric measurements, Dual‐polarization observations of microbursts associated with intense convection: the 20 July storm during the MIST Project, The genesis of severe, long‐lived bow echoes. The presence of melting resonant‐sized hailstones mixed with large raindrops can also be recognized in area 3, where a consistent drop of the correlation co‐efficient (as low as 0.85) together with a considerable increase of the differential reflectivity can be observed. However, it cannot be ruled out that the system, in its mature stage, maintained its original trailing stratiform organization mode, thus simply merging with a pre‐existing stratiform region over the Strait of Otranto associated with the warm branch of the cyclonic circulation. Have you ever seen the movie, The Wizard of Oz? As depicted in Figure 4, the line of thunderstorms, extending for about 120 km, started affecting the central part of Apulia at about 2000 UTC, while it left the eastern coast of Salento within 3 h. On its way moving toward the east, the observed squall line system clearly weakened over Salento mainland assuming a wider and more disorganized shape; in contrast, it rapidly regained vigour over the more unstable and warmer environment of the Adriatic Sea. Low values of the correlation co‐efficient can indeed be observed for meteorological echoes characterized by high variability in shape, size, orientation and phase.
A prime example of a progressive derecho occurred on June 29, 2012, which started as a cluster of thunderstorms over northwest Illinois and east-central Indiana. In addition to formally defining each of these, you should be able to describe their basic structure and impacts. Not only tornadoes but also unusual Mediterranean tropical‐like cyclones traversing Salento Peninsula can be found in the literature. [Colour figure can be viewed at, Sea level pressure charts (in hPa, solid lines every 4 hPa) on (a) 22 January 2015 at 1800 UTC and (b) 23 January 2015 at 0000 UTC. Furthermore, a cross‐coupling between the vertical and horizontal components of the transmitted wave can be observed in the higher parts of the convective storm. The three main subsystems of the Torchiarolo radar are shown in bold. The waterspout activity, as reported by local spotters, occurred on the southwestern side of the squall line where, despite any evident radar echo being recorded, a further vortex with anticyclonic circulation might form and develop. Complex data, converted into moments and products, are sent to the Configurable Interactive Data Display (CIDD) software for local analysis and visualization. It had sections that bulged forward. Over time, progressive derechos develop multiple bow echoes and end up resembling squall lines as they mature. In order to investigate kinematic and microphysical properties of the observed convective systems, radar imagery from the C‐band dual polarity Doppler radar recently installed in Torchiarolo, in the central part of Salento Peninsula, has been presented and analysed. (1986), this abrupt change in ZDR, occurring in correspondence with the external zero level, clearly shows the microphysical changes of the hailstone surface from dry to wet as well as the smoothing of dry growth lobes, the penetration of liquid water in the interior of the internal porous stone, and finally the shedding of large drops from the equatorial plane of the stone itself (Figure 5(a)). Polarimetric radar variables at 2047 UTC 22 January 2015 showing the observed squall line while crossing the Salento Peninsula: (a) reflectivity (dBZ), (b) differential reflectivity (dB) and (c) correlation co‐efficient shown on a range height indicator view taken along the 255.6° azimuth angle and subdivided into four main areas (dashed lines). The rest of the paper is organized in three sections.
Squall lines tend to develop along (or very near) surface boundaries like cold fronts or surface troughs of low pressure because these boundaries mark zones of low-level convergence. Hence, combined with the standard reflectivity, ZDR may help discriminate between oblate particles (e.g. A bow echo is crescent-shaped radar echo that sometimes appears along the otherwise linear reflectivity pattern associated with a squall line, which is frequently associated with damaging straight-line winds and occasionally, brief tornadoes. Derecho is actually a Spanish word that, in this context, translates to "straight-ahead" or "direct." A warm weather phenomenon, derechos occur mostly in summer, betw… To this end, range height indicator (RHI) plots along the 255.6° azimuth are reported in Figure 5. This squall line formed in conjunction with strong low-level convergence along a cold front (18Z surface analysis), and caused hundreds of reports of damaging winds (each marked by a blue dot on the map of SPC storm reports for January 29, 2008). Therefore, with the squall line approaching the radar location from the west, the operational range was progressively shortened from 250 to 50 km. As in the previous case, a detailed microphysical analysis of the vertical profile can be performed by means of polarimetric variables provided by the Torchiarolo radar. Course Author: Steven Seman (Assistant Teaching Professor, Department of Meteorology and Atmospheric Science, College of Earth and Mineral Sciences, Mesoscale convective systems (MCSs) are generally defined as an ensemble of convective storms with a lifecycle greater than that of the single elements. Finally, area 1 is a thin horizontal strip embedded within the stratiform precipitation region of the squall line. By comparing this vertical profile with that of the previous example (Figure 5), some typical radar signatures associated with linear MCSs can easily be recognized. Up next, we'll shift our focus to tornadoes -- the wind-related threat that takes all the headlines. The reports must be sufficiently spread apart (at least 64 kliometers, or about 40 miles) to indicate that the thunderstorms maintained noteworthy intensity for a sufficiently long time. ZDR close to 0 dB associated with large values of the reflectivity field and a correlation co‐efficient near 1 are a typical radar signature of dry, chaotically falling hailstones brought below the melting level by intense downdrafts. The advection of a cold front over an unstable air mass, the presence of a middle‐level dryline proceeding ahead of a low‐level moist layer, topographic features, the outflow coming from areas of prior convection, moderate deep layer shear and strong low‐level shear are only some of the most important synoptic settings playing a significant role in squall line initiation and maintenance (Hane, 1986). Working off-campus? On radar reflectivity, a bow echo appears in this region.
Additionally, for each squall line episode, significant radar echoes suggesting potential severe convective weather, such as heavy rain, hail and damaging wind gusts, are also recognized and investigated. Hailstones started melting at about 0.5 km height as illustrated by a sharp enhancement of differential reflectivity together with a decrease in ρ just above the ground. The Torchiarolo plan position indicator maps at 0.3° elevation angle at 1027 UTC on 24 September 2015: (a) reflectivity (dBZ) and (b) Doppler radial velocity (m s, Weather chart analysis on 10 October 2015 at 1200 UTC showing sea level pressure (in hPa, solid lines every 4 hPa) with the position of the fronts around the surface low, indicated by the letter L: warm front (solid line with circles), cold front (solid line with triangles) and the occlusion (solid line with alternating triangles and circles). The microphysical characteristics of the squall line are noticeably different among these three stages. Learn more. Therefore, the present study clearly confirms the key role of the new advanced weather radar installed in Torchiarolo which thus represents a powerful tool giving researchers and forecasters valuable information about kinematic and microphysical properties of severe weather systems crossing Apulia region, especially Salento Peninsula. More details may be inferred from the pre‐system wind profile illustrated in the hodograph plot in Figure 3, where the magnitude and direction of the wind shear vector over two different layers (0–3 and 0–6 km) are reported and described. When I wrote the title to this section, I couldn't help but think of that scene. But, straight-line winds aren't the only wind-related threat associated with thunderstorms. Small size hailstones (locally mixed with graupel) were recorded in several places along the observed squall line, as shown by two pictures taken by local spotters in Santeramo in Colle and Lecce and reported in Figure 6.
Specifically, three relevant events that occurred in January, at the end of September and in October are described, combining thermodynamic and synoptic analysis with radar imagery delivered by the cutting‐edge polarimetric Doppler radar recently installed in Torchiarolo, in the central part of Salento Peninsula. The thunderstorms that we studied previously (single cells, multicells, and supercells) were all relatively discrete (meaning relatively isolated). (2013) demonstrate that, with respect to dry hail, small melting hailstones are characterized by particularly large values of ZDR comparable with those of big raindrops. Derechos are most common in a swath from the southern Plains to the southern Great Lakes region. As for the observed squall line, the shear environment exhibits low to moderate values of low‐level wind shear (below 3 km), while larger values up to about 20 m s−1 can be observed over the 0–6 km bulk layer.
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