By the end of the loop, you'll see a long, continuous squall line stretching from western Ohio to Tennessee. 2217 Earth and Engineering Sciences Building, University Park, Pennsylvania 16802 Later, further numerical investigations provided by Miglietta et al.
The elevation angle was set at 0.3°. While squall lines can produce any kind of severe weather, they most prominently produce damaging straight-line winds. Hence, combined with the standard reflectivity, ZDR may help discriminate between oblate particles (e.g. These results confirm the key role of an adequate regional radar coverage in supporting daily operations of forecasting centres. Derechos are most common from May through July in the United States, and most areas of the eastern U.S. (east of the Rockies) experience a derecho at least once every few years, on average. Although occurring in two different periods of the year, the first two case studies, i.e.
Squall lines are common across the United States east of the Rockies, especially during the spring when the atmosphere is most "dynamic." As explained in the next section, smaller‐scale but far more intense bow echoes occurred on 10 October 2015 when damaging straight‐line winds locally greater than 100 km h−1 were recorded, especially across the central part of Salento Peninsula. In general, although several mechanisms leading to the formation of a squall line include those typical of strong isolated thunderstorms, specific environmental conditions are needed to produce and sustain the convection in squall line thunderstorms. However, a misalignment between Z and ZDR maxima is certainly more remarkable in this case than for the previous one. Pictures taken by local spotters in (a) Santeramo in Colle (in the province of Bari, central part of the Apulia region) and (b) Lecce, showing hail piled up after the passage of the squall line.
Range height indicator views provided by the Torchiarolo radar display many similarities with regard to inner structure and microphysical properties of the two squall lines. As a consequence, horizontal pulses crossing this area suffered from strong attenuation, thus producing the typical ZDR shadow downrange of the core. Mesoscale convective systems (MCSs) are generally defined as an ensemble of convective storms with a lifecycle greater than that of the single elements. Low values of the correlation co‐efficient can indeed be observed for meteorological echoes characterized by high variability in shape, size, orientation and phase. Furthermore, it is clear from this study that, in this scenario, high resolution polarimetric Doppler data provided by the Torchiarolo radar and, in the near future, by a second Doppler radar in Mesagne may significantly help researchers and forecasters in understanding and promptly detecting severe weather episodes, thus guaranteeing an adequate nowcasting capability over the whole region. Finally, area 1 is a thin horizontal strip embedded within the stratiform precipitation region of the squall line. 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 continuously variable pulse width range is 0.15–2.0 µs at a pulse repetition frequency up to 5 kHz, while the peak transmitting power is as high as 250 kW. The line, under the influence of a strong rear inflow jet descending from mid‐levels to the surface, started bowing out in less than 10 min, hence displaying a clear bow echo signature by 0946 UTC. At about 0920 UTC, on the northern part of the Ionian coast, embedded in a stratified structure, isolated convective cells quickly organized into a small‐scale squall line extending north–south for almost 30 km (Figure 12).
It roughly corresponds to the boundary of the low reflectivity area preceding the core of the system along the leading edge. Range rings are at 50 km intervals, while the elevation angle was set at 0.3°. While the differential reflectivity helps determine the dominant target orientation as well as the microphysical properties of atmospheric particles such as size, shape and phase composition, the correlation co‐efficient ρ represents a measure of similarity between horizontal and vertical power and the phase of each pulse in a given volume.
Consequently, a typical ZDR ‘shadow’ extends throughout area 4, exactly in the downrange portion of the radar echo: negative ZDR values as low as −20 dB about 35 km from the radar can be observed in Figure 5(b). The cut‐off quickly travelled from central Italy toward the southern Adriatic region flowing over a warmer and relatively humid layer at low levels. The 1150Z radar mosaic from May 2, 2008 shows a prominent bow echo along a squall line. Not only tornadoes but also unusual Mediterranean tropical‐like cyclones traversing Salento Peninsula can be found in the literature. As in the previous case, the electromagnetic wave propagating downrange of the core through area 3 suffered from a consistent attenuation of its horizontal component, thus leading to a dramatic drop of the differential reflectivity well below −6 dB.
In Section 2 the technical features of the newly installed Torchiarolo radar are briefly illustrated with an overview of the microphysical interpretation of its polarimetric variables. But, there's another kind of derecho that's more common during the warm season. Therefore, with the squall line approaching the radar location from the west, the operational range was progressively shortened from 250 to 50 km. Tornadoes are one major element of severe weather. The elevation angle was set at 0.3°.
Squall lines can also be broken (cell-sized gaps between thunderstorms).
Specifically, owing to smaller raindrops being lifted by the updraft to higher and colder altitudes, a ZDR column appears as a narrow vertical region with positive values of differential reflectivity extending above the freezing level (Kumjian et al., 2014).
The convection in a squall line tends to be relatively narrow, while the characteristic length can range from approximately 50 miles to hundreds of miles. As for the general structure of a mature squall line, three main linear MCS categories proposed by Parker and Johnson (2000) are adopted for the discussion of the case studies in this study.
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. The horizontal and the vertical scale of the SC case was the largest, too. To the best of the authors' knowledge, this is the first study giving detailed information about the kinematic and microphysical properties of a linear mesoscale convective system crossing Salento Peninsula, and hence it complements the current state of the art of severe weather phenomena affecting this area.