On 18 June 1997 two simultaneous supercells 50 km apart swept the Po valley W-NW to E-SE. An exceptional hailfall lasted for more than 3 hours over a strip 200km wide. There are no records of companion supercells over northern Italy, a fact that attributes to the present observations a considerable meteorological interest. The forcing due to a baroclinic wave disturbance created the synoptic conditions favourable for storm development. A closer mesoscale analysis conducted using the Local Analysis and Prediction System (LAPS) indicates that the interaction of the storm systems with the low-level frontal high-humidity band is a key aspect of their evolution. The operational polarimetric Doppler weather radar of S. Pietro Capo®ume was used for a volumetric analysis of the storm system focusing on the microphysical and dynamical structure, and wind patterns. Re¯ectivity and Doppler wind ®elds document the transition from multicell to supercell phase for one of the storms. Differential re¯ectivity (ZDR) ®elds are examined. Positive ZDR columns are detected in connection with the storms strong updraft. Flare echoes hint to the presence of substantial hailshafts. The spectrum width ®eld is used to investigate internal motions. Limited dual Doppler analysis is carried out and results are discussed in terms of storm evolution properties.
The 18 June 1997 Companion supercells: Multiparametric Doppler radar analysis
V Levizzani;
2000
Abstract
On 18 June 1997 two simultaneous supercells 50 km apart swept the Po valley W-NW to E-SE. An exceptional hailfall lasted for more than 3 hours over a strip 200km wide. There are no records of companion supercells over northern Italy, a fact that attributes to the present observations a considerable meteorological interest. The forcing due to a baroclinic wave disturbance created the synoptic conditions favourable for storm development. A closer mesoscale analysis conducted using the Local Analysis and Prediction System (LAPS) indicates that the interaction of the storm systems with the low-level frontal high-humidity band is a key aspect of their evolution. The operational polarimetric Doppler weather radar of S. Pietro Capo®ume was used for a volumetric analysis of the storm system focusing on the microphysical and dynamical structure, and wind patterns. Re¯ectivity and Doppler wind ®elds document the transition from multicell to supercell phase for one of the storms. Differential re¯ectivity (ZDR) ®elds are examined. Positive ZDR columns are detected in connection with the storms strong updraft. Flare echoes hint to the presence of substantial hailshafts. The spectrum width ®eld is used to investigate internal motions. Limited dual Doppler analysis is carried out and results are discussed in terms of storm evolution properties.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
