Via Vetoio
L'Aquila
Mario Marcello MiglietMario (CNR-ISAC, Padua, Italy): “Conceptual models for tornadoes in Italy”
Abstract: Although rare, severe tornadoes may occasionally strike Italy, sometimes causing severe damage and even fatalities. The strongest tornadoes typically occur in the early afternoon, during late spring-early summer in the northern regions and during autumn in southern Italy and Sicily. This seasonal distribution reflects the diverse nature of tornadoes, which generally originate inland in the former case, offshore in the latter. Some areas with greater frequency of occurrence have been identified in the Venetian plain and the Po valley, the extreme southern tip of Apulia, the Tyrrhenian and Ligurian coasts, Sicily. Numerical simulations in specific case studies and reanalysis data revealed that the conditions favorable to tornado-spawning supercells in Italy change with the subregions considered:
- In the Ionian regions, supercells are triggered by the arrival of air with strong low-level wind shear and moderate humidity content;
- In the Po valley, tornadogenesis is favored by the advection of cool air above very hot and moist air affecting the low levels in the typical season of occurrence (summer); also, a dry line generated by downslope winds from the Apennines controls the position of the warm tongue from the Adriatic Sea, thus the area where tornadogenesis occurs;
- In the Tyrrhenian regions, one mechanism of tornadogenesis was identified, associated with linear convective systems triggered by low-level convergence.
Finally, some general indications about the possible effect of climate change on tornado frequency and intensity are provided.