Start
April 23, 2021 - 3:00 pm
End
April 23, 2021 - 4:00 pm
Categories
Convective Meteorology (Mesoscale Dynamics)Convective Meteorology (Mesoscale Dynamics) Seminar
Storm-Scale Evolution Leading to Cyclic Tornadogenesis in a 50-m, Idealized Numerical Simulation of a Supercell
Mauricio I. Oliveira
Friday, April 23rd
3:00pm
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https://meet.google.com/ksh-txvg-kni
Supercells thunderstorms are the most prolific tornado producers among all modes of severe convection. In many situations, especially during tornado outbreak days, supercells tend to produce tornadoes cyclically, which may include a mixture of short-lived tornadoes and strong, long-track tornadoes. Conceptual models of cyclic tornadogenesis include, in short, (i) the development of a midlevel mesocyclone, (ii) the formation of a rear-flank downdraft and a low-level mesocyclone, (iii) intensification of the low-level mesocyclone and tornadogenesis, (iv) tornado maturation, and (v) decay of the initial tornado(es) followed by (or concomitant with) formation of a new updraft and mesocyclone/tornado near the rear-flank gust front.
In this study, a high-resolution (50-m), idealized, horizontally homogeneous numerical simulation of a supercell is used to explore the finescale evolution of cyclic tornadogenesis. In this setup, the evolution of the cyclic supercell, including the frequency of tornado formation and differences among them can be readily attributed to complex inner storm-scale variations. During the 4.5 h of model integration, four tornadoes develop. Tornado formation is preceded by a significant intensification of low-level updrafts with an associated pressure drop aloft and north-northeast of the tornadoes. The low-pressure lobe northeast of the low-level mesocyclone precedes tornadogenesis and is related to acceleration of the storm-relative inflow into the low-level updraft, similar to previous observations of cyclic supercells. The life cycle of the first tornado (30 min) occurs when the parent supercell displays a “classic” morphology; subsequent tornadoes develop as the supercell transitions into a high-precipitation mode, causing rapid occlusion and decay of the tornadoes (average lifetime = 17.4 min). A preliminary assessment of the storm-scale processes affecting tornado cycling in comparison with previous conceptual models will be presented.