The Vertical vorticity structure within a squall line observed during BAMEX: Banded vorticity features and the evolution of a bowing segment

Conference: 
ICMCS-X
Presentation Type: 
Oral
Author(s): 
Abstract: 

A quasi-linear convective line with a trailing stratiform region developed during the Bow
Echo and Mesoscale Convective Vortex Experiment (BAMEX) while being sampled by
two airborne Doppler radars. The finescale reflectivity and Doppler velocities recorded
by the radars documented the evolution of the convective line. Bands of positive and
negative vertical vorticity oriented parallel to the convective line were resolved in the
analysis. This type of structure has rarely been reported in the literature and appears to
be a result of the tilting and subsequent stretching of ambient horizontal vorticity
produced by the low-level wind shear vector with a significant along-line component.
The radar analysis also documented the evolution of an embedded bow echo within the
convective line. Embedded bow echoes have been documented for a number of years,
however, a detailed analysis of its kinematic structure has not been previously reported in
the literature. The counterrotating circulations that are characteristic of bow echoes
appeared to be a result of tilting and stretching of the horizontal vorticity produced in the
cold pool. The analysis suggests that the location along the convective line where
embedded bow echoes form depend on the local depth of the cold pool. The rear-inflow
jet is largely driven by the combined effects of the counterrotating vortices and the
upshear-tilted updraft.