Keynote Talk: BAMEX Observations of Mesoscale Convective Vortices

The study of MCVs spawned from organized convection constituted a major component of BAMEX. In all, five mature MCVs were sampled with dropsondes. In this talk we first review the convection that gave rise to these MCVs and the attendant synoptic-scale conditions. We then present analysis of the kinematic and thermodynamic structure of each MCV, including an assessment of the degree of dynamical balance. Vertical motion within the circulation of each vortex is computed and used to interpret thermodynamic variations that promote new convection downshear. Horizontal advection of temperature induced by the MCV was significant in some cases, leading to the structures resembling extratropical cyclones, but with length scales of only a few hundred kilometers.

Vortices spanning a considerable range of size, intensity and structure were observed. The longest-lived case, 11 June 2003, was part of a multi-day vortex that transitioned from elevated circulation to a deep cyclone extending through the troposphere. Although the MCVs formed in vertical wind shears of varying strengths, only the 11 June case occurred in shear that was less than 5 m/s over the depth of the vortex. In two of the cases, the mesoscale kinematic and thermodynamic modification due to the MCV promoted severe weather in an environment that would be otherwise considered benign.