Mesoscale convective vortices observed during BAMEX. Part II: Influences on convection initiation

This presentation examines convection initation subsequent to mesoscale convective vortex (MCV) formation in the context of the observed environmental and MCV structural characteristics reported in part I. Each of the five observed MCVs had regions of both lower-tropospheric mesoscale ascent and favorable temperature/moisture advections, however, the redevelopment of significant deep convection was limited to three of the five cases. For the cases in which deep convection redeveloped, the MCV-induced vertical motions and horizontal advections resulted in significant variation in thermodynamic stability across the circulation. and thus helped focus the location of convection initiation within the preexisting background region of near-surface frontal convergence. The lack of convective redevelopment in the other two cases is attributed to thermodynamically stable conditions in the path of the MCVs. The lower to midtropospheric vertical shear typically exhibited greatest enhancement (over background values) near the radius of maximum winds south and east of the vortex center. The maximum values of vertical shear (~ 20 m/s over the lowest 4 km) are similar to those commonly reported with severe weather outbreaks, however, the most intense convection within the MCV circulation tended to occur farther to the southeast, where thermodynamic instability was greatest.