Structure and evolution of a convective band MCS

Abstract

The structure and evolution of the synoptic, mesoscale, and lightning characteristics of the 5 May 1993 non-squall line Mesoscale Convective System has been described. This storm was a long-lived Mesoscale Convective Complex. Its formation was influenced by strong low-level warm advection, weak vorticity advection, and weak vertical. wind shear. Its dissipation occurred as the storm encountered a more stable air mass which may have been influenced by storm induced subsidence. The cyclonic mesoscale circulation of the Mesoscale Convective Complex apparently aided in the formation of new lines of convection behind the primary convective line of the system. This process was repeated twice in the storm life cycle and led to multiple bands of convection. Indeed, this storm had three main lines: the leading line, the trailing one, and the small line near the center of the vortex. As the new lines formed, the vertical transport of momentum disrupted the symmetry of the mesovortex. However, as the line propagated eastward away from the vortex, the symmetric cyclonic circulation re-established itself. This Mesoscale Convective Complex produced flash rates in excess of 1000 h-I for twenty-four consecutive hours. The percentage of positive polarity flashes was higher during the formative and dissipating stages of the storm system. Positive flashes were also enhanced during mergers between convective bands. The flash locations during the mature stage of this storm suggest a bipolar pattern.