One of the purposes of this initial study has been to accurately simulate the evolution and structure of flanking lines using a numerical cloud model. In addition, the processes which support the structure were explored. The nested grid COMMAS cloud model was initialized with single perturbation in an otherwise homogeneous supercell environment. The control simulation was integrated for over four hours. The flanking line begins to form about 45 minutes into the simulation at a time that coincides with the rain water and its accompanying cold pool reaching the surface. The line then develops outward from the main updraft, as the rear flank gust front forms at the leading edge of the cold pool. The flanking line moves at approximately the same speed as its parent supercell with only minor changes in orientation throughout the simulation.

The flanking line quickly develops a "stair-stepped" appearance which is commonly observed (Bluestein, 1986). This "stair-stepped" appearance can be explained by two factors: 1) near the main cell, the cold pool is deeper, and the gust front has a stepper leading edge; and 2) the orientation of the gust front near the main cell is more favorable for upright updrafts given there is a better balance between the environmental shear and the cold pool as discussed by Rotunno et al. (1988).

A number of questions remain after this initial study. Shallow to moderately deep flanking line updrafts were not distinct, most likely due to the fine grid 600 m resolution used although other factors may be involved since a 200 m resolution simulation did not produce distinct cell updrafts either. Further, the wind fields within the flanking line did not support movement of the line convection toward the main supercell updraft. Therefore, the mechanism by which flanking line cells can merge with the main supercell updraft as sometimes observed remains unclear and requires continued study. In addition, a number of soundings were initially explored; however, many of them did not produce a flanking line. The reasons for this will be studied in light of the fact that many supercells are associated observationally with flanking lines. Further, analysis of existing simulations will explore the low-level vorticities that continually developed near the main supercell updraft and then move down the flanking line away from this updraft and the differences in overall storm structure due to the presense of inversions and/or shallow moist layers.