Summary – modeling research tells us that cells merge into a line when the shear is perpendicular to the boundary…

• Isolated cells over south central NY in this case appeared to merge into a line over northeast Pa as the shear vector turned from around 260 to 280 degrees.

• Question: What was the orientation of the boundary? What boundary should we use (large-scale or smaller scale).

• If one uses the axis of pressure falls as the boundary, then you could argue that the shear became more perpendicular to the boundary as the cells merged.