Yes, it has to do with upper level diffluence, however, that's not the entire story ... vertical wind shear plays a HUGE ROLE in getting that setup to occur ..
First, with directional wind shear (changing of wind directions with height, the air in the lower atmosphere begins to roll like a slow steamroller or a wave ... as updrafts begin to occur, it takes one of these horizontal columns, and turns it to a vertical position (but still tilted). As the updraft continues and provided the updraft is strong enough, the storm is born, and then grows, the rolling tube continues to spin and the supercell thunderstorm is born ... as the mid-level flow pushes into the vertical mesocyclone (the rolling tube), the flow of air is actually FORCED to go around the cell and splits north and south of the mesocyclone, creating the V-NOTCH configuration ... a sign of severe weather ... Sometimes you see what appears to be warmer cloud levels in a V-NOTCH configuration on satellite, when in actuality, the cloud top is SO HIGH, that it has entered the warmer troposphere ... although, the cloud top on IR will show warmer, the cloud top is actually higher than the V-NOTCH configuaration...
Also with supercells, you sometimes will see an overshooting top (a part of the cloud that actually punches through the equilibrium level - or where the anvil levels out - another indicator of a severe thunderstorm) ...
The May 7th, 1998 Edgefield Tornado - Visible towards Sunset ... notice the bumpy appearance and the shadows cast from the overshooting tops from a collection of supercells ... the second is an IR shot, but that one doesn't show a lot of differential in IR on cloud temperatures...
Here's a MUCH BETTER EXAMPLE of the Appearance on IR SATELLITE ... Notice the V-NOTCH running west to South of Haysville-Wichita, Kansas on this imagery ... and the warmer cloud top appearance right over Wichita, and Haysville. The cloud tops are ACTUALLY HIGHER and extend into the wamer troposphere (and have punched through the equilibrium level) ...
Another example right over ALABAMA on APRIL 8th, 1998 ... I believe this was a KILLER TORNADO that was rated an F5 ... a VERY CLASSIC V-NOTCH SIGNATURE ON IR IMAGERY ...
