Mesh deformation simulating a fire

Hi! I have a problem about a feature i am trying to implement. So, lets say we have a flamable wall. (a simple picture of mesh, the red one are verticles)

My idea was to lower the top line verticles by some random small value every frame/click etc. Than we have this:

Yellow ones are lowered verticles, red are ones which are not modified. Problem is with green one. It is lowered to point when its height is the same as the two orange ones. Now, the orange should be lowered, and green should be on this line between two orange. My question is: Is something like this possible? How can i acknowledge which verticles are making which triangles?