This is another Houdini12 practice.
I used Pyro FX's volcano and add some turbulence.
Density is 300,600,300.
Rendered by PBR.
It took almost 5hours to make cache and 4hours to render by using iMac 3.4GHz Core i7 with 16GB RAM.
Even though, I do love my iMac, but, I start thinking buying a new work station...