Insydium posts a look into creating a few different twister effects with the X-Particles plugin, making use of the motion modifiers. A home-made tornado rig was the inspiration for using X-Particles’ upwind Modifier for a couple of different results.
The walkthrough covers creating a snow tornado, a twisting school of fish, and then a twister made of liquid, making use of X-Particles meshing.
Insydium made some waves a while back by announcing that they have acquired ExplosiaFX, from BlackCore Technologies. ExplosiaFX is a fluid dynamics simulation tool that was integrated into the now-defunct Autodesk Softimage. ExplosiaFX dynamically uses voxel grids, along with a modern multi-grid solver, offering quality fluid effects within a reasonable compute time, which would be great for creating twister effects like these.