  Various formal blow-up scenarious for the Navier--Stokes equaitons in 3D are
discussed. A particular interest is payed to "twistor mechanisms" based on
angular logarithmic blow-up travelling waves, and to a formation of "blow-up
tornado" about the singular stationary Slezkin--Landau solutions (1934--44) of
a submerged jet. A survey on various related aspects of singularity analysis
for nonlinear parabolic PDEs is enclosed.
