  For the steady-state direct cascade of two-dimensional Navier-Stokes
turbulence, we derive analytically the probability of strong vorticity
fluctuations. The probability density function (pdf) of the vorticity
coarse-grained over a scale in the inertial interval is shown to have a
universal self-similar form, in distinction from other known direct cascades.
The tails of the pdf are found to be exponential.
