  We present a computation of $\pi^0$ nuclear modification factor with respect
to the reaction plane in Au+Au collisions at $\sqrt{s_{NN}}=200$ GeV, based on
a Monte-Carlo model of elastic energy loss of hard partons traversing the bulk
hydrodynamical medium created in ultrarelativistic heavy-ion collisions. We
find the incoherent nature of elastic energy loss incompatible with the
measured data.
