  In view of the growing tension between the dipole anisotropy of number counts
of cosmologically distant sources and of the cosmic microwave background (CMB),
we investigate the number count dipole induced by primordial perturbations with
wavelength comparable to or exceeding the Hubble radius today. First, we find
that neither adiabatic nor isocurvature superhorizon modes can generate an
intrinsic number count dipole. However a superhorizon isocurvature mode does
induce a relative velocity between the CMB and the (dark) matter rest frames
and thereby affects the CMB dipole. We revisit the possibility that it has an
intrinsic component due to such a mode, thus enabling consistency with the
galaxy number count dipole if the latter is actually kinematic in origin.
Although this scenario is not particularly natural, there are possible links
with other anomalies and it predicts a concommitant galaxy number count
quadrupole which may be measurable in future surveys. We also investigate the
number count dipole induced by modes smaller than the Hubble radius, finding
that subject to CMB constraints this is too small to reconcile the dipole
tension.
