Easily Interpretable Bulk Flows: Continuing Tension with the Standard
  Cosmological Model
  We present an improved Minimal Variance (MV) method for using a radial
peculiar velocity sample to estimate the average of the three-dimensional
velocity field over a spherical volume, which leads to an easily interpretable
bulk flow measurement. The only assumption required is that the velocity field
is irrotational. The resulting bulk flow estimate is particularly insensitive
to smaller scale flows. We also introduce a new constraint into the MV method
that ensures that bulk flow estimates are independent of the value of the
Hubble constant $H_o$; this is important given the tension between the locally
measured $H_o$ and that obtained from the cosmic background radiation
observations. We apply our method to the \textit{CosmicFlows-3} catalogue and
find that, while the bulk flows for shallower spheres are consistent with the
standard cosmological model, there is some tension between the bulk flow in a
spherical volume with radius $150$\hmpc\ and its expectations; we find only a
$\sim 2\%$ chance of obtaining a bulk flow as large or larger in the standard
cosmological model with \textit{Planck} parameters
