where <Vm> is the mass weighted mean fallspeed of the drop size distributions and <w> is the 6-s mean updraft, positive upwards. We have computed <Vm> from the relation R 0 = K <Vm> M, where M is the rain mass in the drop size distribution, and K is a constant that includes the sample volume and unit conversion (for a typical sample volume of 1,454 liters, K=2.5). Corrections have been made for the decreasing air density aloft. Clearly as <w> approaches <V m>, Rw approaches zero implying that the mass of rain is suspended. In fact, drops having fall speeds less than <w> rise, and conversely for the larger drops. This is analogous to the "balance level" for radar reflectivity where the mean Doppler velocity at vertical incidence is zero (Atlas, l966), except that <Vm> = <w>. This means that the balance level for Z usually occurs somewhat higher than that for M where the updrafts are stronger.