Measurement and interpretation of hailstone density and terminal velocity.

The mass, density, fall velocity and internal structure have been determined for low-density hailstones from an early spring storm in Boulder, Colorado, and drag coefficients calculated. The density of the permeable hail is determined from a new method of volume measurement. The results are compared to those of particles grown in a one-dimensional parcel model using the appropriate sounding. The implications of the results are discussed with reference to hail growth in convective storms.-Authors