Simon,
Your question interested me, and I have been through the literature
unsuccessfully to try to confirm my suspicions as to the way that conical
hail forms. Conical hail falls with its broad side down. Hail grows due to
the interception of super-cooled water droplets. One can imagine that if the
droplets are quite large, any initial stable conical falling configuration
will become a tumbling motion, and the resulting stone shape will tend
towards a sphere.This hypothesis would indicate that conical hail will grow
only by intercepting very small cloud droplets. and not larger water drops.
This further indicates that conical hail will most likely form in regions of
cloud that do not have very strong vertical currents. Not a very satisfying
explanation, as there are other aspects that would have to be considered,
such as temperature, cloud liquid content, cloud droplet size, updraught
strength, the presence or otherwise of mixed phase (water and ice) particles
etc.. One thing that can be said is that the stones have become conical
sometime in their growth, and have not encountered anything to disturb them
sufficiently to cause them to tumble, at least not during any growth
episodes.


--
Bernard Burton
Wokingham, Berkshire, UK.

Satellite images at:
www.woksat.info/wwp.html

wrote in message
...
Could not help but notice that much of the large hail that fell in the
Peak District today was conical shaped rather than round. Now these
were not soft hail or small hail, these were true 3 - 5mm hail stones
falling from CBs.
So if these were formed in the normal way hail is supposed to be
formed way were these not round.

Thanks.

Simon (South Yorkshire)