Radar also tries to determine the maximum diameter of hail falling
within a storm cell. The output from this is formatted into inches and
placed in the "Max Size" column of the storm attribute table.
The size that is estimated by radar is usually overdone and the
majority of hail that falls is generally smaller. This is especially
true during the summer months. Therefore, National Weather Service
radar operators tend to only use the maximum hail size to issue
warnings when the probability of severe hail (POSH) is over 50%.
Radar hailstone estimates range from <.50 inch to >4.00
inches in diameter by quarter (.25) increments.
Cells a great distance from the radar site, as well as those which have
just developed, may have an unknown, or undetectable, hail size. Check
the next scan as to if the unknown size has been resolved, as it may
have. If not, try using a different radar site that the storm cell may
be closer to. If a maximum hailstone size is not detectable, or
unknown, the probabilities of hail and severe hail will not be
undetectable as well.
A radar cannot detect the maximum size of hail well, or possibly at
all, if a thunderstorm is close to the radar site. Beams are unable to
extend into the updraft at such a degree from the radar's transmitter.
With that said, it is also possible for storms to weaken. Therefore, it
is a good practice to check the atmospheric conditions before judging
that the "cone of silence" is responsible for the weakening maximum
Never question the decision of an expert meteorologist to issue or
withhold a warning.