WMOD00590

• Title: Analysis and Classification of Mesoscale Cloud and Precipitation Systems
• Date: 8/1/1983
• Weather Modification - Doc Type: Report

Severe convective storms have been considered in terms of a
simple dichotomy developed by Browning, Chisholm, Marwitz and others,
but presented most succinctly by Browning (1978). In this idealiza-
tion, one type of storm is the supercell characterized by a large,
vigorous, steady updraft so strong that there is insufficient time
for precipitation to grow appreciably in its core, and updraft
diameter so large that mixing with the environment is minimal.
Therefore, one of its distinctive features is a region of weak radar
echo that is bounded on its top and all si~es by radar echo of
greater intensity. The organized cirulation in this type of storm is
thought to provide for an extreme precipitation size-sorting such
that the largest particles grow the fastest. For this reason,
supercell storms in general are thought to produce exceptionally
large hail. At the same time, they are proposed to be inefficient as
total precipitation producers because of the updraft strength and its
isolation from particles of the size that can effectively collect the
cloud droplets and bring the water substance down to earth. Browning
and Foote (1976) argued convincingly that the extreme size-sorting in
supercells would make hail suppression by seeding difficult if not
impossible, and that seeding such storms might even produce more
hail.

The second conceptual thunderstorm type is the multicell, which
is envisioned to be composed of an organized series of simple convec-
tive cells, as first described in The Thunderstorm (Byers and Braham,
1949). Each cell has a 30 to 45 min life-cycle, starting with vigor-
ous updrafts and no precipitation and ending with downdrafts and the

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