WMOD00590

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

has been restricted largely to interpretations of detailed radar echo
pattern evolution. Many complex cell-environment interactions remain
unexplained, although the importance of vertical wind shear, down-
drafts and entrainment have been recognized, and conceptual and
numerical models incorporating these phenomena have been proposed.

Ludlam (1963) summarized the early conceptual models of deep
moist convection showing the evolution of our three-dimensional
concept of convective development from simple models of Davis (1894)
to the more complex sheared models of Newton (1960, 1966) and Browning
and Ludlam (1962). Browning and Ludlam described the three-
dimensional dynamics of the Workingham storm in which complex inter-
actions between the upper-level flow and strong shear at 10 km and
low-level convergence ahead of a cold front helped maintain a steady-
state system. Newton (1963) summarized much of the research of the
1950ls showing the important interactions between the synoptic-scale
dynamics and the local cloud-scale circulations. Newton used a
technique developed by Clark (1961) to describe the vertical motion
field associated with dry cold fronts. He computed vertical motion
of 70 cm/s just ahead of a squall front and descending motion of
10 to 20 cm/s behind it at the 800-850 mb levels. He recognized the
need to define the relative roles of thermodynamic and dynamic
processes. These distinctions have not yet been fully explored;
hence, our need to systematically study environmental structure for
different storm types, sizes and severity.

Synoptic-scale dynamics associated with upper-level jet streams
and cyclonic development which produced lifting of 100 to 200 mb in

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