Mesoscale convective systems - Severe Convective Storms and Tornadoes: Observations and Dynamics - page 262

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Mesoscale convective systems
''The clouds their backs together laid,
The north begun to push,
The forests galloped till they fell,
The lightning skipped like mice;
The thunder crumbled like a stuff—
How good to be safe in tombs,
Where nature's temper cannot reach,
Nor vengeance ever comes!''
Emily Dickinson—The Clouds their Backs together laid
When convective storms are organized on a scale larger than the convective scale,
their conglomeration is called a ''mesoscale convective system (MCS).'' An MCS is
composed of a contiguous area of precipitation that is 100 km or greater across
in at least one spatial dimension. It is apparent from radar imagery that much of
the area of an MCS seen in satellite imagery 1 is devoid of convective precipitation,
especially when the anvil is very large. MCSs include both isolated/amorphous
complexes of convective storms and squall lines (lines of deep convective cells),
some of which are relatively long, but very narrow, perhaps as long as 100 km or
more and as narrow as 10 km or less.
MCSs undergo evolution in which both their mode of organization and spatial
scale change with time. The individual convective cells that make up at least part
of an MCS are considered to be its building blocks. The building blocks may be
ordinary cells or supercells. MCSs composed of ordinary cells are sometimes
referred to as ''multicell'' complexes, but the latter term could also include regions
1 The term ''mesoscale convective complex (MCC)'' was coined by Bob Maddox in 1980. Based
solely on satellite imagery, MCCs were identified as circularly shaped (as opposed to linearly
shaped) MCSs.