Ordinary-cell convective storms - Severe Convective Storms and Tornadoes: Observations and Dynamics - page 113

Figure 3.17. Cumulonimbus (developing supercell) with a symmetrical, mushroom-like anvil,
on May 26, 1997 in eastern Oklahoma (photograph by the author).
wind shear, or if there is strong vertical shear but the storm is viewed from the
rear, the anvil takes on a mushroom-like appearance ( Figure 3.17 ). When anvil
material in the form of ice crystals is left behind after the updraft that was
responsible for it has dissipated, the cloud mass is referred to as ''orphaned anvil''
(Walter Hitschfeld at McGill is credited with this moniker from a paper published
in 1960) ( Figure 3.18 ).
The observed life cycle of an ordinary-cell convective storm ( Figure 3.19 ) is
less than an hour, the time it takes buoyant air to travel from the boundary layer
(the source of the updraft air; if the source is above the boundary layer, then the
convective storm is said to be ''elevated'' and the observed life cycle should be
shorter) all the way to the tropopause and then fall to the ground as precipitation
(the total time elapsed is the ''advective'' time scale). The updraft region in a con-
vective storm is called a ''cell''. The identical terminology is used to describe the
precipitation region detected by a meteorological radar (radar echo). Since each
region of precipitation was once associated with an updraft, one-to-one correspon-
dence can be made between the updraft cell and the radar-observed precipitation
cell, even though in the latter there may not be any updraft remaining.
Horace Byers and Roscoe Braham were the first to describe the life cycle of an
ordinary-cell convective storm 1 based on observations during the Thunderstorm
1 See Ludlam (1963, Fig. 1) for a summary of earlier conceptual models going as far back as the
late 19th century.