Evolution of Tornadic Supercell
from early stages of tornado to dissipation
To do this, we "zoom in" and move the
grid system to center it on the wall
cloud and updraft area. The darkly-stippled
precipitation area narrows to the radar pendant
echo, that wraps around the white updraft area
and the white-stippled wall cloud.
reports of strong, warm inflow winds southeast
of the wall cloud suggest a higher tornado risk
than the case where the wall cloud is undercut
by outflow. Indeed, note the symbol "T", for
tornado, and the incipient tornado track (solid
orange line), indicating that a tornado has
Knowledgeable spotters likely will
have reported wall cloud persistence and rapid
motions prior to tornado formation.
We suggest that spotters have a county-wide grid
system and compasses so that wall cloud positions
can be readily triangulated, and that subsequent
inflow and outflow circulation information can be
solicited by the net controllers from spotters who
are in the appropriate geographical locations.
During the mature stage of the tornado,
the rear flank downdraft (RFD) air accelerates, causing the
and flanking line to surge rapidly eastward
relative to the tornado. Damaging winds are
possible along this flanking line gust front,
and small gustnadoes often occur.
radar-indicated precipitation is wrapping
cyclonically around the tornado; and that
the advancing gust front is cutting off warm
air inflow to the tornado. Spotters south
of the tornado probably would witness a sharp
gust front passage.|
The question mark on the accelerating gust front
draws our attention to whether or not a second
wall cloud is beginning to form several miles
east or southeast of the existing tornado. It
is extremely easy to miss such a feature with
all eyes on the pre-existing tornado!
The gust front has completely isolated
the tornado from warm inflow and vortex
dissipation is imminent.
||As the RFD
progressively wraps around the tornado,
it frequently results in a visible "clear slot"
of relatively cloud-free air wrapping cyclonically
around the tornado's south and east sides.
Cold air downbursts impinging upon the tornado
cause the visible funnel cloud to tilt
increasingly from the vertical (usually away
from the rain area). This vortex stretching
is partially responsible for the tornado entering
into the "shrinking" or "rope" stage. It is the
most likely time for the tornado to make left or
right turns from its path, depending on the angle
of attack of cold downbursts on the vortex.
In this example, a new wall cloud has developed
several miles to the inflow side (east or southeast)
of the dissipating tornado. Storm spotters must be
acutely aware of this possible development, which
indicates a possible cyclic supercell storm,
capable of producing more than one tornado.
A repeat of the gust front evolution we have
shown is likely if additional tornadoes develop.