Thunderstorm Types
The single cell
The single cell thunderstorm has a lifetime of only 20-30 minutes.
They usually do not produce severe weather, and can be thought
of as a "garden variety" type storm. They typically
occur on a day with little wind shear. Some single cell
storms with stronger updrafts may produce brief severe weather
events. These storms are capable of producing marginally
severe hail and/or brief downbursts.
The multicell storm
This is the most common type of thunderstorm. It is simply
a collection of single cell storms. Sometimes these multicells
are in clusters, while other times they are organized in
lines (commonly referred to as squall lines). Figure 1
is a horizontal cross section (like a combined radar and satellite
picture) of a squall line. Each cell in the multicell may
last only 20 minutes but the multicell storm may persist for
many hours. These storms are more intense than single cell
storms but are much weaker than supercells. Multicell storms
can produce very heavy rainfall, downbursts with winds up to
about 80 MPH, moderate sized hail up to about golf ball size,
and occasionally weak tornadoes. Figure 2 is a view of
a squall line as seen from above. Squall lines commonly
have gust fronts. The gust front marks the leading
edge of gusty winds from the thunderstorm downdraft.
Near and just behind the gust front is the location
for severe straight-line winds. The heaviest rain and largest
hail occur shortly behind the gust front. The
severe weather most associated with a squall line is damaging
straight-line winds (downburst).
The supercell storm
Supercells are quite rare across Northern Kentucky, the Southwest
half of Ohio, and Southeast and East Central Indiana. However,
when they do occur they pose an extremely high threat to life
and property. What sets the supercell storm apart
from the others is its strong rotation. The intense
updraft of the storm rotates and is called a mesocyclone.
This is the most likely location for tornado formation.
The supercell storm can produce all types of severe weather with
giant hail more than 2 inches in diameter, powerful downbursts
of 100 MPH or more, and strong to violent tornadoes. Figure
3 is a representation of a tornadic thunderstorm as a spotter
might see it when located east of the storm, looking west.
Figure 1.
Figure 2.
Figure 3.