| The multicell cluster is the most common type
of thunderstorm. The multicell cluster consists of a group of cells, moving along as
one unit, with each cell in a different phase of the thunderstorm life
cycle. As the cluster moves along, each cell takes its turn as the dominant cell in
the cluster. New cells tend to form at the upwind (usually western or southwestern)
edge of the cluster. Mature cells are usually found at the center of the cluster
with dissipating cells at the downwind (usually eastern or northeastern) edge of the
cluster. See figures 8 and 9 for schematic
diagrams of multicell cluster storms. Although
each cell in a multicell cluster lasts only about 20 minutes (as with a single cell
storm), the multicell cluster itself may persist for several hours. Multicell
clusters are usually more intense than single cell storms but are much weaker than
supercell storms. Multicell cluster storms can produce heavy rainfall (especially if
a number of cells mature over the same area), downbursts (with wind speeds up to about 80
miles an hour), moderate-sized hail (up to about golfball size), and occasional weak
tornadoes. Severe weather will tend to occur where updrafts and downdrafts are close
to each other (i.e., near the updraft-downdraft interface (UDI) associated with mature cells). |
| .. .
. |
| Figure 8:
Propagation of a multicell cluster storm. Cloud outlines and radar echo intensities are
shown |
|
