single cell, multicell clusters, multicell lines and supercells

The breakdown into single cell, multicell, and supercell covers the major storm types within the spectrum. One "cell" denotes one updraft/downdraft couplet.

Thus, there are several updrafts and downdrafts in close proximity with a multicell storm. Multicell storms can be broken down further into the categories of multicell line and multicell cluster storms.

The "intense" updraft storm is almost invariably the supercell, a storm capable of producing the most devastating weather, including violent tornadoes.

With the two multicell storm categories, we have defined four basic storm types from the thunderstorm spectrum. The supercell is always severe, whereas the others can be non-severe or severe.

We stress that a "severe" storm is a somewhat arbitrary National Weather Service definition of a storm with one or more of the following elements: 3/4 inch or larger diameter hail, 50 KT downbursts, and tornadoes.

Single cell storms typically do not produce severe weather and usually last for 20-30 minutes. Also known as pulse storms, single cell storms seem quite random (perhaps because of our lack of understanding) in the production of brief severe events such as downbursts, hail, some heavy rainfall, and occasional weak tornadoes.

The "degree of predictability" is extremely low as forecasters are never quite sure which storm will produce severe weather and from which portion of that storm the severe events will occur. However, the microburst threat to aviation cannot be over-emphasized.

This is a single cell storm, looking east from about 15 miles. The storm was moving east (into the photo). Some of the anvil cloud has been left behind the storm, but the greater portion of the anvil is blowing off in advance of the storm and is not observable from this perspective. (May storm in the Texas Panhandle near Amarillo.)