Classification of Thunderstorms

Summer in Texas always come with the occasional thunderstorm. Thunderstorms have class, but how do you tell their class?  One storm can have many different types of characteristics. What may look like a pulse storm may, in fact, be a supercell. Storms will come and storms will go, so you may want to understand how classification of thunderstorms work.Classification of thunderstorms a single cell storm

Single Cell Storms

Class one of our classification of thunderstorms.  Single cell storms typically do not produce severe weather and usually last for 20-30 minutes.  This class of storms are also called pulse storms and seem quite random.  Storms of this class can produce severe weather such as downbursts, hail, and heavy rainfall.  Predicting these storms is rather difficult and they usually occur here in the summer months.  True single cell storms are relatively rare since even the weakest of storms usually occur as multicell updraft events.

Multicell Cluster Storms

Class two of our classification of thunderstorms is multicell storms. A multicell cluster consists of a group of cells moving as a single unit, with each cell in a different stage of the thunderstorm life cycle. As the multicell cluster evolves, individual cells take turns at being the most dominant. New cells tend to form along the upwind (typically western or southwestern) edge of the cluster. Mature cells will be located at the center and dissipating cells found along the downwind (east or northeast) portion of the cluster. Multicell severe weather can be of any variety, and generally, these storms are more potent than single cell storms. Actually, the distinction between multicell and single cell storms is not nearly as important as that between multi cells and supercells. The multicell flash flood threat can be significant, in fact, most flash floods probably occur with multicell complexes.

Multicell Lines

Class three of our classification of thunderstorms is multicell lines.  Multicell line storms consist of a line of storms with a continuous,Classification of thunderstorms a multicell storm well-developed gust front at the leading edge of the line.  An approaching multicell line often appears as a dark bank of clouds covering the western horizon.  The great number of closely-spaced updraft/downdraft couplets qualifies this complex as multicellular, although storm structure is quite different from that of the multicell cluster storm. Multicell line storms are better known as squall lines.  Squall lines most frequently produce severe weather near the updraft/downdraft interface at the storm’s leading edge.  Downburst winds are the main threat, although hail as large as golf balls and a gustnado can occur.  Flash floods occasionally occur when the squall line decelerates or even becomes stationary, with thunderstorms moving parallel to the line and repeatedly across the same area.

 

 

Supercell

Class four of our classification of thunderstorms is the supercell. The best definition of a supercell is a thunderstorm with a deep rotating updraft (mesocyclone). Classification of thunderstorms Supercell stormIn fact, the major difference between supercell and multicell storms is the element of rotation in supercells. Even though it is the rarest of storm types, the supercell is the most dangerous because of the extreme weather generated.The flanking line of the supercell behaves differently than that of the multicell cluster storm, in that updraft elements usually merge into the main rotating updraft and then explode vertically, rather than develop into separate and competing thunderstorm cells. In effect, the flanking updrafts “feed” the supercell updraft, rather than compete with it.

Time to practice

In summary, supercells are extremely dangerous and should not be taken lightly. The distinction between supercell and multicell storms is most important, obviously much more so than that between single cell and multicell storms, or between multicell and squall line storms. A few supercells will have the updraft located on the leading southeast (or east) flank.  With any storm you want to take cover as soon as possible even if you believe is is only what we like to call the garden variety.

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