A supercell is the name of the largest and the most severe forms of thunderstorm. They are also referred to as quasi-steady-state storms because they can remain in the same area for several hours due to a balance in the updraft and downdraft organized within the supercell.
A supercell can be any size ranging from very small to extremely large. Torrential downpours and hail storms producing hail the size of a golf balls are common with supercells and are also thought to spawn the majority of tornadoes with wind speeds that can reach up to 300 miles per hour.
Supercells are rare storms and are very organized. The cell only contains one upward draft, unlike a multi-cell thunderstorm which has several smaller drafts that combine to make one updraft and which all "play" a different part in the make-up of a thunderstorm determining the strength of the storm.
A supercell storm develops when the warm updraft (which is an upward moving current of air) enters into a drier, cooler air in the atmosphere. What you have now is a layer of warm air underneath a layer of dry cool air. When the two layers meet they begin to rotate either in a right or left motion forming a mesocyclone, which is also known as a vortex.
The supercell has six parts;
*Main updraft area
*The wall cloud
The dome is a collection of clouds on the very top of the supercell. It is caused by the updraft pushing the air upward. The main updraft area is where the precipitation gathers.
The wall cloud forms when cool air from the downdraft is pulled into the updraft. This is the area in which tornadoes are most likely to develop because of the quick moving cold air through the updraft area.
The mammatus clouds are the fluffy looking clouds between the dome and the flank line of the cell. There are often present in single cell storms also and have no bearing on the force of a supercell. The precipitation spot is where the rain or hail is held until it descends from the cell. The flanking line is made up of cumulonimbus clouds which are dense and wide and a determining factor is how strong a storm system is.
The above listed parts are what make up the anatomy of a supercell. After a supercell has been established it will fall into one of two categories; Low Precipitation and High Precipitation. Supercells with low precipitation usually don't last long but produce the golf ball size hail. With minimal precipitation a funnel cloud can be spotted easier.
Supercells with high precipitation are the most dangerous thunderstorms producing large amounts of rain which can result in flash floods and hail the size of a tennis ball. Funnel clouds can not be seen forming as the entire cell is surrounded in precipitation.
The anatomy of a supercell is much more complex than the simple description I have provided for you. For more information please visit the websites listed below.