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1. Definition
Although supercell occurs less than other thunderstorms, it is the most threatening type of thunderstorm.
This creates gusts, hail, strong precipitation, lightning, and tornadoes. This is a single, powerful cell that can extend vertically to 20 km. These large clouds range in diameter from 20 to 50 km.
2. Formation
There is an capping inversion that prevents the mixing of lower warm, humid air with higher cold, dry air in the troposphere. By surface heating, the temperature and humidity of the air layer trapped under the capping inversion will continue to increase. Eventually, the strong mixture of airs under capping inversion causes the capping inversion to weaken. So, the unstable air with high temperature and humidity erupts, forming an immense supercell.
3. Structure
Mesocyclone
Downdraft
Overshooting top
Cloud base
1) Mesocyclone
: When the southeast wind blows on the ground, the west wind blows on the upper floor, the vertical wind shear creates a rolling motion about a horizontal axis. The strong updrafts in the supercell tilt the horizontally rotating air so that the axis of rotation becomes approximately vertical. This is mesocyclone.
2) Downdraft
: Beneath the cumulonimbus tower, where descending air currents touch the surface, dense, cold air spreads along the ground. The forward boundary of this flowing downdraft acts as a wedge, pushing the warm, wet surface air into the thunderstorm. In this way, the descending airflow maintains the rising airflow to sustain thunderstorms. It can be seen that the cold air flowing out of the descending stream advances into the surrounding warm air and serves as a “mini cold front”.
3) Cloud base
: The supercell cloud base is lowest height being formed the supercell. That is about 2 km. There are precipitation base and precipitation-free base. Also, supercell cloud base has wall cloulds formed near area between the precipitation base and the precipitation-free base. Therefore, there are various phenomena in supercell cloud base.
4) Overshooting top
: An overshooting convective cloud top is a dome-like protrusion above a cumulonimbus anvil, often penetrating the lower stratosphere. It is a manifestation of a very strong updraft in the convective cloud.
Mesocyclone
Analysis
Downdraft
Analysis
Cloud base
Analysis
Overshooting top
Analysis
Analysis
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