SUPERCELLS

Supercells are storms (typically thunderstorms) which rotate around a vertical axis. Such storms often produce severe weather at ground level (damaging winds, large hail, and/or tornadoes). Further, most strong and violent tornadoes are produced by supercells.

Figure 3.2-18 above shows a supercell photographed from an airplane by Dr. T. Theodore Fujita in 1961. The storm is rotating counterclockwise which is typical for most long-lived supercells in the Northern Hemisphere. Note the striations of clouds in the lower levels curving into the rotating thunderstorm. The anvil formation at the top of the storm is where the storm updrafts reach the stratosphere and stop rising because they lose their buoyancy.

The orange lines on the above figure show how the radar reflectivity echoes from isolated supercells and bow echoes appear on the radar screen. The left panel (a) represents an isolated supercell which often appears as a roughly circular blob with a point or hook on the back side of the echo (in this case on the lower left side). The other three panels (b, c, and d) represent bow echoes which appear bow shaped on the radar screen and are typically larger in scale than isolated supercells. Sometimes supercells will be embedded within the larger bow echo structure.

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