10.8: Accessible Descriptions
- Page ID
- 52333
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Figure 10.1.1: Three Stages of Thunderstorm Development
Three-panel diagram showing the life cycle of a cumulonimbus cloud: towering cumulus stage, mature stage, and dissipating stage. Each panel includes a vertical height scale from the surface up to about 40,000 feet (approximately 12.2 km), with intermediate levels marked at about 10,000 ft (3.0 km), 20,000 ft (6.1 km), and 30,000 ft (9.1 km). A dashed line indicates the freezing level near 32°F (0°C), located around 10,000–15,000 ft (about 3–4.5 km).
In the towering cumulus stage, strong upward motion dominates, with warm air rising from the surface to heights above 20,000 ft (6 km). In the mature stage, the cloud extends to near 40,000 ft (12 km), with both strong updrafts and downdrafts present; precipitation forms and falls, and air circulates within the cloud. In the dissipating stage, downward motion dominates, with downdrafts extending from the upper cloud (around 30,000–40,000 ft or 9–12 km) toward the surface, and the cloud gradually weakens.
The diagram emphasizes that vertical air motion changes from primarily upward (early stage), to mixed upward and downward (mature stage), to primarily downward (dissipating stage), while the cloud reaches its greatest height and intensity during the mature phase.
| Stage | Height range (ft / km) | Dominant motion | Key processes | Cloud characteristics |
|---|---|---|---|---|
| Towering cumulus | Surface to ~20,000+ ft (0–6+ km) | Updrafts | Rising warm air, condensation | Growing vertical cloud |
| Mature stage | Surface to ~40,000 ft (0–12 km) | Updrafts and downdrafts | Precipitation, strong circulation | Fully developed storm |
| Dissipating stage | Surface to ~30,000+ ft (0–9+ km) | Downdrafts | Rainfall dominates, weakening updrafts | Cloud breaks apart |
| Feature | Approx. height (ft) | Approx. height (km) | Temperature reference |
|---|---|---|---|
| Freezing level | ~10,000–15,000 | ~3–4.5 | 0°C (32°F) |
| Mid-cloud region | ~20,000 | ~6.1 | Below freezing |
| Upper cloud top | ~30,000–40,000 | ~9–12 | Much colder |
Figure 10.1.2: Single Celled Thunderstorm Life stages
Wide diagram showing the typical lifecycle of a single-cell thunderstorm over a time span of about 30 minutes, progressing from left to right through cumulus, developing, mature, and dissipating stages. A dashed horizontal line marks the freezing level at 0°C, separating liquid droplets below from ice and snow above.
In the cumulus stage (around 0 minutes), small clouds form with rising air and droplets below the freezing level. In the developing stage, stronger updrafts carry moisture upward above the freezing level, forming snow and ice aloft; moderate precipitation may begin. In the mature stage (roughly mid-lifecycle), the cloud reaches its greatest vertical extent, with strong updrafts and downdrafts occurring simultaneously. Precipitation is heaviest at this stage, including rain below the 0°C level and snow or ice above, and lightning may occur. In the dissipating stage (approaching ~30 minutes), downdrafts dominate, precipitation weakens to light rain or snow, and the cloud gradually spreads and thins.
The diagram shows vertical motions with arrows: upward motion (updrafts) dominating early, both upward and downward motion in the mature phase, and mainly downward motion (downdrafts) in the final stage. Ice is present at higher altitudes above the freezing level, while liquid droplets dominate below.
Figure 10.1.3: Squall line of Thunderstorms
Weather radar image showing precipitation intensity (reflectivity, measured in dBZ) across parts of the central and eastern United States, including Illinois, Indiana, Kentucky, and Ohio. The color scale ranges from about 10 dBZ (very light precipitation) to over 70–80 dBZ (extreme intensity). A narrow, continuous line of strong storms extends from southwest to northeast, roughly from western Kentucky near Murray and Princeton through Evansville and Terre Haute into Indiana. Along this line, reflectivity values reach approximately 50–70+ dBZ, indicating heavy rain and potentially severe thunderstorms.
Behind the line (to the west), a broad area of lighter to moderate precipitation is present, with reflectivity values around 20–40 dBZ. Ahead of the line (to the east), much of Kentucky and southern Indiana shows little or no precipitation, except for a large area—of weak radar returns around Louisville and surrounding regions, generally below about 10–30 dBZ, indicating light precipitation or possibly non-precipitation echoes. Isolated storm cells are visible farther northeast in Indiana and Ohio, with localized reflectivity values around 40–60 dBZ.
Overall, the image shows a squall line with the most intense precipitation along the leading edge, lighter precipitation trailing behind, and mostly clearer conditions ahead of the line.
Figure 10.1.4: Mesoscale Convective System
Weather radar image showing a large, organized mesoscale convective system (MCS) with a curved, rotating appearance. Reflectivity (in dBZ) ranges from about 10 dBZ (very light precipitation) to over 60–70 dBZ (very intense rainfall). Near the center of the system is a region of lower reflectivity (around 0–20 dBZ), not a true eye but an area of weaker precipitation within the storm. Surrounding this region is a broad zone of intense convection, with reflectivity values around 50–70+ dBZ, indicating heavy rain and strong thunderstorms.
Bands and clusters of storms extend outward from the center—especially on one side, with reflectivity values generally between 30 and 60 dBZ, representing moderate to heavy rainfall. Outer areas of the system show lighter precipitation, with values around 10–30 dBZ. Coastlines are visible near the storm, indicating the system is close to land, but the strongest precipitation is concentrated within the convective core and organized bands.
Overall, the image shows a mesoscale convective system with a central region of weaker echoes, surrounded by intense convective cells and organized rainbands, rather than the symmetric structure and clear eye of a tropical cyclone.
Figure 10.1.5: Supercell Thunderstorm Diagram
Diagram of a supercell thunderstorm showing its main structural features from southwest (SW) to northeast (NE). A tall cumulonimbus cloud extends vertically to the upper atmosphere, spreading outward into an anvil near the top, typically around 10 to 12 kilometers in height. Above the anvil, a localized dome called an overshooting top rises slightly higher, indicating strong upward motion. Beneath the anvil on one side are mammatus clouds, which appear as downward bulges associated with turbulent air.
At mid-levels, the main storm tower (cumulonimbus) contains strong updrafts, while a line of smaller growing clouds (flanking line) is located on the southwestern side. Near the surface, the cloud base is uneven, with visible striations indicating rotation. A localized lowering called a wall cloud forms beneath the main updraft region, typically a few hundred meters to about 1 kilometer above the ground. Adjacent to this is a precipitation-free base, while farther northeast a shelf cloud marks the leading edge of cooler outflow air. Beneath the shelf cloud is a region of precipitation, where rain and possibly hail fall to the ground.
Overall, the diagram shows a vertically developed storm with key features including an anvil at about 10 to 12 km, a wall cloud near the surface below 1 km, and precipitation concentrated on the forward (northeast) side.
Figure 10.1.6: Real-life Supercell Thunderstorm
Photograph of a supercell thunderstorm showing a large cumulonimbus cloud with distinct structural features. The cloud extends vertically from near the ground to the upper atmosphere, reaching approximately 10 to 12 kilometers in height. At the top, a flattened anvil spreads outward, with an overshooting top rising slightly higher (around 12 to 13 km), indicating a strong updraft.
On the left side, a flanking line of smaller developing clouds is visible, feeding into the main storm. Near the base of the storm, a lowered region called a wall cloud forms at roughly 0.5 to 1 kilometer above the ground. Beneath this wall cloud, a tornado is present, extending from the cloud base to the surface. To the right of the storm, a region of precipitation is visible, where rain and possibly hail are falling from mid-levels (approximately 2 to 8 km) to the ground.
The image shows a classic supercell structure, with strong vertical development, organized inflow from the flanking line, a rotating wall cloud, and severe weather including a tornado and heavy precipitation.