Stratocumulus radiatus
Sc ra
Stratocumulus radiatus
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Description
The name "radiatus" (Latin: ray-shaped) describes the characteristic arrangement of these clouds in long, parallel bands or rows that appear to radiate from a single point on the horizon and converge toward the opposite horizon. This perspective effect arises from the great extent of the cloud streaks, similar to the way railway tracks appear to meet in the distance. Stratocumulus radiatus consists of large, grey to whitish cloud masses or rolls arranged in striking parallel rows covering the sky. The individual cloud elements may be densely packed or may show gaps through which blue sky is visible. This variety frequently occurs in conditions of uniform airflow in the lower troposphere, which aligns the cloud elements in the direction of the wind.
Identification Features
- Parallel bands or rows of stratocumulus clouds that converge perspectively toward a single point on the horizon
- Cloud elements consist of typical grey-white, flat masses or rolls
- The bands often extend across a large portion of the sky from horizon to horizon
- Individual cloud elements are larger than those of altocumulus (hand-width rule: more than 5 degrees in extent)
- The cloud base is relatively uniform and flat
- Gaps with blue sky are often visible between the bands
- The rows generally run parallel to the prevailing wind direction at cloud level
- Typically grey to whitish coloration with darker undersides on the thicker portions
Occurrence by genus
Highlighted: all genera with which radiatus occurs.
Meteorological Significance
Stratocumulus radiatus indicates a uniform, directed flow in the lower troposphere that organises cloud elements into parallel rows. This cloud form is often associated with stable weather patterns in which a pronounced temperature inversion limits vertical cloud development. Precipitation from stratocumulus radiatus is generally absent or limited to light drizzle. If the cloud bands dissipate during the course of the day, dry weather can usually be expected. If, however, the bands consolidate into a continuous stratocumulus layer, this may indicate an approaching change in weather with increasing moisture.
Facts
- WMO-Code
- Sc ra
- Height layer
- Low clouds
- Typical height
- 0.6 - 2.0 km
- Genus
- STRATOCUMULUS