incus
inc
Cumulonimbus incus
© wetterkurs.ch
Description
The name "incus" (Latin for anvil) describes the characteristic anvil-shaped spread at the top of a cumulonimbus cloud. This forms when the rising air current reaches the tropopause and spreads out horizontally, as it is unable to rise any further. The anvil consists of ice crystals and can extend over many kilometres, often well ahead of the actual thunderstorm cell. Incus is a supplementary feature and occurs exclusively in fully developed thunderstorm clouds.
Identification Features
- Flat, anvil-shaped spread at the top of the cloud
- Fibrous, icy structure in the upper region
- Can extend for kilometres in the direction of the wind
- Clear, sharp boundary at the top
- Dark, towering thunderstorm cloud visible below
- Often recognisable from a great distance
- Indicates that the tropopause has been reached
Related genera
incus is not a distinct cloud type, but a supplementary feature that is given in addition to the genus name. It can occur with the following genera: Cb.
Meteorological Significance
The formation of an incus signals a fully developed, often severe thunderstorm with intense convection. It is a clear warning sign for heavy rainfall, hail, lightning strikes, storm gusts, and in rare cases tornadoes. The anvil indicates the direction of the upper-level wind and frequently announces the approach of the thunderstorm hours in advance. Particularly dangerous are so-called "overshooting tops", which protrude above the anvil and indicate an especially severe thunderstorm.
Facts
- WMO-Code
- inc
- Height layer
- Vertical clouds
- Typical height
- 0.5 - 2.0 km
- Genus
- CUMULONIMBUS