Precipitation shaft

Black storm clouds under which a grey sheet of rain is falling on grasslands.
A rain shaft at the base of a thunderstorm

A precipitation shaft is a weather phenomenon, visible from the ground at large distances from the storm system, as a dark vertical shaft of heavy rain, hail, or snow, generally localized over a relatively small area.

This is different from a virga, which is a shaft of precipitation that evaporates before reaching the ground.

Formation

A precipitation shaft is mostly found underneath convective clouds, like cumulonimbus cloud or cumulus congestus cloud during a downpour storm, as these have well defined vertical drafts (updrafts and downdrafts). However, an advancing nimbostratus cloud could have a diffuse precipitation leading edge.

Developing rain shafts often have a fuzzy, bulbous appearance as they descend. If a source of dry air is present at higher altitude and the air into which the rain is falling is sufficiently warm, then strong, and possibly damaging microbursts are possible.[1]

See also

References

Wikimedia Commons has media related to Praecipitatio.
  1. ↑ "Rain Shaft has a fuzzy, bulbous appearance". Weather World 2010. Retrieved 22 April 2016.
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