Outflow (meteorology)

For observers on the ground, a thunderstorm outflow boundary often approaches in otherwise clear skies as a low, thick cloud that brings with it a gust front.

Insects and arthropods are swept along by the prevailing winds, making them good indicators of the presence of outflow boundaries.

[5] Moderate vertical wind shear can lead to the initial development of the convective complex and surface low similar to the mid-latitudes, but it must relax to allow tropical cyclogenesis to continue.

These originate from air that has released its moisture and is expelled at high altitude through the "chimney" of the storm engine.

[8] As air parcels are lifted within the eye of the storm the vorticity is reduced, causing the outflow from a tropical cyclone to have anticyclonic motion.

If wind speeds are high enough, such as during microburst events, dust and sand can be carried into the troposphere, reducing visibility.

[12] Upper-level outflow can consist of thick cirrus clouds which would then obscure the sun and reduce solar insolation around the outermost edge of tropical cyclones.

Radar image animation of an outflow boundary of a storm approaching Tulsa , Oklahoma. The outflow boundary's weak echo moves left-to-right and passes overhead of the Doppler radar station . The outflow produces a gust front that moves ahead of the main thunderstorm.
The outflow boundary indicated by the presence of this shelf cloud preceded a derecho in Minnesota
Outflow boundary that preceded a strong thunderstorm in Oklahoma
Structure of a tropical cyclone. The upper level outflow is depicted by cirrus clouds in the upper part of the schematic
A sandstorm ( Haboob ) approaching Al Asad , Iraq , just before nightfall on April 27, 2005.