Bounded weak echo region

The bounded weak echo region, also known as a BWER or a vault, is a radar signature within a thunderstorm characterized by a local minimum in radar reflectivity at low levels which extends upward into, and is surrounded by higher reflectivities aloft, forming a kind of dome of weak echoes.

[5] The updraft strength within the BWER supports the growth of large hailstones just above the vault, which is displaced slightly into the direction of motion of the parent supercell storm.

Methods of objectively corroborating that a BWER is associated with a mesocyclone involve using a weather radar with the Doppler effect to obtain the precipitation velocities.

[16] However, since 1997, algorithms have been developed by the National Weather Service to determine regions of reflectivity gradient in three dimensions and the presence of BWER in convection.

[17] The development of a pronounced BWER can lead to tropical cyclone-like radar signatures over land when located with a low angle plan position indicator (PPI).

Vertical cross-section through a supercell showing the BWER.
BWER associated with a tornadic supercell in 2006 , as seen from different elevation angles. The lower angles (upper left) shows a weaker area of reflectivity but not at higher levels.
Radar schematics of the BWER