Bounded weak echo region

From Glossary of Meteorology

bounded weak echo region

(Abbreviated BWER.) A nearly vertical channel of weak radar echo, surrounded on the sides and top by significantly stronger echo.

The BWER, sometimes called a vault, is related to the strong updraft in a severe convective storm that carries newly formed hydrometeors to high levels before they can grow to radar- detectable sizes. BWERs are typically found at midlevels of convective storms, 3–10 km above the ground, and are a few kilometers in horizontal diameter.
See also weak echo region.