The bounded weak echo region, also known as a BWER or a vault, is a

radar Radar is a detection system that uses radio waves to determine the distance (''ranging''), angle, and radial velocity of objects relative to the site. It can be used to detect aircraft, ships, spacecraft, guided missiles, motor vehicles, w ...

signature within a

thunderstorm A thunderstorm, also known as an electrical storm or a lightning storm, is a storm characterized by the presence of lightning and its acoustic effect on the Earth's atmosphere, known as thunder. Relatively weak thunderstorms are someti ...

characterized by a local minimum in radar

reflectivity The reflectance of the surface of a material is its effectiveness in reflecting radiant energy. It is the fraction of incident electromagnetic power that is reflected at the boundary. Reflectance is a component of the response of the electronic ...

at low levels which extends upward into, and is surrounded by, higher reflectivities aloft. This feature is associated with a strong updraft and is almost always found in the inflow region of a thunderstorm. It cannot be seen visually. The BWER has been noted on radar imagery of severe thunderstorms since 1973 and has a

lightning Lightning is a naturally occurring electrostatic discharge during which two electric charge, electrically charged regions, both in the atmosphere or with one on the land, ground, temporarily neutralize themselves, causing the instantaneous ...

detection system equivalent known as a ''lightning hole''.Martin J. Murphy and Nicholas W. S. Demetriades
An Analysis of Lightning Holes in a DFW Supercell Storm Using Total Lightning and Radar Information.
Retrieved on 2008-01-08.

Description and attributes

The BWER is a nearly vertical channel of weak radar echo, surrounded on the sides and top by significantly stronger echoes. The BWER, sometimes called a vault, is related to the strong updraft in a severe convective storm that carries newly formed atmospheric particulates, called hydrometeors, to high levels before they can grow to radar-detectable sizes. BWERs are typically found at mid-levels of convective storms, to above the ground, and are a few kilometers in horizontal diameter. Identifying the location of the updraft region is important because it is linked to locations where severe weather normally occurs. The presence of a BWER has been part of a method to diagnose thunderstorm strength as part of the

Lemon technique The Lemon technique is a method used by meteorologists using weather radar to determine the relative strength of thunderstorm cells in a vertically wind shear, sheared environment. It is named for Leslie R. Lemon, the co-creator of the current conce ...

since 1977.Leslie R. Lemon. New severe thunderstorm radar identification techniques and warning criteria: a preliminary report. Techniques Development Unit,

National Severe Storms Forecast Center The Storm Prediction Center (SPC) is a US government agency that is part of the National Centers for Environmental Prediction (NCEP), operating under the control of the National Weather Service (NWS), which in turn is part of the National Ocean ...

, Kansas City, Missouri, July 1977. The updraft strength within the BWER supports the growth of large

hail Hail is a form of solid precipitation. It is distinct from ice pellets (American English "sleet"), though the two are often confused. It consists of balls or irregular lumps of ice, each of which is called a hailstone. Ice pellets generally fal ...

stones just above the vault, which can be displaced slightly into the direction of motion of the parent supercell storm.

Detection

The bounded weak echo region (BWER) is a region of low radar reflectivity bounded above by an area of higher radar reflectivity which shows evidence of a strong updraft within mesocyclones. Radar analysts have recognized this phenomenon since at least 1973, using different elevation scans. Methods of objectively corroborating that a BWER is associated with a mesocyclone is done by using a

weather radar Weather radar, also called weather surveillance radar (WSR) and Doppler weather radar, is a type of radar used to locate precipitation, calculate its motion, and estimate its type (rain, snow, hail etc.). Modern weather radars are mostly puls ...

with

Doppler effect The Doppler effect or Doppler shift (or simply Doppler, when in context) is the change in frequency of a wave in relation to an observer who is moving relative to the wave source. It is named after the Austrian physicist Christian Doppler, who d ...

to obtain the precipitations velocities. This have been available operationally in

United States The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country primarily located in North America. It consists of 50 states, a federal district, five major unincorporated territorie ...

since 1997 with the NEXRAD network. When using the lightning detection system, lightning holes (uncovered in 2004) correspond to where a BWER would be seen on radar. A cross-section of the three-dimensional reflectivity of a thunderstorm shows the vault better. Algorithms were developed by the

J.S. Marshall Radar Observatory The J.S. Marshall Radar Observatory (or MRO) is a McGill University facility in Sainte-Anne-de-Bellevue, Quebec, Canada housing several weather radars and other meteorological sensors, many of them running around the clock. It is one of the compon ...

McGill University McGill University (french: link=no, Université McGill) is an English-language public research university located in Montreal, Quebec, Canada. Founded in 1821 by royal charter granted by King George IV,Frost, Stanley Brice. ''McGill Universit ...

Canada Canada is a country in North America. Its ten provinces and three territories extend from the Atlantic Ocean to the Pacific Ocean and northward into the Arctic Ocean, covering over , making it the world's second-largest country by tot ...

to locate the overhang region in a thunderstorm by the late 1980s. Its radar uses 24 angles, giving it good vertical resolution. In United States, fewer scanning angles are made within the WSR-88D radar which makes it more difficult to detect the overhang. Once the overhang is located, it is possible to make a cross-section to view if it is related with a BWER. 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. 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 A plan position indicator (PPI) is a type of radar display that represents the radar antenna in the center of the display, with the distance from it and height above ground drawn as concentric circles. As the radar antenna rotates, a radial tra ...

(PPI).David M. Roth
MCS with Eye - July 21, 2003.
Retrieved on 2008-01-08. When using the lightning detection system, lightning holes (uncovered in 2004) correspond to where a BWER would be seen on radar.

References

External links

North Carolina "Tornadocane" from 1999 - SPC

{{good article Severe weather and convection Radar meteorology

Description and attributes

Detection

See also

References

External links