Bounded weak echo region
Thebounded weak echo region,also known as aBWERor a vault, is aradarsignature within athunderstormcharacterized by a local minimum in radarreflectivityat low levels which extends upward into, and is surrounded by higher reflectivities aloft, forming a kind of dome of weak echoes. This feature is associated with a strongupdraftand is almost always found in the inflow region of a thunderstorm: it cannot be seen visually.[1]The BWER has been noted on radar imagery of severe thunderstorms since 1973 and has alightningdetection system equivalent known as alightning hole.[2]
Description and attributes
[edit]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, calledhydrometeors,to high levels before they can grow to radar-detectable sizes. BWERs are typically found at mid-levels of convective storms, 3 kilometres (1.9 mi) to 10 kilometres (6.2 mi) above the ground, and are a few kilometers in horizontal diameter.[3]Identifying the location of the updraft region is important because it is linked to locations wheresevere weathernormally occurs.[4]The presence of a BWER has been part of a method to diagnose thunderstorm strength as part of theLemon techniquesince 1977.[5]The updraft strength within the BWER supports the growth of largehailstonesjust above the vault, which is displaced slightly into the direction of motion of the parentsupercellstorm.[6]
Detection
[edit]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,[7]using different elevation scans. Methods of objectively corroborating that a BWER is associated with amesocycloneinvolve using aweather radarwith theDoppler effectto obtain the precipitation velocities. This have been available operationally inUnited Statessince 1997 with theNEXRADnetwork.[8]When using the lightning detection system, lightning holes (uncovered in 2004) correspond to where a BWER would be seen on radar.[2]
A cross-section of the three-dimensional reflectivity of a thunderstorm shows the vault better. Algorithms were developed by theJ.S. Marshall Radar ObservatoryofMcGill UniversityinCanadato locate the overhang region in a thunderstorm by the late 1980s.[9][10][11][12]Its radar uses 24 angles, giving it good vertical resolution.[13]In the United States, fewer scanning angles are made within the WSR-88D radar, which makes it more difficult to detect the overhang.[14][15]Once the overhang is located, it is possible to make a cross-section to view if it is related with a BWER.[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 angleplan position indicator(PPI).[18][19]In the lightning detection system, lightning holes (uncovered in 2004) correspond to locations where a BWER would appear on radar.[2]
See also
[edit]References
[edit]- ^National Weather Service."Bounded Weak Echo Region".Meteorological Glossary.National Oceanic and Atmospheric Administration.Retrieved2008-02-08.
- ^abcMartin 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.
- ^"Bounded Weak Echo Region".Meteorological Glossary.American Meteorological Society.Retrieved2008-02-08.
- ^Advanced Warning Operations Course.IC 3-I-B: 1. Storm Interrogation.Archived2011-07-21 at theWayback MachineRetrieved on 2008-01-08.
- ^Leslie R. Lemon. New severe thunderstorm radar identification techniques and warning criteria: a preliminary report. Techniques Development Unit,National Severe Storms Forecast Center,Kansas City, Missouri, July 1977.
- ^William R. Cotton and Roger A. Pielke.Human Impacts on Weather and Climate.Retrieved on 2008-01-08.
- ^Richard Jason Lynn.The WDSS-II Supercell Identification and Assessment Algorithm.Retrieved on 2008-01-08
- ^Falk, Kenneth; Parker, William."Rotational Shear Nomogram for Tornadoes".Archived fromthe originalon August 21, 2005.Retrieved2008-03-08.
- ^Frédéric Fabry (2007-08-14)."McGill S-band radar severe weather algorithms".McGill University.Wayback Machine.Archived fromthe originalon 2007-08-14.Retrieved2010-06-14.
- ^Duncan, M.R.; Bellon, A.; Kilambi, A.; Austin, G.L.; Biron, H.P. (1992). "PPS and PPS jr: A distribution network for weather radar products, severe warnings and rainfall forecasts.".Preprint.8th International Conference on interactive information and processing systems for Meteorology, Oceanography and Hydrology. Atlanta, Georgia. pp. 67–74.
- ^Austin, G.L.; Kilambi, A.; Bellon, A.; Leoutsarakos, N.; Hausner, A.; Trueman, L.; Ivanich, M. (1986). "Rapid II: An operational, high speed interactive analysis and display system for intensity radar data processing". In American Meteorological Society (ed.).Preprint.23rd Conference on Radar Meteorology and Conference on Cloud Physics. Snowmass, Colorado. pp. 79–82.
- ^Halle, J.; Bellon, A. (1980). "Operational use of digital radar products at the Quebec Weather Centre of the Atmospheric Environment Service, Canada". InAmerican Meteorological Society(ed.).Preprint.19th Radar Meteorology Conference. Miami, Florida. pp. 72–73.
- ^Frédéric Fabry."McGill S-band radar characteristics".McGill University.Archived fromthe originalon 2011-07-06.Retrieved2010-06-14.
- ^Advanced Warning Operations Course.1. Storm Interrogation.Archived2011-07-21 at theWayback MachineRetrieved on 2008-03-08.
- ^Rhonda Scott, Randy M. Steadham, and Rodger A. Brown.New Scanning Strategies for the WSR-88D.Archived2007-01-28 at theWayback MachineRetrieved on 2008-03-08.
- ^Leslie R. Lemon.The Radar “Three-Body Scatter Spike”: An Operational Large-Hail Signature.Retrieved on 2008-03-08.
- ^Valliappa Lakshmanan.The Bounded Weak Echo Region Algorithm.Retrieved on 2008-01-08.
- ^Storm Prediction Center.North Carolina "Tornadocane" from 1999.Retrieved on 2008-01-08.
- ^David M. Roth.MCS with Eye - July 21, 2003.Retrieved on 2008-01-08.
External links
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