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Green Line Separater

WSR-88D Low-Level Base Velocity Image The WSR-88D calculates atmospheric motion based on cloud and precipitation movements. It senses motion directed toward and away from the radar, i.e., only motion parallel to a radar beam (radial velocity). Two types of velocity data are available: 1) base velocity which shows movement with respect to the stationary ground and 2) storm-relative velocity map (SRM) data. For more information, consult "Overview of the WSR-88D Radar System."  At left is a low-level base velocity image on May 14, 1995. Green (red) represents radial winds directed toward (away from) the radar located at the small while hole at Ft. Knox in northern Hardin County. An arcing outflow boundary/gust front is evident from central Meade through western Hardin to northern Grayson Counties. The feature is associated with damaging straight-line winds associated with an intense bow echo. However, since actual winds are directed from northwest to southeast across southern Breckinridge and western Hardin Counties, i.e., nearly perpendicular to the radar beam, the radar "thinks" winds are near zero in this area.  Nevertheless, the pattern displayed here, in addition to reflectivity data (not shown) suggested damaging winds along the entire boundary.  

Green Line Separater

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