NWS Louisville Doppler Radar Composite Reflectivity

Areas of Excessive Heat and Excessive Rainfall Today

Dangerously hot conditions are occurring today in southeast Oklahoma, the ArkLaTex, lower Mississippi Valley, and Puerto Rico. Hot temperatures surround this area throughout the southern U.S. Excessive Heat Warnings and Heat Advisories in effect. Excessive rainfall may lead to flash flooding today over parts of northern Alabama into eastern Tennessee and the Cascades. Read More >

NWS Doppler Radar (WSR-88D) Example Products

While base reflectivity data shows the location and intensity of precipitation at one radar elevation angle (i.e., one plane or "cut" through the atmosphere), "composite reflectivity" (CR) shows the location and highest reflectivity values from all elevation angles (as many as 14 per volume scan) employed by the Doppler radar. In other words, CR is useful to determine the maximum reflectivity value within a thunderstorm without regard to the maximum's vertical location. It also can help identify elevated or suspended high reflectivity cores when used in conjunction with low-level base reflectivity. Large elevated cores can be associated with subsequent hail or strong winds at the surface after the core descends.

In this image, numerous thunderstorms were present on March 2, 2012 over central Kentucky. Red and pink colors represent high CR values within these storms, with the highest values in blue and gray shades within the storms near the center and lower left parts of the image.