NWS Louisville Doppler Radar - Dual Pol Data

Watching Hurricane Erin; Heavy Rainfall Threat for Upper Midwest; Heatrisk for Mississippi Valley

Hurricane Erin continues to track westward with its outer bands bringing heavy rainfall and gusty winds for Puerto Rico and US Virgin Islands. Life-threatening surf and rip currents are occurring and will spread across the Atlantic coasts this week. Meanwhile, heavy rainfall and possible flooding are in the forecast for upper Midwest through Monday. Heatrisk continues for the Mississippi Valley. Read More >

NWS Doppler Radar (WSR-88D) Example Products

Conventional Doppler radar sends out a horizontal energy pulse providing a oneâï¿½ï¿½dimensional view of precipitation. Dual pol radar sends both horizontal and vertical pulses, providing a twoâï¿½ï¿½dimensional view. Thus, it provides much better information about the size, shape, and estimated amount of precipitation, distinguishing between rain, snow, and hail. Basic dual pol products include correlation coefficient (CC), differential reflectivity (ZDR), and specific differential phase (KDP). More information is available on our Dual Pol webpage.

High reflectivity was present in a supercell on March 2, 2012 over central Kentucky (upper left; white arrow). Here, ZDR (upper right) showed low values (white color) indicating spherical shapes suggestive of large hailstones. CC (lower right) showed values of 0.8-0.95 (yellow/green) indicative of a combination of large hail and wet hail/rain. KDP (lower left), which helps assess rain drop size/density, showed a small black area (data dropout), surrounded by values of 1-3 (blue-green). This also denoted large hail, surrounded by small hail and large drops. Thus, dual pol clearly identified large hail in the storm, which produced at least golf ball size. Reflectivity alone (upper left) suggested large hail, but could not confirm it as high values can also mean a lot of small hail and/or a hail/very heavy rain mix.

Watching Hurricane Erin; Heavy Rainfall Threat for Upper Midwest; Heatrisk for Mississippi Valley

NWS Louisville Doppler Radar - Dual Pol Data - 2 March 2012

NWS Doppler Radar (WSR-88D) Example Products