NWS Louisville Doppler Radar - Dual Pol Data

Flooding Risks from Tropical Moisture Across the Intermountain West and East Coast

Tropical moisture from Isaias and Rachel will impact portions of the Intermountain West and East Coast states. Flooding, gusty winds and even a threat for severe thunderstorms and tornadoes are possible. Meanwhile, record warmth will spread northward across the Mississippi Valley the next few days. Looking for snow, the first winter storm of the season is underway across the northern Rockies. 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.

Flooding Risks from Tropical Moisture Across the Intermountain West and East Coast

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

NWS Doppler Radar (WSR-88D) Example Products