NEXRAD
Current Nexrad
Learn about NEXRAD
NEXRAD or Nexrad (Next-Generation Radar) is a network of 158 high-resolution Doppler weather radars operated by the National Weather Service, an agency of the National Oceanic and Atmospheric Administration (NOAA) within the United States Department of Commerce. Its technical name is WSR-88D, which stands for Weather Surveillance Radar, 1988, Doppler. NEXRAD detects precipitation and atmospheric movement or wind. It returns data which when processed can be displayed in a mosaic map which shows patterns of precipitation and its movement. The radar system operates in two basic modes, selectable by the operator: a slow-scanning clear-air mode for analyzing air movements when there is little or no activity in the area, and a precipitation mode with a faster scan time for tracking active weather. NEXRAD has an increased emphasis on automation, including the use of algorithms and automated volume scans. Second generation NEXRAD radar systems will have the capability to optically detect hailstone size down to the square mile.
Base Reflectivity
Base ReflectivityBase Reflectivity is a measure of the intensity of precipitation occurring, and is reported in units of DBZ. The WSR-88D emits pulses of energy into the atmosphere at regular intervals. When this energy impacts something (i.e. a raindrop, a snowflake, a mountain, etc.), some of the energy is scattered back to the radar dish. NEXRAD base reflectivity data are updated every 5, 6, or 10 minutes, depending on whether the radar is in normal precipitation mode, storm precipitation mode, or clear air mode. The same NEXRAD base reflectivity information (excluding clear air mode data) is incorporated into the WSI NOWrad national and regional mosaics.

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Radial Velocity
Radial VelocityThe Radial Velocity map allows you to view single site Nexrad data for many sectors. Colors indicated the direction of atmospheric particles (raindrop, snowflakes, smoke, dust etc) from the radar site. Green indicates movement towards the radar site and red indicates movement away from the radar site. This is particularly useful in showing rotation within thunderstorms, which may lead to tornadic development. The radar system operates in two basic modes, selectable by the operator: a slow-scanning clear-air mode for analyzing air movements when there is little or no activity in the area, and a precipitation mode with a faster scan time for tracking active weather.

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