Definition
A nationwide network of high-power Doppler weather radars operated jointly by the National Weather Service, the FAA, and the Department of Defense. Each WSR-88D site transmits pulses of microwave energy and measures the energy reflected back from precipitation, allowing it to detect rainfall intensity, storm structure, wind motion within storms, and severe weather features such as hail cores, mesocyclones, and gust fronts. Outputs from the network are combined into the composite weather radar imagery pilots see in briefings, on flight service products, and in cockpit weather displays.
Plain English
A network of advanced ground-based weather radars across the United States. They send out radio pulses, listen for the echoes coming back from rain, snow, and hail, and use those echoes to map where precipitation is, how heavy it is, and how the air inside a storm is moving.
Context Anchor
Pilots encounter WSR-88D NEXRAD radar information in weather briefings, aviation weather products, and many cockpit weather displays.
Derivation
WSR-88D stands for Weather Surveillance Radar, 1988, Doppler — the year the design was finalized and the fact that it uses Doppler technology to measure motion, not just precipitation. NEXRAD stands for Next Generation Weather Radar, the program name under which these radars replaced the older 1950s-era weather radars. Knowing the name reminds you that this system measures both where precipitation is and how it is moving.
Why Pilots Care
It supplies the precipitation and storm data that pilots use to avoid turbulence, icing, and convective weather during route planning and in-flight decisions.
Analogy
Think of it like a weather picture taken from the ground and delivered to you after processing. It is very useful for planning and broad avoidance, but it is not the same as seeing the storm live in front of the airplane.
Intuition Check
Do not assume NEXRAD shows exactly what is happening at this instant. It is a processed weather radar picture, so the storm may have moved or changed by the time the pilot sees it.
Example Sentence 1
The preflight briefing showed a line of strong returns on WSR-88D NEXRAD radar moving across the planned route, so the pilot delayed departure by two hours.
Example Sentence 2
After departure the crew monitored updates from the WSR-88D NEXRAD radar to confirm the storm line was moving away from their arrival airport.