Definition
A component of the NEXRAD weather radar system that takes the raw signals collected by the radar antenna and converts them into the weather products pilots and forecasters actually use, such as reflectivity images, storm tracks, and precipitation estimates.
Plain English
The part of the weather radar system that turns raw radar signals into the weather pictures and data products you see.
Context Anchor
You may see RPG in FAA abbreviation lists, radar facility information, maintenance messages, or NOTAM-related material involving radar service.
Derivation
Radar comes from RAdio Detection And Ranging. Processing means turning raw data into something usable. Group here refers to the bundle of computer equipment that does that work. So an RPG is the computing hardware that processes radar signals into finished weather products.
Why Pilots Care
The weather radar imagery you rely on for preflight planning and inflight decisions doesn't come straight from the antenna -- it comes from the RPG. Knowing this helps you understand why radar products have a slight time lag and why outages at this stage can affect the weather picture you're given.
Intuition Check
Do not read “group” as a group of people here. In this term, it means a grouped set of equipment that works together.
Example Sentence 1
The NEXRAD site collects raw signal data, but it's the RPG that turns it into the reflectivity images shown on the weather briefing.
Example Sentence 2
Technicians verified that the radar processing group was functioning before the new weather product was released.