Definition
A PIREP is a report of actual weather conditions encountered in flight, transmitted by a pilot to a Flight Service Station or air traffic controller. It includes details such as location, time, altitude, sky conditions, visibility, temperature, wind, turbulence, icing, and any other significant weather. PIREPs are then distributed to other pilots, briefers, forecasters, and controllers to supplement and verify forecast information.
Plain English
A short message from a pilot describing the weather they are actually seeing and feeling at a given altitude and location. Other pilots and weather services use these reports to know what conditions are really like up there, not just what was predicted.
Context Anchor
Seen in weather briefings, turbulence discussions, aviation weather products, and radio calls when pilots report actual conditions from the aircraft.
Derivation
PIREP is a shortened aviation form of pilot report: “PI” from pilot and “REP” from report. The plural PIREPs simply means more than one pilot report.
Why Pilots Care
Provides immediate, firsthand awareness of hazards like turbulence so pilots can adjust altitude or route before encountering them.
Intuition Check
Do not treat a PIREP as a forecast. A forecast predicts what may happen; a PIREP reports what a pilot actually encountered.
Example Sentence 1
After encountering moderate turbulence at 8,000 feet, the pilot filed a PIREP with Flight Service so other aircraft on the route would be aware.
Example Sentence 2
Before departure the pilot checked PIREPs from aircraft already airborne to confirm cloud tops.