How to read a PIREP

A PIREP is the weather that no instrument on the ground can measure: what a pilot actually felt and saw at altitude, passed on so the next aircraft is not surprised.

This is general educational information, not operational, legal, or regulatory advice. Rules differ by authority and change over time. Always verify against current official sources and follow your operator's approved procedures.

What a PIREP is for

Surface observations and forecasts are powerful, but they cannot directly see the turbulence at FL080, the height of the cloud tops, or the icing inside a layer. A PIREP (pilot report) fills that gap with first-hand information from someone who has just flown through it. The FAA Aeronautical Information Manual sets out the coding (paragraph 7-1-18, Pilot Weather Reports), and the NOAA/NWS Aviation Weather Center collects and distributes them. Internationally, the equivalent is the air-report (AIREP), defined under ICAO Annex 3 and ICAO Doc 4444, with a special air-report used for hazards encountered en route.

A PIREP comes in two types. UA is a routine report. UUA is urgent, reserved for the conditions other pilots most need to hear about quickly: severe or extreme turbulence, severe icing, hail, low-level wind shear, volcanic ash, and similar threats.

A worked example

Here is a routine PIREP in the slash-coded form used in the United States:

UA /OV BUF 270010 /TM 1645 /FL080 /TP BE20 /SK BKN035-TOP070 /TA M04 /WV 28030 /TB MOD /IC LGT-MOD RIME /RM TOPS 070

Reading it field by field:

• UA is the report type: a routine pilot report.
• /OV BUF 270010 is the location: over a point 10 nautical miles out on the 270 bearing from the Buffalo (BUF) navaid. The /OV field is always given relative to a fix or navaid, not as bare coordinates.
• /TM 1645 is the time: 1645 UTC. Like every aviation time, it is UTC, not local.
• /FL080 is the altitude: flight level 080, or 8000 ft.
• /TP BE20 is the aircraft type, a Beechcraft King Air. The type matters, because moderate turbulence in a light twin and in an airliner are not the same experience.
• /SK BKN035-TOP070 is the sky cover: broken cloud with a base near 3500 ft and tops near 7000 ft.
• /TA M04 is the outside air temperature: minus 4 degrees C. As in a METAR, the M prefix marks a negative value.
• /WV 28030 is the wind: from 280 degrees at 30 knots.
• /TB MOD is the turbulence: moderate.
• /IC LGT-MOD RIME is the icing: light to moderate rime ice.
• /RM TOPS 070 is the remarks field, here noting the cloud tops at 7000 ft.

The five mandatory fields, present in every PIREP, are the type, /OV, /TM, /FL, and /TP; the rest are added as the pilot has something to report.

The fields in full

The complete set of element identifiers, per the FAA and the Aviation Weather Center, is:

• /OV location, /TM time, /FL altitude or flight level, /TP aircraft type (the mandatory core);
• /SK sky cover and cloud tops, /WX flight visibility and weather, /TA temperature, /WV wind, /TB turbulence, /IC icing, and /RM remarks.

Turbulence and icing are reported by intensity (light, moderate, severe, and for turbulence extreme) and, for icing, by type (rime, clear, or mixed), which mirrors the icing types used in the forecast products.

ICAO and the US coding

The hazards a PIREP reports are universal, but the slash-coded /OV, /TM, /FL format is the FAA encoding used in the United States. Under the ICAO system the same information travels as an air-report (AIREP), structured around position, time, flight level, and the observed conditions, with a special air-report (AIREP SPECIAL) raised for hazardous weather met in flight, as set out in ICAO Doc 4444 and ICAO Annex 3. The content is comparable; the layout on the page is not, so do not expect the slash fields everywhere.

Common pitfalls

• The altitude is where the condition was met, not a forecast band. A turbulence PIREP at /FL080 says nothing about FL120.
• /OV is relative to a navaid, so you need to know where that navaid is to place the report on your route.
• Aircraft type sets the scale. Weigh a turbulence or icing report against the size and type of the aircraft that filed it.
• A PIREP is a snapshot, valid for the moment it was taken; conditions aloft move and change, so treat an older report with appropriate caution.

In Pilot EFB

Pilot EFB pulls the weather for your route and shows the decoded report alongside the raw text, with the raw report always kept and never replaced, so the briefing reads in plain language while the original coding stays available. A briefing you have already pulled stays readable with no signal, because your device holds what you have saved; fetching fresh reports needs a connection. Pilot EFB is offline-first and is not a certified Electronic Flight Bag, so brief the weather from your official source of record.