How To Read A PIREP: The Ultimate Pilot Guide To Decoding In-Flight Weather Reports

Reading a Pilot Weather Report (PIREP) requires systematically parsing a series of standardized slash-delimited identifiers to extract critical, real-time observations of flight conditions. By translating codes like /OV, /TM, and /FL, pilots can immediately identify actual icing levels, turbulence severity, and cloud bases that automated forecasts might miss. Mastering this decoding process is a foundational safety skill required to maintain situational awareness and navigate hazardous weather boundaries.

Pre-Flight Planning and Critical Aviation Resources

Before attempting to decode a PIREP, you must understand its role within your pre-flight briefing. Unlike Terminal Aerodrome Forecasts (TAFs) or Area Forecasts, which are computer-generated or meteorologist-compiled predictions, a PIREP is an actual, observed report of conditions experienced by flight crews in real time. The Federal Aviation Administration (FAA) processes these reports through the Air Traffic Control (ATC) system and Flight Service Stations (FSS) under FAA Order JO 7110.10.

To make full use of PIREPs during your flight planning, you need a basic set of aviation tools and a solid foundation in standard aeronautical nomenclature.

Essential Equipment and Prerequisite Knowledge

• Required Reference Tools: A current Sectional Aeronautical Chart or IFR Enroute Low Altitude Chart is essential for mapping out the three-letter navigational identifiers (VORs, airports, and fixes) used to plot the position of the report.
• Access to Weather Briefing Platforms: You must have a reliable means to pull current reports, such as the Aviation Weather Center website, Flight Service (1800wxbrief), or an Electronic Flight Bag (EFB) app like ForeFlight or Garmin Pilot.
• Prerequisite Knowledge: You must understand Coordinated Universal Time (UTC/Zulu time), standard flight level formatting (where altitudes are reported in three digits representing hundreds of feet), and the basic principles of aircraft icing and turbulence categories.
• Time Commitment: Mastering the general structure of a PIREP takes roughly 15 to 30 minutes of study, while decoding an individual report during pre-flight preparation takes less than 60 seconds once you memorize the standard system keys.

Decoding the PIREP: Step-by-Step Parsing Workflow

Every PIREP follows a rigid, standardized sequence. By walking through the data field by field, you can easily translate the condensed, abbreviated text into an accurate mental picture of the atmosphere. Let us decode a sample urgent PIREP:

UUA /OV MRB090025 /TM 1430 /FL060 /TP C172 /SK OVC015 /WX FV01SM RA /TA 02 /WV 22015KT /TB LGT /IC LGT RIME /RM DURC

Step 1: Identify the Report Type and Transmission Urgency

The first element indicates the severity and priority of the report.

1. Look at the very beginning of the string for either UA or UUA.
2. UA designates a Routine Pilot Report. These contain standard weather updates, cloud layers, temperatures, and light-to-moderate conditions.
3. UUA designates an Urgent Pilot Report. Air Traffic Control immediately disseminates these reports because they contain hazardous phenomena such as severe turbulence, severe icing, volcanic ash, tornadoes, or low-level wind shear.

In our sample, UUA tells us immediately that this is an urgent report containing potentially hazardous conditions.

Step 2: Plot the Exact Location of the Observation

The location field is prefixed by the /OV identifier.

1. Identify the three-digit or four-digit navigational aid (typically a VOR) or airport identifier directly following the slash.
2. Read the subsequent three digits, which indicate the radial (bearing) from that station in degrees magnetic.
3. Read the final three digits, which indicate the distance from the station in nautical miles (NM).

In our sample, /OV MRB090025 means the aircraft was located on the Martinsburg VOR (MRB) 090-degree radial at a distance of 25 nautical miles.

Pro-Tip: If the location code features only a station identifier (such as /OV KOKC), the pilot reported the conditions directly over that station or airport.

Step 3: Determine the Exact Time of the Report

The time field is prefixed by the /TM identifier.

1. Read the four-digit number immediately following the slash.
2. This number represents the time the observation was made in Coordinated Universal Time (UTC or Zulu), formatted on a 24-hour military clock.

In our sample, /TM 1430 indicates the report was made at 1430 Zulu. Always cross-reference this time with your current time to ensure the information is still fresh and meteorologically relevant.

Step 4: Confirm the Altitude and Flight Level

The altitude field is prefixed by the /FL identifier.

1. Read the three-digit number following the slash, which represents the aircraft’s altitude in hundreds of feet above Mean Sea Level (MSL).
2. If the pilot was in a climb or descent, you might see ranges such as FL020-080 or designations like DURC (during climb) or DURD (during descent).
3. If the altitude is unknown, the report will show FLUNKN.

In our sample, /FL060 indicates the aircraft was flying at 6,000 feet MSL.

Warning: Never assume a pilot report represents surface conditions. Altitude is one of the most critical factors when analyzing icing and turbulence data, as both phenomena are often highly localized to specific atmospheric layers.

Step 5: Identify the Reporting Aircraft Type

The aircraft type field is prefixed by the /TP identifier.

1. Read the alphanumeric code following the slash, which represents the ICAO aircraft designator.
2. Understanding the aircraft type is vital for context. A light aircraft reporting moderate turbulence indicates a very bumpy ride, whereas a heavy Boeing 777 reporting moderate turbulence indicates a much more severe atmospheric disturbance that could be highly dangerous for smaller planes.

In our sample, /TP C172 tells us the reporting aircraft was a Cessna 172 Skyhawk.

Step 6: Parse Sky Cover, Cloud Layers, and Flight Visibility

The sky cover and weather elements are prefixed by the /SK and /WX identifiers.

1. Under /SK, read the sky coverage code (CLR, FEW, SCT, BKN, OVC) followed by a three-digit altitude indicating the cloud base.
2. If the top of the cloud layer was observed, it will be written with TOP followed by the altitude.
3. Under /WX, look for flight visibility (FV) in whole miles, followed by standard METAR precipitation codes (such as RA for rain, SN for snow, or HZ for haze).

In our sample, /SK OVC015 indicates a solid overcast cloud ceiling starting at 1,500 feet MSL. The weather field, /WX FV01SM RA, indicates flight visibility was restricted to 1 statute mile in continuous rain.

Step 7: Analyze Temperature and Wind Velocities

The temperature and wind vectors are prefixed by the /TA and /WV identifiers.

1. Under /TA, read the outside air temperature in degrees Celsius. If the temperature is below zero, it will be prefixed with a minus sign (or sometimes an M).
2. Under /WV, read the first three digits as the true wind direction, followed by the wind speed in knots (KT).

In our sample, /TA 02 shows an air temperature of 2 degrees Celsius, which is dangerously close to freezing. The wind field, /WV 22015KT, shows winds from 220 degrees at 15 knots.

Step 8: Evaluate Turbulence, Icing, and Remarks

The final critical sections are prefixed by /TB, /IC, and /RM.

1. Under /TB, read the turbulence intensity (LGT, MDT, SVR, EXTRM) and type (CHOP or CAT).
2. Under /IC, read the icing intensity (TRACE, LGT, MDT, SVR) and the icing type (RIME, CLEAR, MIXED).
3. Under /RM, read any plain-language remarks written by the pilot or controller to clarify flight conditions, such as DURC (during climb), DURD (during descent), or ZOB (the air route traffic control center handling the report).

In our sample, /TB LGT indicates light turbulence. /IC LGT RIME reports light rime icing. The remarks section, /RM DURC, clarifies that these conditions were encountered during the climb phase of flight.

PIREP Coding and Metric Reference System

The following table provides a comprehensive quick-reference key to decode any standard or urgent PIREP. Use this to quickly translate raw pilot reports during your pre-flight routing.

Handling Common PIREP Decoding Discrepancies

Because PIREPs are inputted manually by Air Traffic Control specialists or Flight Service personnel, they often contain typographical errors, non-standard formatting, or missing fields. When analyzing these reports, look out for these common discrepancies.

Missing Altitude Information

• Root Cause: The pilot failed to report their altitude, or the controller omitted the altitude field (leaving it as FLUNKN or leaving the field out entirely) because of high radio workload.
• Actionable Fix: Cross-reference the pilot's aircraft type and position with nearby airway structures or local traffic patterns. If the report was filed by a Cessna 172 near an airport, assume the report is likely at a lower altitude. If you are already in the air, ask ATC for clarification on the altitude of that specific report.

Non-Standard Location Identifiers

• Root Cause: The report uses a local, non-standard visual reporting point, a small local airport identifier, or an obscure GPS waypoint rather than a standard VOR radial.
• Actionable Fix: Use your Electronic Flight Bag map search function to plot the obscure waypoint. If the waypoint is not on your routing and you cannot locate it, measure the distance to the nearest major VOR listed in the report to estimate whether the weather system lies along your planned path of flight.

Outdated Report Times

• Root Cause: A hazardous weather PIREP (like severe icing or turbulence) remains in the system for several hours because no other aircraft have flown through the area to update or cancel the report.
• Actionable Fix: Check the timestamp (/TM). If the report is more than two hours old, cross-reference it with the current radar, satellite, and SIGMET/AIRMET overlays. Do not assume the hazard has cleared just because the report is old; treat the area with extreme caution until verified by newer reports or ATC.

Mixed or Subjective Turbulence Ratings

• Root Cause: A pilot of a Boeing 737 reports light turbulence, while a pilot of a light sport aircraft reports moderate-to-severe turbulence in the exact same location at the same time.
• Actionable Fix: Always scale the reported turbulence to your own aircraft category. If you are flying a light general aviation aircraft (like a Cessna, Piper, or Cirrus) and see a report of light turbulence from a commercial airliner, prepare for moderate or even severe bumpiness in your aircraft.

Frequently Asked Questions

What is the difference between a UA and a UUA PIREP?

A UA is a routine pilot report containing standard flight conditions, cloud tops, and light weather. A UUA is an urgent pilot report issued for severe or extreme hazards that present an immediate danger to flight safety, such as severe icing, severe turbulence, volcanic ash, or low-level wind shear.

How long does a PIREP remain valid in the aviation system?

A PIREP does not have a formal expiration period like a forecast. However, it is generally considered "active" and highly relevant for up to 2 hours after the observation time. After 2 hours, the data is still useful for identifying structural trends but should be verified using more recent reports or current weather radar.

What does "DURC" and "DURD" mean in a PIREP remarks section?

The abbreviation DURC stands for "during climb," and DURD stands for "during descent." These remarks tell pilots that the reported weather conditions (such as turbulence, icing, or wind shear) were experienced while the aircraft was changing altitude rather than cruising at a constant flight level.

How are wind directions reported in a PIREP?

Unlike surface winds reported in METARs (which are referenced to magnetic north for ATC tower coordination), winds aloft in a PIREP's /WV field are reported relative to true north, matching the standard formatting used in wind and temperature aloft forecasts.

Maximize Flight Safety with Expert Pre-Flight Preparation

Now that you can decode any pilot weather report, you are ready to take command of your pre-flight planning and routing decisions. To build complete confidence before your next flight, match your decoded PIREP data with real-time flight tracking and professional weather planning tools.