The PIREP, the Coded Pilot Weather Report That No Model Can Replicate, and the Icing and Turbulence Intel Every Student Pilot Needs to Learn to Read and File

A Pilot Report (PIREP) is real-time weather data from an actual aircraft flying through the conditions you’re about to enter. When every forecast model says conditions are workable, a single PIREP reporting moderate continuous turbulence at 8,000–12,000 feet directly over your route changes the decision entirely. Learning to read, find, and file them is a core skill before any cross-country flight.

What Is a PIREP and Why Does It Matter?

A PIREP is a real-time weather observation made by a pilot in flight, formatted in a specific coded structure, and submitted to Flight Service or Air Traffic Control for distribution across the aviation weather system.

PIREPs don’t just go to other pilots. They feed the entire weather information chain. The National Weather Service uses them. Forecast models that generate icing outlooks and turbulence forecasts are calibrated against them. Every unexpected icing encounter or turbulence report that doesn’t match the forecast enters the system and improves the picture for every other pilot planning a flight in that air mass.

Ground-based sensors and models can tell you what the atmosphere should be doing. The only way to know what it’s actually doing right now at 9,000 feet over your specific route is to have a pilot fly through it and report back. There is no substitute for that.

What Are the Two Types of PIREPs?

Routine PIREPs are designated UA in the raw coded format. A pilot files one when they have useful information to share - sky conditions, turbulence, icing, winds, visibility, anything that helps another pilot make a better decision.

Urgent PIREPs are designated UUA. These are filed immediately when a pilot encounters severe or extreme turbulence, severe icing, or any condition that poses a significant hazard to flight. Urgent PIREPs receive priority distribution through the National Weather Service and Flight Service. When you see a UUA in your briefing, pay close attention - that pilot just had a serious encounter.

How Do You Read a PIREP? (Field-by-Field Breakdown)

A raw PIREP is a string of slash-separated coded fields. The format is logical once you learn the fields - each begins with a slash and a two-letter identifier.

/OV - Location (“over”) Where the observation was made, expressed as a VOR, airport identifier, or lat/lon position. /OV OKC063064 means the report was filed on the 063-degree radial from the Oklahoma City VOR, 64 nautical miles out.

/TM - Time Coordinated Universal Time (Zulu), four digits. /TM 1522 means 1522Z.

/FL - Flight Level Altitude in hundreds of feet. /FL085 means 8,500 feet. UNKN means the pilot couldn’t determine altitude precisely.

/TP - Aircraft Type More important than it seems. A Cessna 172 reporting moderate turbulence is a very different data point than a Boeing 737 reporting the same thing. Larger, heavier aircraft are less affected by a given turbulence intensity than a light trainer. The Airman Certification Standards (ACS) acknowledge this directly: turbulence intensity is somewhat subjective and aircraft-dependent. Always factor in what kind of airplane made the report.

/SK - Sky Condition Cloud base, tops, and coverage. /SK BKN065 TOP100 means a broken layer from 6,500 feet with tops at 10,000. Forecasts often nail the base but miss the tops. A recent PIREP is frequently your best source for cloud top data - which matters when you’re deciding whether to climb above a layer or how deep a penetration will be.

/WX - Weather Precipitation or other visible phenomena: rain, drizzle, snow, haze.

/TA - Temperature In Celsius. Critical for icing analysis. The temperature field tells you where the freezing level actually is, not just where it’s forecast to be - and those two numbers don’t always agree. If the freezing level is forecast at 8,000 feet and a PIREP shows -2°C at 6,500 feet, the freezing level is lower than expected. That changes your icing exposure significantly.

/WV - Wind Velocity Direction in degrees, speed in knots - the same format as a winds aloft forecast.

/TB - Turbulence Scale: light, moderate, severe, and extreme. Reports also note chop (rapid bumpiness without large altitude deviations, distinct from turbulence producing significant pitch and roll excursions) and whether conditions were continuous or intermittent.

Know these intensity definitions:

• Light: Slight irregular changes, no difficulty controlling the aircraft
• Moderate: Changes in altitude or attitude, aircraft remains in positive control
• Severe: Large, abrupt changes; aircraft may be momentarily out of control
• Extreme: Rarely encountered; capable of causing structural damage

Continuous moderate turbulence across your planned route at your planned altitude requires a real go-no-go decision before you launch. That is not a line to skim.

/IC - Icing Scale: trace, light, moderate, and severe. Ice type also matters:

• Rime ice: White, opaque, forms from small supercooled droplets - typically builds on leading edges and antennas
• Clear ice (glaze ice): Denser, harder to remove, forms from larger supercooled droplets
• Mixed icing: Characteristics of both; often the most challenging to manage

For VFR student pilots in aircraft not certified for flight into known icing, any icing in a PIREP on your route means find an altitude free of that layer - or don’t fly the route.

/RM - Remarks Free text for anything that doesn’t fit the coded fields. “Smooth above 11,000.” “Mountain wave activity present.” “Icing patchy rather than continuous.”

How to Read a Complete PIREP: A Full Example

UA /OV OKC063064 /TM 1522 /FL085 /TP C172 /SK BKN065 TOP100 /TA -4 /WV 35025 /TB LGTCHOP /IC LGT RIME /RM SMOOTH ABV110

Decoded: A Cessna 172 filed a routine PIREP at 1522Z on the 063-degree radial from Oklahoma City VOR, 64 miles out, at 8,500 feet. There’s a broken cloud layer from 6,500 feet with tops at 10,000. Temperature is -4°C. Winds are 350 at 25 knots. Turbulence is light chop. Light rime icing at 8,500 feet. Remarks: smooth above 11,000 feet.

There is a broken layer with tops at 10,000, it’s below freezing in that layer, and light rime icing is present at 8,500. But above 11,000, conditions are smooth and presumably above the icing environment.

For an instrument-rated pilot in an appropriately equipped aircraft, there’s a case for climbing above that layer. For a VFR student in a non-icing-certified trainer, this route at this altitude isn’t happening today.

How Do PIREPs Fit Into Your Weather Briefing?

PIREPs are the ground truth that either confirms or challenges the synthesized forecast picture. If the forecast calls for smooth air at cruise altitude and two recent PIREPs from similar routes at similar altitudes report the same conditions, you have high confidence. If PIREPs are telling a different story than the forecast, that’s a signal to dig deeper before you go.

When the models and the pilot reports disagree, the PIREPs usually win. The model is working from physics and statistics. The PIREP is working from actual air.

One important caveat: PIREPs work best for stable icing environments and mechanical turbulence. For rapidly developing convective situations, a PIREP can become outdated in minutes. A thunderstorm complex that was 50 miles north of your route an hour ago may be directly over it now. For convective weather, PIREPs are useful context - but they don’t replace radar and satellite, and they can’t predict what a developing cell is about to do.

PIREPs also have coverage gaps. Over busy corridors, a dozen reports may paint a detailed picture. Over a remote stretch of the northern plains on a Tuesday afternoon, you may find one report from two hours ago - or nothing at all.

Absence of a PIREP is not evidence of good conditions. It may simply mean nobody flew that route recently.

Age matters. A report from three hours ago is useful context, not current intelligence. One from 20 minutes ago from a pilot flying your route in the opposite direction is about as real-time as it gets. The FAA treats PIREPs as representative of conditions within roughly one hour and 100 nautical miles of the reported position. In rapidly changing conditions, compress that window significantly.

Where Can You Find PIREPs?

• Flight Service (1800wxbrief.com): PIREPs appear in the pilot reports section of any standard briefing
• ForeFlight and similar EFB apps: Display PIREPs as map icons with a decoded tap-view; the geographic overlay shows distribution relative to your route and altitude
• Aviation Weather Center (aviationweather.gov): PIREP viewer with filters for type, intensity, altitude range, and time window - bookmark this one
• ATC / Flight Following: Once airborne, request PIREPs along your route directly from the controller - or from Flight Service on 122.2

You don’t have to fly into uncertainty once you’re in the air. The information is available. Ask for it.

How Do You File a PIREP Yourself?

When you encounter something significant - unexpected icing, turbulence worse than forecast, cloud tops or bases different from your briefing, visibility lower than reported - call it in. That information is immediately useful to every pilot behind you on that route.

To file verbally, call ATC on your current frequency or Flight Service on 122.2. You don’t need to know the coded format. A simple call sounds like this:

“Kansas City Center, Skyhawk four-five-lima, I’d like to file a PIREP. Moderate turbulence continuous at nine thousand five hundred, about forty miles east of Wichita.”

The controller will encode it and ask any follow-up questions needed. Some EFB applications also support direct PIREP filing, routing your report through Flight Service to the same distribution network.

That report reaches every pilot and briefer pulling weather in the area for the next hour. One call. Two minutes. Potentially significant to a lot of people.

What Do Examiners Expect You to Know About PIREPs for the Checkride?

The ACS for the private pilot certificate includes weather briefing as a tested area. Your examiner will expect you to interpret key PIREP fields, explain icing and turbulence intensity scales in practical terms, and integrate PIREP data into a go-no-go decision.

Common oral questions include:

• “Here are the PIREPs along this route at your planned altitude - what are your concerns?”
• “You’ve planned to cruise at 8,500 feet and you see this report - walk me through your thinking.”

Practice answering those with real current data before your checkride. Pull up the weather for any cross-country route, read the PIREPs first, then check the models. See where they agree and where they diverge. Over time you’ll develop real intuition for reading an air mass from pilot report data alone.

Chapter 7 of the Aeronautical Information Manual (AIM) is the primary reference. The Aviation Weather Center at aviationweather.gov has the live PIREP feed and a solid decoder guide.

Key Takeaways

• A PIREP is real-time weather from an actual aircraft - no forecast model can replicate it, and it calibrates the entire aviation weather information chain
• UA = routine PIREP; UUA = urgent PIREP - treat any UUA as a high-priority alert
• The /TP (aircraft type) field matters: turbulence that’s moderate in a 737 may be severe in a Cessna 172
• Absence of a PIREP is not evidence of good conditions - it often just means the route is underreported
• For VFR students in non-icing-certified aircraft, any icing in a PIREP on your route means find an alternate altitude or don’t fly the route
• File PIREPs yourself - one radio call distributes real-time conditions to every pilot and briefer in the area for the next hour