How to Read PIREPs
Decoding Pilot Reports for turbulence, icing, and real-world weather
Why PIREPs Are Essential
Pilot Reports (PIREPs) are the only source of real-time, in-flight weather observations. While METARs tell you conditions at airports and forecasts predict what might happen, PIREPs tell you what another pilot actually experienced at altitude, right now.
Turbulence, icing, and cloud conditions can vary significantly from forecasts. A PIREP from a pilot who just flew through the area you're about to enter is invaluable information that no forecast can provide.
Remember: No PIREPs doesn't mean good weather—it means no one has reported. In areas with light traffic, dangerous conditions can exist unreported. Conversely, a "negative" PIREP (no turbulence, no icing) is valuable confirmation.
Types of PIREPs
UA - Routine PIREP
Standard pilot report for normal observations: cloud tops and bases, flight visibility, light to moderate turbulence, light icing, temperature, and wind at altitude. Distributed normally through weather systems.
UUA - Urgent PIREP
Immediate distribution for hazardous conditions: severe or extreme turbulence, severe icing, volcanic ash, tornadoes, funnel clouds, waterspouts, hail, or any hazard deemed urgent by the pilot.
PIREP Format Decoded
UA /OV DEN090025 /TM 1545 /FL120 /TP C172 /SK BKN080-TOP100 /TA -08 /WV 27045 /TB MOD /IC LGT RIME 100-120 /RM SMOOTH BELOW 8000
| Element | Code | Meaning |
|---|---|---|
| Type | UA / UUA | Routine / Urgent |
| Location | /OV | Position (fix/radial/distance) |
| Time | /TM | Zulu time of observation |
| Altitude | /FL | Flight level or altitude (hundreds of feet) |
| Aircraft | /TP | Aircraft type |
| Sky | /SK | Cloud layers, bases, tops |
| Temperature | /TA | Outside air temperature (°C) |
| Wind | /WV | Wind direction and speed (dddss) |
| Turbulence | /TB | Turbulence type and intensity |
| Icing | /IC | Icing type, intensity, altitude |
| Remarks | /RM | Additional comments |
Decoding Location (/OV)
The /OV element tells you where the pilot was when they made the observation:
/OV DEN
Over the Denver VOR
/OV DEN090025
25 nautical miles on the 090° radial from Denver VOR
/OV DEN-COS
On the airway between Denver and Colorado Springs
/OV KDEN
Over Denver International Airport
Turbulence Reports (/TB)
| Intensity | Code | Aircraft Reaction |
|---|---|---|
| Light | LGT | Slight, erratic changes. Slight strain against seat belts. |
| Light Chop | LGT CHOP | Rapid, rhythmic bumpiness. No significant changes in altitude. |
| Moderate | MOD | Changes in altitude/attitude. Definite strain against belts. Unsecured objects move. |
| Moderate Chop | MOD CHOP | Rapid bumps with intensity variation. Difficult to read instruments. |
| Severe | SEV | Large, abrupt changes. Aircraft momentarily out of control. Injury possible. |
| Extreme | EXTRM | Aircraft practically impossible to control. Structural damage possible. |
Turbulence Types
Interpreting Turbulence by Aircraft Type
The /TP (aircraft type) matters greatly. What a Boeing 737 reports as "light turbulence" could feel like moderate turbulence in a Cessna 172. Larger, heavier aircraft are less affected. Adjust your expectations based on the reporting aircraft compared to yours.
Icing Reports (/IC)
| Intensity | Code | Description |
|---|---|---|
| Trace | TR | Ice just perceptible. Rate of accumulation slightly greater than rate of sublimation. |
| Light | LGT | Rate of accumulation may create problem for prolonged flight (>1 hr). De-icing equipment handles. |
| Moderate | MOD | Rate of accumulation is significant. Even short encounters become potentially hazardous. Diversion recommended. |
| Severe | SEV | Rate of accumulation is such that de-ice equipment fails to reduce/control. Immediate exit required. |
RIME
Rough, milky, opaque ice. Forms from small supercooled droplets freezing instantly.
CLEAR
Smooth, transparent ice. Forms from large droplets flowing before freezing. Most dangerous.
MIXED
Combination of rime and clear. Rough, uneven surface. Properties of both types.
Example Icing PIREP
/IC MOD RIME 080-100
Moderate rime icing encountered between 8,000 and 10,000 feet. Critical information for non-FIKI aircraft—avoid this altitude band in the area.
Sky Condition Reports (/SK)
PIREPs provide cloud information that ground-based observations cannot: cloud tops, layers between surface and flight levels, and conditions between reporting stations.
/SK OVC025-TOP045
Overcast layer base 2,500 ft, tops 4,500 ft
/SK SCT-BKN040 OVC080-TOP095
Scattered to broken at 4,000; overcast at 8,000 with tops at 9,500
/SK CLR ABV 120
Clear above 12,000 ft (VFR on top above this altitude)
VFR-on-Top Planning
Cloud top reports are invaluable for VFR-on-top planning. A PIREP showing "OVC045-TOP055" tells you VFR conditions exist above 5,500 ft even though the ground is IFR. Combine with TAF cloud forecasts and freezing level to plan altitude.
How to File a PIREP
Filing PIREPs benefits the entire aviation community. Every pilot should file PIREPs, especially for significant weather encounters.
Filing by Radio
Contact any ATC facility (Center, Approach, Tower, or Flight Service):
"Denver Center, Cessna 12345, pilot report."
"Cessna 12345, go ahead with your pilot report."
"Center, Cessna 12345 is 20 miles northeast of Denver VOR at 10,000 feet, Cessna 172. We encountered moderate turbulence between 9,000 and 10,500. Temperature minus 5."
Required Elements
- • Location (over, radial/distance)
- • Time (Zulu)
- • Altitude/Flight Level
- • Aircraft Type
- • Weather phenomenon encountered
Good to Include
- • Outside air temperature
- • Wind at altitude (if known)
- • Cloud tops/bases
- • Flight visibility
- • Negative reports ("no icing")
EFB/App Filing
Most electronic flight bags (ForeFlight, Garmin Pilot, FltPlan Go) support PIREP filing directly from the app. The interface guides you through each element and submits to the National Weather Service. This is often easier than radio filing for non-urgent reports.
When to File PIREPs
Always File (Urgent - UUA)
- • Severe or extreme turbulence
- • Severe icing
- • Tornadoes, funnel clouds, waterspouts
- • Hail
- • Volcanic ash
- • Low-level wind shear
Should File
- • Moderate turbulence or icing
- • Conditions significantly different from forecast
- • Cloud tops/bases useful for planning
- • Visibility restrictions
- • Thunderstorm activity observed
Consider Filing (Negative Reports)
- • Smooth flight when turbulence was forecast
- • No icing when icing was forecast
- • Good visibility/clear conditions
- • Confirming forecast conditions
Negative PIREPs are valuable—they confirm safe conditions for other pilots.
Key Takeaways
- PIREPs provide real-time, in-flight conditions that forecasts can't match
- Consider aircraft type when interpreting turbulence reports
- UUA (urgent) PIREPs indicate hazardous conditions requiring attention
- No PIREPs doesn't mean good weather—it means no reports
- File PIREPs whenever you encounter notable conditions—help others