PIREP's are reports of meteorological phenomena encountered by aircraft in flight.

Format:

UUA or UA indicates the message type - Urgent or Routine

/OV (Over) indicates the location in reference to a VHF NAVAID or an airport, using the three or four alphanumeric identifier and, if appropriate, three digits to define a radial and three digits to define the distance in nautical miles.

Example:

/OV KJFK

/OV KJFK107080

/OV KFMG233016/RM RNO 10SW

Two or more fixes are used to describe a route.

Example:

/OV KSTL-KMKC

/OV KSTL090030-KMKC045015

/TM indicates the time that the reported phenomenon was encountered, recorded in four digits UTC.

Example:

/TM 1315

/FL indicates the altitude or flight level in hundreds of feet (MSL) where the phenomenon was first encountered. The contraction UNKN follows when the flight level is not known. A remark RM may be added if the aircraft was climbing or descending, using the contraction DURC (during climb) or DURD (during descent)

Example:

/FL093

/FL310

/FLUNKN /RM DURC

/TP indicates the type aircraft. If not known, then UNKN follows. Icing and turbulence must always include the type of aircraft.

Example:

/TP AEST

/TP B74A

/TP P28R

/TP UNKN 

/SK indicates the sky condition. Cloud cover is described using the contractions BKN (broken), FEW (few), OVC (overcast), SCT (scattered), and SKC (sky clear). Cloud cover ranges are separated with a hyphen (BKN-OVC). The height of a cloud base layer (if known) is listed in hundreds of feet MSL followed by -TOP and the height of the layer’s top in hundreds of feet MSL or UNKN if the top cannot be determined. A space and SKC follows if the sky is clear above the highest cloud layer. When more than one layer is reported, layers are separated by a solidus /. Reports made from within the clouds state RM IMC in the remarks.

Examples:

/SK OVC015-TOP035/OVC230

/SK OVC-TOP085

/SK TOP090

/SK SCT-BKN050-TOP100

/SK OVC065-TOPUNKN

/SK OVC100-TOP110/ SKC

/SK BKN-OVCUNKN-TOP060/BKN120-TOP150/  SKC

/SK OVC065-TOPUNKN /RM IMC