Pilot report

A pilot report or PIREP is a report of actual weather conditions encountered by an aircraft in flight. This information is usually relayed by radio to the nearest ground station, but other options (e.g. electronic submission) also exist in some regions. The message would then be encoded and relayed to other weather offices and air traffic service units.

Although the actual form used to record the PIREP may differ from one country to another, the standards and criteria will remain almost the same. At a minimum the PIREP must contain a header, aircraft location, time, flight level, aircraft type and one other field.

In recent years, a PIREP will also include UA or UUA used to identify the PIREP as routine or urgent.

The message identifier "UA" is used when the PIREP contains non-hazardous weather information. If the PIREP contains a report of a tornado, funnel cloud, waterspout, severe turbulence, severe icing, hail, or a low-level wind shear hazard, the identifier "UUA" would be used.

The location (/OV) can be reported in one of three ways: as a direction and distance from a navigation aid (NAVAID), as a direction and distance from an airport, or as the latitude and longitude of the aircraft.

The time (/TM) used is the UTC time that the PIREP is reported.

The flight level (/FL) is reported as either a three digit value that indicates the altitude of the aircraft above sea level in hundreds of feet or can be one of three abbreviations: DURD (during descent or on approach), DURC (during climb or after takeoff) and UNKN (unknown).

Aircraft type (/TP) will be the approved ICAO designator, or UNKN if not reported.

Sky cover (/SK) is used to report the cloud layer amounts and the height of the cloud base. The tops of the cloud layers can also be included, as can more than one layer of cloud. Heights are in hundreds of feet above sea level and are three digits. Abbreviations used in this group are "CLR" (clear), "FEW" (few), "SCT" (scattered), "BKN" (broken) and "OVC" (overcast).

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Wikipedia