You may be seeing an Aircraft Meteorological Data Relay (AMDAR) or an Aircraft Report (AIREP) in the PIREP display.
AMDARs can look as follows:
LVR EU2200 4257N 07023W 312255 F370 MS522 219/054 TB/ S031
In this case, the AMDAR PIREP means:
-LVR = Flight phase: Level flight
-EU2200 = Aircraft ID
-4257N 07023W = Latitude and Longitude Location
-312255 = Date and Time Stamp (31st day at 2255 UTC)
-F370 = Flight Level (37,000 feet)
-MS522 = Temperature (Minus 52.2 degrees C)
-219/054 = Winds (219 at 54kts)
-TB/ = No turbulence
-S031 = Type of weather reporting gear in the plane
AIREPs can look as follows:
ARP BAW89P 5029N 03611W 1024 F410 MS55 273/56
In this case, the AIREP means:
-ARP = Routine AIREP
-BAW89P = Aircraft number.
-5029N = Latitude. Four figures indicating the latitude of the aircraft followed by the letter N (North) or S (South).
-03611W = Longitude. Five figures indicating the longitude of the aircraft followed by the letter E (East) or W (West).
-1024 = UTC time.
-F410 = Flight level (41,000 feet). A four-character group (the letter F followed by three figures), representing the aircraft altitude in hundreds of feet.
-MS55 = Temperature (-55 degrees C). Two figures indicating the temperature in whole degrees Celsius preceded by “PS” (plus) or “MS” (minus).
-273/56 = Wind direction and speed (273 at 56 knots). The first three figures indicate true wind direction in degrees. The last two figures indicate wind speed to the nearest knot.
These automatic reports made by commercial aircraft carrying more precise weather observation gear, and they describe weather conditions in the upper layers of the atmosphere. The data from the reports are fed into NOAA and other worldwide weather service forecast models to improve weather forecasts.