3-25 SNINCR, the depth increase in the past hour, and the total depth of snow on the ground at the time of the report. The depth of snow increase in the past hour and the total depth on the ground are separated from each other by a solidus (/). For example, a snow depth increase of 2 in. in the past hour with a total depth on the ground of 10 in is coded SNINCR 2/10.
3.1.5.13.29 Other Significant Information (Plain Language).
Agencies may add to a report other information significant to their operations, such as information on fog dispersal operations, runway conditions, FIRST or LAST reports from station, etc.
3.1.5.13.30 Additive and Automated Maintenance Data.
Additive data groups (see Table 3-5) are only reported at designated stations and are primarily used by the NWS for climatological purposes. Most have no dir ect impact on the aviation community, but a few are discussed below.
3.1.5.13.31 Hourly Temperature and Dewpoint.
At designated stations, the hourly temperature and dewpoint group are further coded to the tenth of a degree Celsius. For example, a recorded temperature of +2.6 ºC and dewpoint of -1.5 ºC would be coded T00261015.
The format for the coding is as follows:
T Group indicator 0 Indicates the following number is positive; a 1 would be used if the temperature was reported as negative at the time of observation 026 Temperature disseminated to the nearest tenth and read as 02.6 1 Indicates the following number is negative; a 0 would be used if the number was reported as positive at the time of observation 015 Dewpoint disseminated to the nearest tenth and read as 01.5 No spaces are between the entries. For example, a temperature of 2.6 ºC and dewpoint of -1.5 ºC is reported in the body of the report as 03/M01 and the hourly temperature and dewpoint group as T00261015. If the dewpoint is missing, only the temperature is reported; if the temperature is missing, the hourly temperature and dewpoint group are not reported.
3.1.5.13.32 Maintenance Data Groups.
The following maintenance data groups, Sensor Status Indicators and the Maintenance Indicator, are only reported from automated stations.
3.1.5.14 Sensor Status Indicators.
Sensor status indicators are reported as indicated below:
3-26
• If the RVR is missing and would normally be reported, RVRNO is coded.
• When automated stations are equipped with a present weather identifier and the sensor is not operating, the remark PWINO is coded.
• When automated stations are equipped with a tipping bucket rain gauge and the sensor is not operating, PNO is coded.
• When automated stations are equipped with a freezing rain sensor and the sensor is not operating, the remark FZRANO is coded.
• When automated stations are equipped with a lightning detection system and the sensor is not operating, the remark TSNO is coded.
• When automated stations are equipped with a secondary visibility sensor and the sensor is not operating, the remark VISNO LOC is coded.
• When automated stations are equipped with a secondary ceiling height indicator and the sensor is not operating, the remark CHINO LOC is coded.
3.1.5.14.1 Maintenance Indicator.
A maintenance indicator ($) is coded when an automated system detects that maintenance is needed on the system.
3.2 Aircraft Observations and Reports.
There are two kinds of aircraft observations: Pilot Weather Reports (PIREP) and Aircraft Reports, or air-reports (AIREP). Each kind has two types:
• Routine PIREPs and Urgent PIREPs.
• Routine AIREPs and Special AIREPs.
PIREPs are reported by the pilot (or aircrew), while AIREPs can either be reported by the pilot or generated from sensors onboard the aircraft (automated AIREPs). PIREPs and AIREPs are coded differently. The PIREP format is a U.S.-only format. The AIREP format is used worldwide. Automated AIREPs are common over the United States.
3.2.1 Pilot Weather Report (PIREP).
Pilots should report any observation, good or bad, to assist other pilots with flight planning and preparation. If conditions were forecasted to occur but not encountered, a pilot should also report the observed condition. This will help the NWS verify forecast products and create more accurate products for the aviation community.
A PIREP is prepared using a prescribed format (see Figure 3-5, Pilot Weather Report (PIREP) Coding Format). Required elements for all PIREPs are: message type, loca tion, time, altitude/flight level, type aircraft, and at least one other element to describe the reported phenomena. The other elements are omitted when no data is reported. All altitude references are MSL unless otherwise noted. Distance for visibility is in statute miles and all other distances are in nautical miles. Time is reported in UTC.
3-27 Figure 3-5. Pilot Weather Report (PIREP) Coding Format
3.2.1.1 Mes sage Type (UUA/UA).
The two types of PIREPs are Urgent (UUA) and Routine (UA).
3.2.1.1.1 Urgent PIREPs.
Urgent (UUA) PIREPs contain information about:
• Tornadoes, funnel clouds, or waterspouts;
• Severe or extreme turbulence (including Clear Air Turbulence (CAT));
• Severe icing;
• Hail;
• LLWS within 2,000 ft of the surface. LLWS PIREPS are classified as UUA if the pilot reports air speed fluctuations of 10 kts or more, or if air speed fluctuations are not reported but LLWS is reported, the PIREP is classified as UUA;
• Volcanic ash clouds; and/or
• Any other weather phenomena reported that are considered by the briefer as being hazardous, or potentially hazardous, to flight operations.
3.2.1.1.2 Routine PIREPs.
Routine PIREPs are issued after receiving a report from a pilot that does not contain any urgent information as listed in paragraph 3.2.1.1.1.
3.2.1.2 Location (/OV).
The Location (/OV) is the position reference where the phenomenon occurred.
It is not the location of the aircraft when the report is submitted. Location can be referenced either by geographical position or by route segment. A position
3-28 reference is preferred by meteorologists to aid forecast precision, monitoring, and verification.
3.2.1.2.1 Location.
Location can be referenced to a very high frequency (VHF) Navigational Aid (NAVAID) or an airport, using either the three-letter IATA or four-letter ICAO identifier. If appropriate, the PIREP is encoded using the identifier, then three digits to define a radial and three digits to define the distance in nautical miles.
Examples:
/OV APE Over Appleton Very High Frequency Omni-Directional Range Station (VOR) /OV KJFK Over John F. Kennedy International Airport, New York, NY /OV APE230010 230 degrees at 10 NM from the Appleton Very High Frequency Omni-Directional Range Station (VOR) /OV KJFK107080 107 degrees at 80 NM from John F. Kennedy International Airport, New York, NY
3.2.1.2.2 Route Segment.
A PIREP can also be referenced using two or more fixes to describe a route.
Examples:
/OV KSTL-KMKC From Lambert-Saint Louis International Airport, MO to Charles B. Wheeler Downtown Airport, Kansas City, MO /OV KSTL090030-KMKC045015 From 90 degrees at 30 NM from Lambert-Saint Louis International Airport, MO to 45 degrees at 15 NM from Charles B.
Wheeler Downtown Airport, Kansas City, MO
3.2.1.3 Time (/TM).
Time (/TM) is the time that the reported phenomenon occurred or was encountered. It is coded in four digits UTC.
Example:
/TM 1315 1315 UTC
3-29
3.2.1.4 Altitude/Flight Level (/FL).
The altitude/flight level (/FL) is the altitude in hundreds of feet MSL where the phenomenon was first encountered. If not known, UNKN is entered. If the aircraft was climbing or descending, the appropriate contraction (DURC or DURD) is entered in the remarks (/RM). If the condition was encountered within a layer, the altitude range is entered within the appropriate element that describes the condition.
Examples:
/FL085 8,500 ft MSL /FL310 Flight level 310 /FLUNKN /RM DURC Flight level unknown, remarks, during climb
3.2.1.5 Aircraft Type (/TP).
Aircraft type (/TP) is entered. If not known, UNKN is entered. Icing and turbulence reports always include aircraft type.
Examples:
/TP BE20 Super King Air 200 /TP SR22 Cirrus 22 /TP P28R Piper Arrow /TP UNKN Type unknown
3.2.1.6 Sky Condition (/SK).
Sky condition (/SK) group is used to report height of cloud bases, tops, and cloud cover. The height of the base of a layer of clouds is coded in hundreds of feet MSL. The top of a layer is entered in hundreds of feet MSL preceded by the word TOP. If reported as clear above the highest cloud layer, SKC is coded following the reported level.
Examples:
/BKN040-TOP065 Base of broken layer 4,000 ft MSL, top 6,500 ft MSL /SK OVC100-TOP110/ SKC Base of an overcast layer 10,000 ft MSL, top 11,000 ft MSL, clear above /SK OVC015-TOP035/OVC230 Base of an overcast layer 1,500 ft MSL, top 3,500 ft MSL, base of an overcast layer 23,000 ft MSL /SK OVC-TOP085 Overcast layer, top 8,500 ft MSL
3-30 Cloud cover amount ranges are entered with a hyphen separating the amounts,
e.g., BKN-OVC.
Examples:
/SK SCT-BKN050-TOP100 Base of a scattered to broken layer 5,000 ft MSL, top 10,000 ft MSL /SK BKN-OVCUNKN-TOP060/BKN120-TOP150/ SKC Base of a broken to overcast layer unknown, top 6,000 ft MSL, base of a broken layer 12,000 ft MSL, top 15,000 ft MSL, clear above Unknown heights are indicated by the contraction UNKN.
Examples:
/SK OVC065-TOPUNKN Base of an overcast layer 6,500 ft MSL, top unknown. If a pilot indicates he/she is in the clouds, IMC is entered.
/SK OVC065-TOPUNKN /RM IMC Base of an overcast layer 6,500 ft MSL, top unknown, remark, in the clouds. When more than one layer is reported, layers are separated by a solidus (/).
3.2.1.7 Flight Visibility and Weather (/WX).
The pilot reports the weather conditions he or she encounters as follows:
Flight visibility, when reported, is entered first in the /WX field. It is coded FV followed by a two-digit visibility value rounded down, if necessary, to the nearest whole statute mile and appended with SM (FV03SM). If visibility is reported as unrestricted, FV99SM is entered.
Flig ht weather types are entered using one or more of the surface weather reporting phenomena contained in Table 3-2.
Example:
/WX FV01SM +DS000-TOP083/SKC /RM DURC Flight visibility 1 sm, base heavy duststorm layer at the surface, top 8,300 ft MSL, clear above, remarks, during climb
3-31 When more than one form of precipitation is combined in the report, the dominant type is reported first.
Examples:
/WX FV00SM +TSRAGR Flight visibility 0 sm, thunderstorm, heavy rain, hail /WX FV02SM BRHZ000-TOP083 Flight visibility 2 sm, base of a haze and mist layer at the surface, top 8,300 ft MSL If a funnel cloud is reported, it is coded FC following /WX group and is spelled out as Funnel Cloud after /RM group. If a tornado or waterspout is reported, it is coded +FC following /WX group and TORNADO or WATERSPOUT is spelled out after the /RM group.
Examples:
/WX FC /RM FUNNEL CLOUD Funnel cloud, remarks, funnel cloud /WX +FC /RM TORNADO Tornado, remarks, tornado When more than one type of weather is reported, they are reported in the following order:
• TORNADO, WATERSPOUT, or FUNNEL CLOUD.
• Thunderstorm with or without associated precipitation.
• Weather phenomena in order of decreasing predominance.
No more than three groups are used in a single PIREP.
Weather layers are entered with the base and/or top of the layer when reported. The same format as in the sky condition (/SK) group is used.
Example:
/WX FU002-TOP030 Base of a smoke layer, 200 ft MSL, top 3,000 ft MSL
3.2.1.8 Air Temperature (/TA).
Outside air temperature (/TA) is reported using two digits in degrees Celsius.
Negative temperatures is prefixed with an M (e.g., /TA 08 or /TA M08).
3.2.1.9 Wind Direction and Speed (/WV).
Wind direction and speed are encoded using three digits to indicate wind direction, relative to true north, and two or three digits to indicate reported wind speed. When the reported speed is less than 10 kts, a leading 0 is used.
The wind group will always have KT appended to represent the units in knots.
3-32 Examples:
/WV 02009KT Wind 20 degrees at 9 kts /WV 28057KT Wind 280 degrees at 57 kts /WV 350102KT Wind 350 degrees at 102 kts
3.2.1.10 Turbulence (/TB).
Turbulence intensity, type, and altitude are reported after wind direction and speed.
Duration (intermittent (INTMT), occasional (OCNL), or continuous (CONS)) is coded first (if reported by the pilot), followed by the intensity (light (LGT), moderate (MOD), severe (SEV), or extreme (EXTRM)).
Range or variation of intensity is separated with a hyphen (e.g., MOD-SEV).
If turbulence was forecast, but not encountered, negative (NEG) is entered.
Type is coded second. Clear Air Turbulence (CAT) or CHOP is entered if reported by the pilot. High-level turbulence not associated with clouds (including thunderstorms) is reported as CAT.
Altitude is reported (last) only if it differs from value reported in the altitude/flight level (/FL) group. When a layer of turbulence is reported, height values are separated with a hyphen. If lower or upper limits are not defined, BLO or ABV is used.
Examples:
/TB LGT Light turbulence /TB LGT 040 Light turbulence at 4,000 ft MSL /TB OCNL MOD-SEV BLO 080 Occasional moderate to severe turbulence below 8,000 ft MSL /TB MOD-SEV CAT 350 Moderate to severe CAT at 35,000 ft MSL /TB NEG 120-180 Negative turbulence between 12,000 ft and 18,000 ft MSL /TB CONS MOD CHOP 220/NEG 230-280 Continuous moderate chop at 22,000 feet MSL, negative turbulence between 23,000 ft and 28,000 ft MSL /TB MOD CAT ABV 290 Moderate CAT above 29,000 ft MSL
3-33 Turbulence reports should include location, altitude (or range of altitudes), and aircraft type, as well as, when reported, whether in clouds or clear air. The pilot determines the degree of turbulence, intensity, and duration (occasional, intermittent, and continuous). The report should be obtained and disseminated, when possible, in conformance with the Turbulence Reporting Criteria Table in the AIM, Chapter 7, Section 1.
3.2.1.11 Icing (/IC).
Icing intensity, type, and altitude are reported after turbulence.
Intensity is coded first using contractions TRACE, light (LGT), moderate (MOD), or severe (SEV). Reports of a range or variation of intensity is separated with a hyphen. If icing was forecast but not encountered, negative (NEG) is coded. Icing type is reported second. Reportable types are RIME, clear (CLR), or mixed (MX).
The AIM, Chapter 7, Section 1 provides classification of icing intensity according to its operational effects on aircraft, as well as tables of icing types and icing conditions.
The reported icing/altitude is coded (last) only if different from the value reported in the altitude/flight level (/FL) group. A hyphen is used to separate reported layers of icing. Above (ABV) or below (BLO) is coded when a layer is not defined.
Pilot reports of icing should also include air temperature (/TA).
Examples:
/IC LGT-MOD MX 085 Light to moderate mixed icing, 8,500 ft MSL /IC LGT RIME Light rime icing /IC MOD RIME BLO 095 Moderate rime icing below 9,500 ft MSL /IC SEV CLR 035-062 Severe clear icing 3,500 ft to 6,200 ft MSL
3.2.1.12 Remarks (/RM).
The remarks (/RM) group is used to report a phenomenon that is considered important but does not fit in any of the other groups. This includes, but is not limited to, LLWS reports, thunderstorm lines, coverage and movement, lightning, sulfur dioxide (SO2) gas smell, clouds observed but not encountered, and geographical or local descriptions of where the phenomenon occurred. Hazardous weather is reported first. LLWS is described to the extent possible.
3-34
3.2.1.12.1 Windshear.
Ten kts or more fluctuations in wind speed (+/-10KTS), within 2,000 ft of the surface, require an Urgent (UUA) pilot report. When LLWS is entered in a pilot report, LLWS is entered as the first remark in the remarks (/RM) group.
Example:
/RM LLWS +/-15 KT SFC-008 DURC RY22 JFK Remarks, LLWS, air speed fluctuations of plus or minus 15 kts, surface to 800 ft during climb, Runway 22, John F.
Kennedy International Airport, NY.
3.2.1.12.2 FUNNEL CLOUD, TORNADO, and WATERSPOUT.
Funnel cloud, tornado, and waterspout are entered with the direction of movement, when reported.
Example:
/RM TORNADO W MOV E Remarks, tornado west moving east
3.2.1.12.3 Thunderstorm.
Thunderstorm coverage is coded as isolated (ISOL), few (FEW), scattered (SCT), numerous (NMRS) followed by description as line (LN), broken line (BKN LN), solid line (SLD LN), when reported. This is followed with TS, the location and movement, and the type of lightning, when reported.
Example:
/RM NMRS TS S MOV E Remarks, numerous thunderstorms south moving east
3.2.1.12.4 Lightning.
Lightning frequency is coded as occasional (OCNL) or frequent (FRQ), followed by type as lightning in cloud (LTGIC), lightning cloud to cloud (LTGCC), lightning cloud to ground (LTGCG), lightning cloud to air (LTGCA), or combinations, when reported.
Example:
/RM OCNL LTGICCG Remarks, occasional lighting in cloud, cloud to ground
3.2.1.12.5 Electrical Discharge.
For an electrical discharge, DISCHARGE is coded followed by the altitude.
3-35 Example:
/RM DISCHARGE 120 Remarks, discharge, 12,000 ft MSL
3.2.1.12.6 Clouds.
Remarks are used when clouds can be seen but were not encountered and reported in the sky condition group (/SK).
Examples:
/RM CB E MOV N Remarks, cumulonimbus east moving north /RM OVC BLO Remarks, overcast below
3.2.1.12.7 Plain Language.
If specific phraseology is not adequate, plain language is used to describe the phenomena or local geographic locations. Remarks that do not fit in other groups like during climb (DURC), during descent (DURD), reach cruising altitude (RCA), top of climb (TOP or TOC), are included.
Examples:
/RM DONNER SUMMIT PASS
3.2.1.12.8 Volcanic Eruptions.
Volcanic ash alone is an Urgent PIREP. A report of volcanic activity includes as much information as possible including the name of the mountain, ash cloud and movement, height of the top and bottom of the ash, etc., is included.
Example:
/UUA/OV ANC240075/TM 2110/FL370/TP DC10/WX VA/RM VOLCANIC ERUPTION 2008Z MT AUGUSTINE ASH 40S MOV SSE Urgent Pilot Weather Report, 240 degrees at 75 NM from Anchorage International Airport, AK, 2110 UTC, flight level 370, a DC10 reported volcanic ash, remarks, volcanic eruption occurred at 2008 UTC Mount Augustine, ash 40 NM south moving south-southeast.
3.2.1.12.9 SKYSPOTTER.
The SKYSPOTTER program is a result of a recommendation from the Safer Skies FAA/Industry Joint Safety Analysis and Implementation Teams. The term SKYSPOTTER indicates a pilot has received specialized training in observing and reporting in-flight weather phenomenon or PIREPs.
When a PIREP is received from a pilot identifying themselves as a SKYSPOTTER aircraft, the additional comment “/AWC” is added at the end of the remarks section of the PIREP.
3-36 An AWC-WEB/xxxx in the remarks indicates the pilot report was submitted by an airline dispatcher or Center Weather Service Unit (CWSU) meteorologist directly to the Aviation Weather Center (AWC). The xxxx represents the airline abbreviation or Air Route Traffic Control Center (ARTCC) of the CWSU that submitted the PIREP.
Example:
PIREP TEXT/RM REMARKS/AWC
PIREP TEXT/RM REMARKS/AWC-WEB/KZFW
3.2.2 Air-Reports (AIREP).
AIREPs are messages from an aircraft to a ground station. AIREPs are normally comprised of the aircraft’s position, time, flight level (FL), estimated time of arrival (ETA) over its next reporting point, destination ETA, fuel remaining, and meteorological information. It is beyond the scope of this AC to describe the details of all the elements in the AIREP, but this paragraph will focus on the meteorological information.
The AWC’s website provides AIREPs over the CONUS and portions of the Atlantic and Pacific Oceans.
3.2.2.1 AIREP Types and Content.
There are two types of AIREPs, routine or position report (ARP) and special (ARS). AIREPs can be reported by the pilot but the majority of routine AIREPs are automated and downlinked from the aircraft to a service provider,
e.g., a flight planning company, for processing and forwarding to an airline and the NWS.
The majority of AIREPs report wind and temperature at selected intervals along the flight route, derived from onboard sensors and probes. Some aircraft are equipped with sensors and probes to measure humidity/water vapor, turbulence, and icing data.
The format for the AIREP is governed by ICAO. The AWC’s website includes AIREPs on their PIREP Web page that is formatted for Web display with some weather elements decoded.
3.2.2.2 AIREP Examples.
The following examples are from https://www.aviationweather.gov. The actual airline’s call sign was replaced with a fictitiou s call sign and the Special AIREP was created from the routine report.
Routine AIREP Example: