3-18 Remarks are included in METAR and SPECI, when appropriate.
Remarks are separated from the body of the report by the contraction RMK.
When no remarks are necessary, the contraction RMK is not required.
METAR/SPECI remarks fall into two categories: (1) Automated, Manual, and Plain Language, and (2) Additive and Automated Maintenance Data.
Table 3-5. METAR/SPECI Order of Remarks Automated, Manual, and Plain Language
1. Volcanic Eruptions
2. Funnel Cloud
3. Type of Automated Station
4. Peak Wind
5. Wind Shift
6. Tower or Surface Visibility
7. Variable Prevailing Visibility
8. Sector Visibility
9. Visibility at Second Location
10. Lightning
11. Beginning and Ending of Precipitation
12. Beginning and Ending of Thunderstorms
13. Thunderstorm Location
14. Hails tone Size
15. Virga
16. Variable Ceiling Height
17. Obscurations
18. Variable Sky Condition
19. Significant Cloud Types
20. Ceiling Height at Second Location
21. Pressure Rising or Falling Rapidly
22. Sea-Level Pressure
23. Aircraft Mishap
24. No SPECI Reports Taken
25. Snow Increasing Rapidly
26. Other Significant Information Additive and Automated Maintenance Data
27. Precipitation amount within a specified time period*
28. Cloud Types*
29. Duration of Sunshine*
30. Hourly Temperature and Dewpoint
31. 6-Hourly Maximum Temperature*
32. 6-Hourly Minimum Temperature*
33. 24-Hour Maximum and Minimum Temperature*
34. 3-Hourly Pressure Tendency*
35. Sens or Status Indicators
36. Maintenance Indicator Note: Additive data is primarily used by the National Weather Service for climatological purposes.
*These groups should have no direct impact on the aviation community and will not be discussed in this document.
Remarks are made in accordance with the following:
• Time entries are made in minutes past the hour if the time reported occurs during the same hour the observation is taken. Hours and minutes are used if the hour is different.
• Present weather coded in the body of the report as VC may be further described (e.g., direction from the station, if known). Weather phenomena beyond 10 sm of the point(s) of observation are coded as distant (DSNT) followed by the direction from the station. For example, precipitation of unknown intensity within 10 sm east of the station would be coded as VCSH E; lightning 25 sm west of the station would be coded as LTG DSNT W.
3-19
• Distance remarks are in statute miles except for automated lightning remarks, which are in nautical miles (NM).
• Movement of clouds or weather, when known, is coded with respect to the direction toward which the phenomena are moving. For example, a thunderstorm moving toward the northeast would be coded as TS MOV NE.
• Directions use the eight points of the compass coded in a clockwise order.
• Inso far as possible, remarks are entered in the order they are presented in the following paragraphs (and Table 3-5, METAR/SPECI Order of Remarks).
3.1.5.13 Automated, Manual, and Plain Language Remarks.
These remarks generally elaborate on parameters reported in the body of the report. An automated station or observer may generate automated and manual remarks. Only an observer can provide plain language remarks.
3.1.5.13.1 Volcanic Eruptions (Plain Language).
Volcanic eruptions are coded in plain language and contain the following, when known:
• Name of volcano;
• Latitude and longitude or the direction and approximate distance from the station;
• Date/Time (UTC) of the eruption;
• Size description, approximate height, and direction of movement of the ash cloud; and
• Any other pertinent data about the eruption.
For example, a remark on a volcanic eruption would look like the following:
RMK MT. AUGUSTINE VOLCANO 70 MILES SW ERUPTED AT 231505 LARGE ASH CLOUD EXTENDING TO APRX 30000 FEET MOVING NE.
Pre-eruption volcanic activity is not coded. Pre-eruption refers to unusual and/or increasing volcanic activity which could presage a volcanic eruption.
3.1.5.13.2 Funnel Cloud.
At manual stations, tornadoes, funnel clouds, and waterspouts are coded in the following format: tornadic activity, TORNADO, FUNNEL CLOUD, or WATERSPOUT, followed by the beginning and/or ending time, followed by the location and/or direction of the phenomena from the station, and/or movement, when known. For example, TORNADO B13 6 NE would indicate
3-20 that a tornado began at 13 minutes past the hour and was 6 sm northeast of the station.
3.1.5.13.3 Type of Automated Station.
AO1 or AO2 is coded in all METAR/SPECI from automated stations.
Automated stations without a precipitation discriminator are identified as AO1; automated stations with a precipitation discriminator are identified as AO2.
3.1.5.13.4 Peak Wind.
Peak wind is coded in the following format: the remark identifier PK WND, followed by the direction of the wind (first three digits), peak wind speed (next two or three digits) since the last METAR, and the time of occurrence. A space is between the two elements of the remark identifier and the wind direction/speed group; a solidus (/), without spaces, separates the wind direction/speed group and the time. For example, a peak wind of 45 kts from 280 degrees that occurred at 15 minutes past the hour is coded PK WND 28045/15.
3.1.5.13.5 Wind Shift.
Wind shift is coded in the following format: the remark identifier WSHFT, followed by the time the wind shift began. The contraction FROPA is entered following the time if there is reasonable data to consider the wind shift was the result of a frontal passage. A space is between the remark identifier and the time and, if applicable, between the time and the frontal passage contraction. For example, a remark reporting a wind shift accompanied by a frontal passage that began at 30 minutes after the hour would be coded WSHFT 30 FROPA.
3.1.5.13.6 Tower or Surface Visibility.
Tower or surface visibility is coded in the following format: tower (TWR VIS) or surface (SFC), followed by the observed tower/surface visibility value. A space is coded between each of the remark elements. For example, the control tower visibility of 1½ sm would be coded TWR VIS 1 1/2.
3.1.5.13.7 Variable Prevailing Visibility.
Variable prevailing visibility is coded in the following format: the remark identifier VIS, followed by the lowest and highest visibilities evaluated, separated by the letter V. A space follows the remark identifier and no spaces are between the letter V and the lowest/highest values. For example, a visibility that was varying between ½ and 2 sm would be coded VIS 1/2V2.
3.1.5.13.8 Sector Visibility (Plain Language).
Sector visibility is coded at manual stations in the following format: the remark identifier VIS, followed by the sector referenced to eight points of the
3-21 compass, and the sector visibility in statute miles. For example, a visibility of 2½ sm in the northeastern octant is coded VIS NE 2 1/2.
3.1.5.13.9 Visibility at Second Location.
At designated automated stations, the visibility at a second location is coded in the following format: the remark identifier VIS, followed by the measured visibility value and the specific location of the visibility sensor(s) at the station. This remark will only be generated when the condition is lower than that contained in the body of the report. For example, a visibility of 2½ sm measured by a second sensor located at Runway 11 is coded VIS 2 1/2 RWY11.
3.1.5.13.10 Lightning.
When lightning is observed at a manual station, the frequency, type of lightning, and location are reported. The contractions for the type and frequency of lightning are based on Table 3-6, METAR/SPECI Type and Frequency of Lightning, for example, OCNL LTGICCG NW, FRQ LTG VC, or LTG DSNT W.
When lightning is detected by an automated system:
• Within 5 NM of the Airport Location Point (ALP), it is reported as TS in the body of the report with no remark.
• Between 5 and 10 NM of the ALP, it is reported as VCTS in the body of the report with no remark.
• Beyond 10 but less than 30 NM of the ALP, it is reported in remarks only as LTG DSNT followed by the direction from the ALP.
Table 3-6. METAR/SPECI Type and Frequency of Lightning Type of Lightning Type Contraction Definition Cloud-ground CG Lightning occurring between cloud and ground In-cloud IC Lightning which takes place within the cloud Cloud-cloud CC Streaks of lightning reaching from one cloud to another Cloud-air CA Streaks of lightning which pass from a cloud to the air, but do not strike the ground Frequency of Lightning Frequency Contraction Definition Occasional OCNL Less than 1 flash/minute Frequent FRQ About 1 to 6 flashes/minute Continuous CONS More than 6 flashes/minute
3-22
3.1.5.13.11 Beginning and Ending of Precipitation.
At designated stations, the beginning and ending times of precipitation are coded in the following format: the type of precipitation, followed by either a B for beginning or an E for ending, and the time of occurrence. No spaces are coded between the elements. The coded times of the precipitation start and stop times are found in the remarks section of the next METAR. The times are not required to be in the SPECI. The intensity qualifiers are coded. For example, if rain began at 0005 and ended at 0030, and then snow began at 0020 and ended at 0055, the remarks would be coded RAB05E30SNB20E55. If the precipitation was showery, the remark is coded SHRAB05E30SHSNB20E55. If rain ended and snow began at 0042, the remark would be coded as RAESNB42.
3.1.5.13.12 Beginning and Ending of Thunderstorms.
The beginning and ending times of thunderstorms are coded in the following format: The thunderstorm identifier TS, followed by either a B for beginning or an E for ending, and the time of occurrence. No spaces are between the elements. For example, if a thunderstorm began at 0159 and ended at 0230, the remark is coded TSB0159E30.
3.1.5.13.13 Thunderstorm Location.
Thunderstorm locations are coded in the following format: the thunderstorm identifier TS, followed by the location of the thunderstorm(s) from the station, and the direction of movement, when known. For example, a thunderstorm southeast of the station and moving toward the northeast is coded TS SE MOV NE.
3.1.5.13.14 Hailstone Size.
At designated stations, the hailstone size is coded in the following format: the hail identifier GR, followed by the size of the largest hailstone. The hailstone size is coded in ¼ in increments. For example, GR 1 3/4 would indicate that the largest hailstones were 1¾ in. in diameter. If small hail or snow pellets, GS, are coded in the body of the report, no hailstone size remark is required.
3.1.5.13.15 Virga.
At designated stations, Virga is coded in the following format: the identifier VIRGA, followed by the direction from the station. The direction of the phenomena from the station is optional, e.g., VIRGA or VIRGA SW.
3.1.5.13.16 Variable Ceiling Height.
The variable ceiling height is coded in the following format: the identifier CIG, followed by the lowest ceiling height recorded, V denoting variability between two values, and ending with the highest ceiling height. A single space follows the identifier with no other spaces between the letter V and the lowest/highest ceiling values. For example, CIG 005V010 would indicate a ceiling is variable between 500 ft and 1,000 ft.
3-23
3.1.5.13.17 Obscurations.
Obscurations, surface-based or aloft, are coded in the following format: the weather identifier causing the obscuration at the surface or aloft, followed by the sky cover of the obscuration aloft (FEW, SCT, BKN, OVC) or at the surface (FEW, SCT, BKN), and the height. Surface-based obscurations have a height of 000. A space separates the weather causing the obscuration and the sky cover; no space is between the sky cover and the height. For example, fog hiding 3/8 to 4/8 of the sky is coded FG SCT000; a broken layer at 2,000 ft composed of smoke is coded FU BKN020.
3.1.5.13.18 Variable Sky Condition.
Variable sky condition remarks are coded in the following format: the two operationally significant sky conditions (FEW, SCT, BKN, and OVC), separated by spaces, and V denoting the variability between the two ranges.
If several layers have the same condition amount, the layer height of the variable layer is coded. For example, a cloud layer at 1,400 ft varying between broken and overcast is coded BKN014 V OVC.
3.1.5.13.19 Significant Cloud Types.
At manual stations, significant cloud type remarks are coded in all reports.
3.1.5.13.20 Cumulonimbus.
Cumulonimbus not associated with thunderstorms is coded as CB, followed by the direction from the station, and the direction of movement, when known. The location, direction, and direction of movement entries are separated from each other by a space. For example, a CB up to 10 sm west of the station moving toward the east would be coded CB W MOV E. If the CB was more than 10 sm to the west, the remark is coded CB DSNT W.
Cumulonimbus (CB) always evolves from the further development of towering cumulus (TCU). The unusual occurrence of lightning and thunder within or from a CB leads to its popular title, thunderstorm. A thunderstorm usually contains severe or greater turbulence, severe icing, and Low-Level Wind Shear (LLWS).
3.1.5.13.21 Towering Cumulus.
Towering cumulus clouds are coded in the following format: the identifier TCU, followed by the direction from the station. The cloud type and direction entries are separated by a space. For example, a towering cumulus cloud up to 10 sm west of the station is coded TCU W.
3.1.5.13.22 Standing Lenticular or Rotor Clouds.
Stratocumulus (SCSL), altocumulus (ACSL), cirrocumulus (CCSL), or rotor clouds are coded in the following format: the cloud type followed by the direction from the station. The cloud type and direction entries are separated by a space. For example, altocumulus standing lenticular clouds observed southwest through west of the station are coded ACSL SW-W; an apparent
3-24 rotor cloud 5 to 10 sm northeast of the station is coded APRNT ROTOR CLD NE; and cirrocumulus clouds south of the station are coded CCSL S.
3.1.5.13.23 Ceiling Height at Second Location.
At designated stations, the ceiling height at a second location is coded in the following format: the identifier CIG, followed by the measured height of the ceiling and the specific location of the ceilometer(s) at the station. This remark is only generated when the ceiling is lower than that contained in the body of the report. For example, if the ceiling measured by a second sensor located at Runway 11 is broken at 200 ft, the remark would be coded CIG 002 RWY11.
3.1.5.13.24 Pressure Rising or Falling Rapidly.
At designated stations, the reported pressure is evaluated to determine if a pressure change is occurring. If the pressure is rising or falling at a rate of at least 0.06 in per hour and the pressure change totals 0.02 in or more at the time of the observation, a pressure change remark is reported. When the pressure is rising or falling rapidly at the time of observation, the remark pressure rising rapidly (PRESRR) or pressure falling rapidly (PRESFR) is included in the remarks.
3.1.5.13.25 Sea-Level Pressure.
At designated stations, the sea-level pressure is coded in the following format: the identifier SLP, immediately followed by the sea-level pressure in millibars (mb)1. The hundreds and thousands units are not coded and must be inferred. For example, a sea-level pressure of 998.2 mb is coded SLP982. A sea-level pressure of 1,013.2 mb would be coded SLP132. For a METAR, if sea-level pressure is not available, it is coded SLPNO.
3.1.5.13.26 Aircraft Mishap.
If a SPECI report is taken to document weather conditions when notified of an aircraft mishap, the remark ACFT MSHP is coded in the report, but the SPECI is not transmitted.
3.1.5.13.27 No SPECI Reports Taken (Plain Language).
At manual stations where SPECIs are not taken, the remark NOSPECI is coded to indicate no changes in weather conditions will be reported until the next METAR.
3.1.5.13.28 Snow Increasing Rapidly.
At designated stations, the snow increasing rapidly remark is reported in the next METAR whenever the snow depth increases by 1 in or more in the past hour. The remark is coded in the following format: the remark indicator
1 Although the international unit of pressure measurement is now the Pascal, we will use the term millibar in this document version because, at this time, it is felt the reader is probably more familiar with millibars. Increasingly in meteorology literature, however, the term hectopascal (hPa) has replaced the term millibar to conform to international standards and because 1 hPa = 1 mb.
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