11/14/16 Aviation Weather Services AC 00-45H 3-9 touchdown RVR is reported. RVR may be reported for up to four designated runways in other countries.
When the RVR varies by more than one reportable value, the lowest and highest values will be shown with V between them, indicating variable conditions. For example, the 10-minute RVR for Runway 01L varying between 600 ft and 1,000 ft would be coded R01L/0600V1000FT.
If RVR is less than its lowest reportable value, the visual range group is preceded by M. For example, an RVR for Runway 01L of less than 600 ft is coded R01L/M0600FT.
If RVR is greater than its highest reportable value, the visual range group is preceded by a P. For example, an RVR for Runway 27 of greater than 6,000 ft will be coded R27/P6000FT.
3.1.5.8 Present Weather Group.
METAR KOKC 011955Z AUTO 22015G25KT 180V250 3/4SM R17L/2600FT +TSRA BR OVC010CB 18/16 A2992 RMK AO2 TSB25 TS OHD MOV E SLP132 Present weather includes precipitation, obscurations, and other weather phenomena. The appropriate notations found in Table 3-2, METAR/SPECI Notations for Reporting Present Weather, are used to code present weather.
11/14/16 Aviation Weather Services AC 00-45H 3-10 Table 3-2. METAR/SPECI Notations for Reporting Present Weather1
QUALIFIER WEATHER PHENOMENA
INTENSITY OR
PROXIMITY
DESCRIPTOR
PRECIPITATION
OBSCURATION
OTHER 1 2 3 4 5
- Light MI Shallow DZ Drizzle BR Mist PO Dust/Sand Whirls
+ Moderate2 Heavy PR BC Partial Patches RA SN Rain Snow FG FU Fog Smoke SQ FC Squalls
Funnel Cloud, Tornado or Waterspout4 VC
In the Vicinity3 DR BL Low Drifting Blowing SG IC Snow Grains Ice Crystals (Diamond Dust) VA DU Volcanic Ash Widespread Dust
SS DS Sandstorm
Duststorm SH TS FZ
Shower(s) Thunderstorms Freezing PL GR GS UP Ice Pellets
Hail
Small Hail and/or Snow Pellets Unknown Precipitation
SA HZ PY
Sand
Haze Spray
1. The weather groups are constructed by considering columns 1 through 5 in the table above in sequence, i.e., intensity followed by description, followed by weather phenomena, e.g., heavy rain shower(s) is coded as +SHRA.
2. To denote moderate intensity no entry or symbol is used.
3. See text for vicinity definitions.
4. Tornadoes and waterspouts are coded as +FC.
Separate groups are used for each type of present weather. Each group is separated from the other by a space. METAR/SPECI reports contain no more than three present weather groups.
11/14/16 Aviation Weather Services AC 00-45H 3-11 When more than one type of present weather is reported at the same time, present weather is reported in the following order:
• Tornadic activity (tornado, funnel cloud, or waterspout).
• Thunderstorm(s) (with and without associated precipitation).
• Present weather in order of decreasing dominance (i.e., the most dominant type reported first).
• Left-to-right in Table 3-2 (columns 1 through 5).
Qualifiers may be used in various combinations to describe weather phenomena. Present weather qualifiers fall into two categories: intensity (see paragraph 3.1.5.8.1) or proximity (see paragraph 3.1.5.8.2) and descriptors (see paragraph 3.1.5.8.3).
3.1.5.8.1 Intensity Qualifier.
The intensity qualifiers are light, moderate, and heavy. They are coded with precipitation types, except ice crystals (IC) and hail (GR or GS), including those associated with a thunderstorm (TS) and those of a showery nature (SH). Tornadoes and waterspouts are coded as heavy (+FC). No intensity is ascribed to the obscurations of blowing dust (BLDU), blowing sand (BLSA), and blowing snow (BLSN). Only moderate or heavy intensity is ascribed to sandstorm (SS) and duststorm (DS).
When more than one form of precipitation is occurring at a time, or precipitation is occurring with an obscuration, the reported intensities are not cumulative. The reported intensity will not be greater than the intensity for each form of precipitation. For example, -FZRAPL is light freezing rain and light ice pellets, not light freezing rain and moderate ice pellets.
3.1.5.8.2 Proximity Qualifier.
Weather phenomena occurring beyond the point of observation (between 5 and 10 sm) are coded as in the vicinity (VC). VC can be coded in combination with thunderstorm (TS), fog (FG), shower(s) (SH), well-developed dust/sand whirls (PO), blowing dust (BLDU), blowing sand (BLSA), blowing snow (BLSN), sandstorm (SS), and duststorm (DS).
Intensity qualifiers are not coded in conjunction with VC.
For example, VCFG can be decoded as meaning some form of fog is between 5 and 10 sm of the point of observation. If VCSH is coded, showers are occurring between 5 and 10 sm of the point of observation.
Weather phenomena occurring at the point of observation (at the station) or in the vicinity of the point of observation are coded in the body of the report.
Weather phenomena observed beyond 10 sm from the point of observation (at the station) is not coded in the body, but may be coded in the remarks section (see paragraph 3.1.5.12).
11/14/16 Aviation Weather Services AC 00-45H 3-12
3.1.5.8.3 Descriptor Qualifier.
Descriptors are qualifiers that further amplify weather phenomena and are used in conjunction with some types of precipitation and obscurations. The descriptor qualifiers are: shallow (MI), partial (PR), patches (BC), low drifting (DR), blowing (BL), shower(s) (SH), thunderstorm (TS), and freezing (FZ).
Only one descriptor is coded for each weather phenomena group
(e.g., FZDZ).
The descriptors shallow (MI), partial (PR), and patches (BC) are only coded with fog (FG) (e.g., MIFG). Mist (BR) is not coded with any descriptor.
The descriptors low drifting (DR) and blowing (BL) will only be coded with dust (DU), sand (SA), and snow (SN) (e.g., BLSN or DRSN). DR is coded with DU, SA, or SN for raised particles drifting less than 6 ft above the ground.
When blowing snow is observed with snow falling from clouds, both phenomena are reported (e.g., SN BLSN). If blowing snow is occurring and the observer cannot determine whether or not snow is also falling, then BLSN is reported. Spray (PY) is coded only with blowing (BL).
The descriptor for showery-type precipitation (SH) is coded only with one or more of the precipitation qualifiers for rain (RA), snow (SN), ice pellets (PL), small hail (GS), or large hail (GR). When any type of precipitation is coded with VC, the intensity and type of precipitation is not coded.
The descriptor for thunderstorm (TS) may be coded by itself when the thunderstorm is without associated precipitation. A thunderstorm may also be coded with the precipitation types of rain (RA), snow (SN), ice pellets (PL), small hail and/or snow pellets (GS), or hail (GR). For example, a thunderstorm with snow and small hail and/or snow pellets would be coded as TSSNGS. TS is not coded with SH.
The descriptor freezing (FZ) is only coded in combination with fog (FG), drizzle (DZ), or rain (RA) (e.g., FZRA). FZ is not coded with SH.
3.1.5.8.4 Precipitation.
Precipitation is any form of water particle, whether liquid or solid, that falls from the atmosphere and reaches the ground. The precipitation types are:
drizzle (DZ), rain (RA), snow (SN), snow grains (SG), ice crystals (IC), ice pellets (PL), hail (GR), small hail and/or snow pellets (GS), and unknown precipitation (UP). UP is reported if an automated station detects the occurrence of precipitation, but the precipitation sensor cannot recognize the type.
11/14/16 Aviation Weather Services AC 00-45H 3-13 Up to three types of precipitation may be coded in a single present weather group. They are coded in order of decreasing dominance based on intensity.
3.1.5.8.5 Obscuration.
Obscurations are any phenomenon in the atmosphere, other than precipitation, that reduces the horizontal visibility in the atmosphere. The obscuration types are: mist (BR), fog (FG), smoke (FU), volcanic ash (VC), widespread dust (DU), sand (SA), haze (HZ), and spray (PY). Spray (PY) is coded only as BLPY.
With the exception of volcanic ash, low drifting dust, low drifting sand, low drifting snow, shallow fog, partial fog, and patches (of) fog, an obscuration is coded in the body of the report if the surface visibility is less than 7 miles (mi), or considered operationally significant. Volcanic ash is always reported when observed.
3.1.5.8.6 Other Weather Phenomena.
Other weather phenomena types include: well-developed dust/sand whirls (PO), sandstorms (SS), duststorms (DS), squalls (SQ), funnel clouds (FC), and tornados and waterspouts (+FC).
Examples:
-DZ Light drizzle -RASN Light rain and (light) snow SN BR (Moderate) snow, mist -FZRA FG Light freezing rain, fog SHRA (Moderate) rain shower VCBLSA Blowing sand in the vicinity -RASN FG HZ Light rain and (light) snow, fog, haze TS Thunderstorm (without precipitation) +TSRA Thunderstorm, heavy rain +FC TSRAGR BR Tornado, thunderstorm, (moderate) rain, hail, mist
3.1.5.9 Sky Condition Group.
METAR KOKC 011955Z AUTO 22015G25KT 180V250 3/4SM R17L/2600FT +TSRA BR OVC010CB 18/16 A2992 RMK AO2 TSB25 TS OHD MOV E SLP132 Sky condition is a description of the appearance of the sky. It includes either cloud cover, vertical visibility, or clear skies.
11/14/16 Aviation Weather Services AC 00-45H 3-14 The sky condition group is based on the amount of cloud cover (the first three letters) followed by the height of the base of the cloud cover (final three digits). No space is between the amount of cloud cover and the height of the layer. The height of the layer is recorded in feet above ground level (AGL).
Sky condition is coded in ascending order and ends at the first overcast layer.
At mountain stations, if the layer is below station level, the height of the layer will be coded as ///.
Vertical visibility is coded as VV, followed by the vertical visibility into the indefinite ceiling. An indefinite ceiling is a ceiling classification applied when the reported ceiling value represents the vertical visibility upward into surface-based obscuration. No space is between the group identifier and the vertical visibility. Figure 3-3, Obscuration Effects on Slant Range Visibility, illustrates the effect of an obscuration on the vision from a descending aircraft.
Figure 3-3. Obscuration Effects on Slant Range Visibility
The ceiling is 500 ft in both examples, but the indefinite ceiling example (bottom) produces a more adverse impact to landing aircraft. This is because an obscuration (e.g., fog, blowing dust, snow) limits runway acquisition due to reduced slant range visibility. This pilot would be able to see the ground, but not the runway. If the pilot was at approach minimums, the approach could not be continued and a missed approach must be executed.
11/14/16 Aviation Weather Services AC 00-45H 3-15 Clear skies are coded in the format SKC or CLR. When SKC is used, an observer indicates no layers are present; CLR is used by automated stations to indicate no layers are detected at or below 12,000 ft.
Each coded layer is separated from the others by a space. Each layer reported is coded by using the appropriate reportable contraction seen in Table 3-3, METAR/SPECI Contractions for Sky Cover. A report of clear skies (SKC or CLR) is a complete layer report within itself. The abbreviations FEW, SCT, BKN, and OVC will be followed (without a space) by the height of the layer.
Table 3-3. METAR/SPECI Contractions for Sky Cover Reportable Contraction Meaning Summation Amount of Layer VV Vertical Visibility 8/8 SKC or CLR1 Clear 0 FEW2 Few 1/8 – 2/8 SCT Scattered 3/8 – 4/8 BKN Broken 5/8 – 7/8 OVC Overcast 8/8
1. The abbreviation CLR will be used at automated stations when no layers at or below 12,000 ft are reported; the abbreviation SKC will be used at manual stations when no layers are reported.
2. Any layer amount less than 1/8 is reported as FEW.
The height is coded in hundreds of feet above the surface using three digits in accordance with Table 3-4, METAR/SPECI Increments of Reportable Values of Sky Cover Height.
Table 3-4. METAR/SPECI Increments of Reportable Values of Sky Cover Height Range of Height Values (feet) Reportable Increment (feet) Less than or equal to 5,000 To nearest 100 5,001 to 10,000 To nearest 500 Greater than 10,000 To nearest 1,000 The ceiling is the lowest layer aloft reported as broken or overcast. If the sky is totally obscured with ground-based clouds, the vertical visibility is the ceiling.
11/14/16 Aviation Weather Services AC 00-45H 3-16 Figure 3-4. METAR/SPECI Sky Condition Coding
Clouds at 1,200 ft obscure 2/8ths of the sky (FEW). Higher clouds at 3,000 ft obscure an additional 1/8th of the sky, and because the observer cannot see above the 1,200-f t layer, he is to assume that the higher 3,000-ft layer also exists above the lower layer (SCT). The highest clouds at 5,000 ft obscure 2/8ths of the sky, and again since the observer cannot see past the 1,200 and 3,000-f t layers, he is to assume the higher 5,000-ft layer also exists above the lower layers (BKN). The sky condition group would be coded as: FEW012 SCT030 BKN050.
At manual stations, cumulonimbus (CB) or towering cumulus (TCU) is appended to the associated layer. For example, a scattered layer of towering cumulus at 1,500 ft would be coded SCT015TCU, and would be followed by a space if there were additional higher layers to code.
Examples:
SKC No layers are present CLR No layers are detected at or below 12,000 ft AGL FEW004 Few at 400 ft AGL SCT023TCU Scattered layer of towering cumulus at 2,300 ft BKN100 Broken layer (ceiling) at 10,000 ft OVC250 Overcast layer (ceiling) at 25,000 ft VV001 Indefinite ceiling with a vertical visibility of 100 ft FEW012 SCT046 Few clouds at 1,200 ft, scattered layer at 4,600 ft
11/14/16 Aviation Weather Services AC 00-45H 3-17 SCT033 BKN085 Scattered layer at 3,300 ft, broken layer (ceiling) at 8,500 ft SCT018 OVC032CB Scattered layer at 1,800 ft, overcast layer (ceiling) of cumulonimbus at 3,200 ft SCT009 SCT024 BKN048 Scattered layer at 900 ft, scattered layer at 2,400 ft, broken layer (ceiling) at 4,800 ft
3.1.5.10 Temperature/Dewpoint Group.
METAR KOKC 011955Z AUTO 22015G25KT 180V250 3/4SM R17L/2600FT +TSRA BR OVC010CB 18/16 A2992 RMK AO2 TSB25 TS OHD MOV E SLP132 Temperature is the degree of hotness or coldness of the ambient air, as measured by a suitable instrument. Dewpoint is the temperature to which a given parcel of air must be cooled at constant pressure and constant water vapor content for the air to become fully saturated.
Temperature and dewpoint are coded as two digits rounded to the nearest whole degree Celsius. For example, a temperature of 0.3 ºC would be coded at
00. Sub-zero temperatures and dewpoints are prefixed with an M. For example, a temperature of 4 ºC with a dewpoint of –2 ºC would be coded as 04/M02; a temperature of –2 ºC would be coded as M02.
If temperature is not available, the entire temperature/dewpoint group is not coded. If dewpoint is not available, temperature is coded followed by a solidus (/) and no entry is made for dewpoint. For example, a temperature of 1.5 ºC and a missing dewpoint would be coded as 02/.
3.1.5.11 Altimeter.
METAR KOKC 011955Z AUTO 22015G25KT 180V250 3/4SM R17L/2600FT +TSRA BR OVC010CB 18/16 A2992 RMK AO2 TSB25 TS OHD MOV E SLP132 The altimeter setting group codes the current pressure at elevation. This setting is then used by aircraft altimeters to determine the true altitude above a fixed plane of mean sea level (MSL).
The altimeter group always starts with an A and is followed by the four-digit group representing the pressure in tens, units, tenths, and hundredths of inches (in) of mercury. The decimal point is not coded. For example, an altimeter setting of 29.92 in of Mercury would be coded as A2992.
3.1.5.12 Remarks (RMK).
METAR KOKC 011955Z AUTO 22015G25KT 180V250 3/4SM R17L/2600FT +TSRA BR OVC010CB 18/16 A2992 RMK AO2 TSB25 TS OHD MOV E SLP132
11/14/16 Aviation Weather Services AC 00-45H 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 Additive and Automated Maintenance Data
1. Volcanic Eruptions
14. Hailstone Size 27. Precipitation amount within a specified time period*
2. Funnel Cloud 15. Virga 28. Cloud Types*
3. Type of Automated Station 16. Variable Ceiling Height 29. Duration of Sunshine*
4. Peak Wind 17. Obscurations 30. Hourly Temperature and Dewpoint
5. Wind Shift 18. Variable Sky Condition 31. 6-Hourly Maximum Temperature*
6. Tower or Surface Visibility 19. Significant Cloud Types 32. 6-Hourly Minimum Temperature*
7. Variable Prevailing Visibility 20. Ceiling Height at Second Location 33. 24-Hour Maximum and Minimum Temperature*
8. Sector Visibility 21. Pressure Rising or Falling Rapidly 34. 3-Hourly Pressure Tendency*
9. Visibility at Second Location 22. Sea-Level Pressure 35. Sensor Status Indicators
10. Lightning 23. Aircraft Mishap 36. Maintenance Indicator
11. Beginning and Ending of Precipitation 24. No SPECI Reports Taken 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.
12. Beginning and Ending of Thunderstorms 25. Snow Increasing Rapidly
13. Thunderstorm Location 26. Other Significant Information 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.
11/14/16 Aviation Weather Services AC 00-45H 3-19
• Distance remarks are in statute miles except for automated lightning remarks, which are in nautical miles.
• 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.
• Insofar 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
11/14/16 Aviation Weather Services AC 00-45H 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 1 ½ 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