Aviation Weather Services, Advisory Circular 00-45F, Change 2 (March 2009)
3.1.3 Format
Figure 3-1. METAR/SPECI Coding Format
A METAR/SPECI (Figure 3-1) has two major sections: the Body (consisting of a maximum of 11 groups) and the Remarks (consisting of 2 categories). Together, the body and remarks make up the complete METAR/SPECI. When an element does not occur, or cannot be observed, the corresponding group is omitted from that particular report.
3.1.3.1 Type of Report
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 type of report, METAR or SPECI precedes the body of all reports.
3.1.3.2 Station Identifier
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 station identifier, in ICAO format, is included in all reports to identify the station to which the coded report applies.
The ICAO airport code is a four-letter alphanumeric code designating each airport around the world. The ICAO codes are used for flight planning by air traffic controllers and airline operation departments. These codes are not the same as the International Air Transport Association (IATA) codes encountered by the general public used for reservations, baggage handling and in airline timetables. ICAO codes are also used to identify weather stations located on- or offairport.
AC 00-45F, CHG 2 Section 3: Observed Text Products Page 3-3
Aviation Weather Services, Advisory Circular 00-45F, Change 2 (March 2009) Unlike the IATA codes, the ICAO codes have a regional structure. For example, the first letter is allocated by continent (Figure 3-2), the second is a country within the continent; the remaining two are used to identify each airport.
Figure 3-2. ICAO Continent codes
In the contiguous U. S., ICAO station identifiers are coded K followed by the three-letter IATA identifier. For example, the Seattle, Washington (IATA identifier SEA) becomes the ICAO identifier KSEA.
ICAO station identifiers in Alaska, Hawaii, and Guam begin with the continent code P, followed by the proper country code (A, H, and G respectively), and the two-letter airport identifier.
Examples:
PANC Anchorage, AK PAOM Nome, AK PHNL Honolulu, HI PHKO Keahole Point, HI PGUM Agana, Guam PGUA Anderson AFB, Guam
Canadian station identifiers begin with C, followed by the country code, and the two-letter airport identifier.
Examples:
AC 00-45F, CHG 2 Section 3: Observed Text Products Page 3-4
Aviation Weather Services, Advisory Circular 00-45F, Change 2 (March 2009) CYYZ Toronto, Canada CYYC Calgary Canada CYQB Quebec, Canada CYXU London, Canada CZUM Churchill Falls, Canada
Mexican and western Caribbean station identifiers begin with M, followed by the proper country code and two-letter airport identifier.
Examples:
MMMX Mexico City, Mexico MUGM Guantanamo Bay, Cuba MDSD Santo Domingo, Dominican Republic MYNN Nassau, Bahamas
Eastern Caribbean station identifiers begin with T, followed by the proper country code, and airport identifier.
Examples:
TJSJ San Juan, Puerto Rico TIST Saint Thomas, Virgin Islands
For a list of Alaskan, Hawaiian, Canadian, Mexican, Pacific, and Caribbean ICAO identifiers see FAA Order 7350.7. For a complete worldwide listing, see ICAO Document 7910, “Location Indicators.” Both are available on-line.
3.1.3.3 Date and Time of Report
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 date and time is coded in all reports as follows: the day of the month is the first two digits
(01) followed by the hour (19), and the minutes (55). The coded time of observations is the actual time of the report or when the criteria for a SPECI is met or noted. If the report is a correction to a previously disseminated report, the time of the corrected report is the same time used in the report being corrected. The date and time group always ends with a Z indicating Zulu time (or UTC). For example, METAR KOKC 011955Z would be disseminated as the 2000 hour scheduled report for station KOKC taken on the 1st of the month at 1955 UTC.
3.1.3.4 Report Modifier (As Required)
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 report modifier, AUTO, identifies the METAR/SPECI as a fully automated report with no human intervention or oversight. In the event of a corrected METAR or SPECI, the report modifier, COR, is substituted for AUTO.
AC 00-45F, CHG 2 Section 3: Observed Text Products Page 3-5
Aviation Weather Services, Advisory Circular 00-45F, Change 2 (March 2009)
3.1.3.5 Wind 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
Wind is the horizontal motion of air past a given point. It is measured in terms of velocity, which is a vector that includes direction and speed. It indicates the direction the wind is coming FROM.
In the wind group, the wind direction is coded as the first three digits (220) and is determined by averaging the recorded wind direction over a 2-minute period. It is coded in tens of degrees relative to true north using three figures. Directions less than 100 degrees are preceded with a
0. For example, a wind direction of 900 is coded as 090.
Immediately following the wind direction is the wind speed coded in two or three digits (15).
Wind speed is determined by averaging the speed over a 2-minute period and is coded in whole knots using the units, tens digits and, when required, the hundreds digit. When wind speeds are less than 10 knots, a leading zero is used to maintain at least a two digit wind code. For example, a wind speed of 8 knots will be coded 08KT. The wind group is always coded with a KT to indicate wind speeds are reported in knots. Other countries may use kilometers per hour (KPH) or meters per second (MPS) instead of knots.
Examples:
05008KT Wind 50 degrees at 8 knots 15014KT Wind 150 degrees at 14 knots 340112KT Wind 340 degrees at 112 knots
3.1.3.5.1 Wind Gust Wind speed data for the most recent 10 minutes is examined to evaluate the occurrence of gusts. Gusts are defined as rapid fluctuations in wind speed with a variation of 10 knots or more between peaks and lulls. The coded speed of the gust is the maximum instantaneous wind speed.
Wind gusts are coded in two or three digits immediately following the wind speed. Wind gusts are coded in whole knots using the units, tens, and, if required, the hundreds digit. For example, a wind out of the west at 20 knots with gusts to 35 knots would be coded 27020G35KT.
3.1.3.5.2 Variable Wind Direction (speed 6 knots or less) Wind direction may be considered variable when, during the previous 2-minute evaluation period, the wind speed was 6 knots or less. In this case, the wind may be coded as VRB in place of the 3-digit wind direction. For example, if the wind speed was recorded as 3 knots, it would be coded VRB03KT.
3.1.3.5.3 Variable Wind Direction (speed greater than 6 knots) Wind direction may also be considered variable when, during the 2-minute evaluation period, it varies by 60 degrees or more and the speed is greater than 6 knots. In this case a variable wind direction group immediately follows the wind group. The directional variability is coded in a clockwise direction and consists of the extremes of the wind directions separated by a V. For AC 00-45F, CHG 2 Section 3: Observed Text Products Page 3-6
Aviation Weather Services, Advisory Circular 00-45F, Change 2 (March 2009) example, if the wind is variable from 180º to 240º at 10 knots, it would be coded 21010KT 180V240.
3.1.3.5.4 Calm Wind When no motion of air is detected, the wind is reported as calm. A calm wind is coded as 00000KT.
3.1.3.6 Visibility 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
Visibility is a measure of the opacity of the atmosphere.
Prevailing visibility is the reported visibility considered representative of recorded visibility conditions at the station during the time of observation. It is the greatest distance that can be seen throughout at least half of the horizon circle, not necessarily continuous.
Surface visibility is the prevailing visibility from the surface at manual stations or the visibility derived from sensors at automated stations.
The visibility group is coded as the surface visibility in statute miles. A space is coded between whole numbers and fractions of reportable visibility values. The visibility group ends with SM to indicate that the visibility is in statute miles. For example, a visibility of one and a half statute miles is coded 1 1/2SM. Other countries may use meters (no code).
Automated stations use an M to indicate “less than.” For example, M1/4SM means a visibility of less than one-quarter statute mile.
3.1.3.7 Runway Visual Range (RVR) 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
The runway visual range (RVR) is an instrument-derived value representing the horizontal distance a pilot may see down the runway.
RVR is reported whenever the station has RVR equipment and prevailing visibility is 1 statute mile or less and/or the RVR for the designated instrument runway is 6,000 feet or less.
Otherwise the RVR group is omitted.
Runway visual range is coded in the following format: the initial R is code for runway and is followed by the runway number. When more than one runway is defined with the same runway number a directional letter is coded on the end of the runway number. Next is a solidus /;
followed by the visual range in feet and then FT completes the RVR report. For example, an RVR value for Runway 01L of 800 feet would be coded R01L/0800FT. Other countries may use meters.
RVR values are coded in increments of 100 feet up to 1,000 feet, increments of 200 feet from 1,000 feet to 3,000 feet, and increments of 500 feet from 3,000 feet to 6,000 feet. Manual RVR AC 00-45F, CHG 2 Section 3: Observed Text Products Page 3-7
Aviation Weather Services, Advisory Circular 00-45F, Change 2 (March 2009) is not reported below 600 feet. At automated stations, RVR may be reported for up to four designated runways.
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 and 1,000 feet 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 feet 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 feet will be coded R27/P6000FT.
3.1.3.8 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 are used to code present weather.
AC 00-45F, CHG 2 Section 3: Observed Text Products Page 3-8
Aviation Weather Services, Advisory Circular 00-45F, Change 2 (March 2009)
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 PR Partial RA Rain FG Fog SQ Squalls
+ Heavy BC Patches SN Snow FU Smoke FC Funnel Cloud, Tornado, or Waterspout4
VC In the Vicinity3 DR Low Drifting SG Snow Grains VA Volcanic Ash SS Sandstorm BL Blowing IC Ice Crystals (Diamond Dust)
DU Widespread Dust DS Duststorm SH Shower(s) PL Ice Pellets SA Sand
TS Thunderstorms GR Hail HZ Haze
FZ Freezing GS Small Hail and/or Snow Pellets
PY Spray UP Unknown Precipitation
1. The weather groups are construct ed by considering columns 1 to 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.
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 is reported first.
• Left-to-right in Table 3-2 (Columns 1 through 5).
AC 00-45F, CHG 2 Section 3: Observed Text Products Page 3-9
Aviation Weather Services, Advisory Circular 00-45F, Change 2 (March 2009) Qualifiers may be used in various combinations to describe weather phenomena. Present weather qualifiers fall into two categories: intensity (Section 3.1.3.8.1) or proximity (Section
3.1.3.8.2) and descriptors (Section 3.1.3.8.3).
3.1.3.8.1 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.
3.1.3.8.2 Proximity Qualifier Weather phenomena occurring beyond the point of observation (between 5 and 10 statute miles) 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 statute miles of the point of observation. If VCSH is coded, showers are occurring between 5 and 10 statute miles 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 10SM from the point of observation (at the station) is not coded in the body but may be coded in the remarks section (Section 3.1.3.12).
3.1.3.8.3 Descriptor Qualifier Descriptors are qualifiers which 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 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 six feet 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).
AC 00-45F, CHG 2 Section 3: Observed Text Products Page 3-10
Aviation Weather Services, Advisory Circular 00-45F, Change 2 (March 2009) 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). The SH descriptor indicates showery-type precipitation. 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 are 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.
3.1.3.8.4 Precipitation Precipitation is any of the forms of water particles, 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 (IP), 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.
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.
3.1.3.8.5 Obscuration Obscurations are any phenomenon in the atmosphere, other than precipitation, reducing the horizontal visibility. 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 or considered operationally significant. Volcanic ash is always reported when observed.
3.1.3.8.6 Other Weather Phenomena Other weather phenomena types include: well-developed dust/sand whirls (PO), sand storms (SS), dust storms (DS), squalls (SQ), funnel clouds (FC), and tornados and waterspouts (+FC).
Examples:
-DZ L i g h t drizzle -RASN Light rain and 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 snow, fog, haze TS Thunderstorm (without precipitation) AC 00-45F, CHG 2 Section 3: Observed Text Products Page 3-11
Aviation Weather Services, Advisory Circular 00-45F, Change 2 (March 2009) +TSRA Thunderstorm, heavy rain +FC TSRAGR BR Tornado, thunderstorm, (moderate) rain, hail, mist
3.1.3.9 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 is coded as: sky condition, vertical visibility, or clear skies.
The sky condition group is based on the amount of sky cover (the first three letters) followed by the height of the base of the sky cover (final three digits). No space is between the amount of sky 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. No space is between the group identifier and the vertical visibility. Figure 3-3 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 feet 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, etc.) limits runway AC 00-45F, CHG 2 Section 3: Observed Text Products Page 3-12
Aviation Weather Services, Advisory Circular 00-45F, Change 2 (March 2009) 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.
Clear skies are coded in the format, SKC or CLR. When SKC is used, an observer indicates no layers are present; and CLR is used by automated stations to indicate no layers are detected at or below 12,000 feet.
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. 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 feet 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.
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.
AC 00-45F, CHG 2 Section 3: Observed Text Products Page 3-13
Aviation Weather Services, Advisory Circular 00-45F, Change 2 (March 2009)
Figure 3-4. METAR/SPECI Sky Condition Coding Clouds at 1,200 feet obscure 2/8ths of the sky (FEW). Higher clouds at 3,000 feet obscure an additional 1/8th of the sky, and because the observer cannot see above the 1,200-foot layer, he is to assume that the higher 3,000-foot layer also exists above the lower layer (SCT). The highest clouds at 5,000 feet obscure 2/8ths of the sky, and again since the observer cannot see past the 1,200 and 3,000-foot layers, he is to assume the higher 5,000-foot 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 feet 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 feet AGL FEW004 Few at 400 feet AGL SCT023TCU Scattered layer of towering cumulus at 2,300 feet BKN105 Broken layer ( ceiling) at 10,500 feet OVC250 Overcast layer ( ceiling) at 25,000 feet VV001 Indefinite ceiling with a vertical visibility of 100 feet FEW012 SCT046 Few clouds at 1,200 feet, scattered layer at 4,600 feet SCT033 BKN085 Scattered layer at 3,300 feet, broken layer ( ceiling) at 8,500 feet SCT018 OVC032CB Scattered layer at 1,800 feet, overcast layer ( ceiling) of cumulonimbus at 7,500 feet SCT009 SCT024 BKN048 Scattered layer at 900 feet, scattered layer at 2,400 feet, broken layer (ceiling) at 4,800 feet
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