Aviation Weather Services, Advisory Circular 00-45F, Revision 1 AC 00-45F (July 2008) Section 3: Observed Text Products Page 3-17 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; and
Insofar as possible, remarks are entered in the order they are presented in the following paragraphs (and Table 3-5).
3.1.3.13 Automated, Manual, and Plain Language Remarks These remarks generally elaborate on parameters reported in the body of the report.
Automated and manual remarks may be generated either by an automated station or observer.
Plain language remarks are only provided from an observer.
3.1.3.13.1 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 Any other pertinent data about the eruption
For example, a remark on a volcanic eruption would look like the following:
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.
3.1.3.13.2 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 that a tornado began at 13 minutes past the hour and was 6 statute miles northeast of the station.
3.1.3.13.3 Type of Automated Station AO1 or AO2 are 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.
3.1.3.13.4 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
Aviation Weather Services, Advisory Circular 00-45F, Revision 1 AC 00-45F (July 2008) Section 3: Observed Text Products Page 3-18 direction/speed group and the time. For example, a peak wind of 45 knots from 280 degrees which occurred at 15 minutes past the hour is coded PK WND 28045/15.
3.1.3.13.5 Wind Shift Wind shift is coded in the 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 as WSHFT 30 FROPA.
3.1.3.13.6 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 statute miles would be coded TWR VIS 1 1/2.
3.1.3.13.7 Variable Prevailing Visibility Variable prevailing visibility is coded in the following format: the remark identifier VIS, followed 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 1/2 and 2 statute miles would be coded VIS 1/2V2.
3.1.3.13.8 Sector Visibility (Plain Language) Sector visibility is coded in the following format: the remark identifier VIS, followed by the sector referenced to 8 points of the compass, and the sector visibility in statute miles. For example, a visibility of 2 1/2 statute miles in the northeastern octant is coded VIS NE 2 1/2.
3.1.3.13.9 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 2 1/2 statute miles measured by a second sensor located at runway 11 is coded VIS 2 1/2 RWY11.
3.1.3.13.10 Lightning When lightning is observed at a manual station, the frequency, type of lightning and location is reported. The contractions for the type and frequency of lightning are based on Table 3-6, for example, OCNL LTGICCG NW, FRQ LTG VC, or LTG DSNT W.
When lightning is detected by an automated system:
Within 5 nautical miles of the Airport Location Point (ALP), it is reported as TS in the body of the report with no remark;
Between 5 and 10 nautical miles of the ALP, it is reported as VCTS in the body of the report with no remark; and
Beyond 10 but less than 30 nautical miles of the ALP, it is reported in remarks only as LTG DSNT followed by the direction from the ALP.
Aviation Weather Services, Advisory Circular 00-45F, Revision 1 AC 00-45F (July 2008) Section 3: Observed Text Products Page 3-19
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.
3.1.3.13.11 Beginning and Ending of Precipitation At designated stations, the beginning and ending time of precipitation is 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 as RAB05E30SNB20E55. If the precipitation were showery, the remark is coded SHRAB05E30SHSNB20E55. If rain ended and snow began at 0042, the remark would be coded as RAESNB42.
3.1.3.13.12 Beginning and Ending of Thunderstorms The beginning and ending of thunderstorms are coded in the following format: TS for thunderstorms, 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.
3.1.3.13.13 Thunderstorm Location (Plain Language) Thunderstorm locations are coded in the following format: the thunderstorm identifier, TS, followed by 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.
3.1.3.13.14 Hailstone Size (Plain Language) 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 inch increments.
For example, GR 1 3/4 would indicate that the largest hailstone were 1 ¾ inches in diameter. If small hail or snow pellets, GS, is coded in the body of the report, no hailstone size remark is required.
Aviation Weather Services, Advisory Circular 00-45F, Revision 1 AC 00-45F (July 2008) Section 3: Observed Text Products Page 3-20
3.1.3.13.15 Virga (Plain Language) 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.
3.1.3.13.16 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 and 1,000 feet.
3.1.3.13.17 Obscurations (Plain Language) 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 feet composed of smoke is coded FU BKN020.
3.1.3.13.18 Variable Sky Condition (Plain Language) 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 feet varying between broken and overcast is coded BKN014 V OVC.
3.1.3.13.19 Significant Cloud Types (Plain Language) Significant cloud type remarks are coded in all reports.
3.1.3.13.19.1 Cumulonimbus or Cumulonimbus Mammatus Cumulonimbus or Cumulonimbus Mammatus not associated with thunderstorms are coded in the following format: the cloud type (CB or CBMAM) followed by the direction from the station and the direction of movement when known. The cloud type, location, direction, and direction of movement entries are separated from each other by a space. For example, a CB up to 10 statute miles west of the station moving toward the east would be coded CB W MOV E. If the CB was more than 10 statute miles 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, low level wind shear (LLWS), and instrument flight rules (IFR) conditions.
Aviation Weather Services, Advisory Circular 00-45F, Revision 1 AC 00-45F (July 2008) Section 3: Observed Text Products Page 3-21
Figure 3-5. Cumulonimbus (CB) Example CB always evolves from the further development of towering cumulus (TCU). The usual 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, low level wind shear (LLWS), and instrument flight rules (IFR) conditions. (Copyright Robert A. Prentice, 1990)
Figure 3-6. Cumulonimbus Mammatus (CBMAM) Example Cumulonimbus Mammatus (CBMAM) (also called mammatus) appears as hanging protuberances, like pouches, on the undersurface of a cloud. (Copyright Robert A. Prentice, 1993)
Aviation Weather Services, Advisory Circular 00-45F, Revision 1 AC 00-45F (July 2008) Section 3: Observed Text Products Page 3-22
3.1.3.13.19.2 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 statute miles west of the station is coded as TCU W.
Figure 3-7. Towering Cumulus (TCU) Example Towering Cumulus (TCU). TCU is produced by strong convective updrafts and, thus, indicates turbulence.
Icing is typically found above the freezing level. TCU often transforms into cumulonimbus (CB). (Copyright Charles A. Doswell, III, 1977)
Aviation Weather Services, Advisory Circular 00-45F, Revision 1 AC 00-45F (July 2008) Section 3: Observed Text Products Page 3-23
3.1.3.13.19.3 Altocumulus Castellanus Altocumulus Castellanus is coded in the following format: the identifier ACC followed by direction from the station. The cloud type and direction entries are separated by a space. For example, an altocumulus cloud 5 to 10 statute miles northwest of the station is coded ACC NW.
Figure 3-8. Altocumulus Castellanus (ACC) Example Altocumulus Castellanus (ACC). ACC indicates convective turbulence aloft from the top of the cloud to its base and usually an undetermined height below cloud base as well. (Photo courtesy of National Severe Storms Laboratory/University of Oklahoma)
Aviation Weather Services, Advisory Circular 00-45F, Revision 1 AC 00-45F (July 2008) Section 3: Observed Text Products Page 3-24
3.1.3.13.19.4 Standing Lenticular or Rotor Clouds Stratocumulus (SCSL), altocumulus (ACSL), or 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 rotor cloud 5 to 10 statute miles northeast of the station is coded APRNT ROTOR CLD NE; and cirrocumulus clouds south of the station are coded CCSL S.
Figure 3-9. Standing Lenticular and Rotor Clouds Example From top to bottom: Cirrocumulus standing lenticular (CCSL), altocumulus standing lenticular (ACSL), and rotor cloud. These clouds are characteristic of mountain waves. Mountain waves can occasionally produce violent downslope windstorms. Intense mountain waves can present a significant hazard to aviation by producing severe or even extreme turbulence that extends upward into the lower stratosphere.
3.1.3.13.20 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 feet, the remark would be CIG 002 RWY11.
Aviation Weather Services, Advisory Circular 00-45F, Revision 1 AC 00-45F (July 2008) Section 3: Observed Text Products Page 3-25
3.1.3.13.21 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 inch per hour and the pressure change totals 0.02 inch 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 PRESRR (pressure rising rapidly) or PRESFR (pressure falling rapidly) is included in the remarks.
3.1.3.13.22 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 hectopascals. The hundreds and thousands units are not coded and must be inferred. For example, a sea-level pressure of
998.2 hectopascals is coded as SLP982. A sea-level pressure of 1013.2 hectopascals would be coded as SLP132. For a METAR, if sea-level pressure is not available, it is coded as SLPNO.
3.1.3.13.23 Aircraft Mishap (Plain Language) 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 not transmitted.
3.1.3.13.24 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.
3.1.3.13.25 Snow Increasing Rapidly At designated stations, the snow increasing rapidly remark is reported, in the NEXT METAR, whenever the snow depth increases by 1 inch or more in the past hour. The remark is coded in the following format: the remark indicator 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 inches in the past hour with a total depth on the ground of 10 inches is coded SNINCR 2/10.
3.1.3.13.26 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.
3.1.3.14 Additive and Automated Maintenance Data Additive data groups (Table 3-5) are only reported at designated stations and are primarily used by the NWS for climatological purposes. Most have no direct impact on the aviation community but a few are discussed below.
3.1.3.14.1 Hourly Temperature and Dew Point At designated stations, the hourly temperature and dew point group are further coded to the tenth of a degree Celsius. For example, a recorded temperature of +2.6ºC and dew point of -1.5ºC would be coded as T00261015.
The format for the coding is as follows:
Aviation Weather Services, Advisory Circular 00-45F, Revision 1 AC 00-45F (July 2008) Section 3: Observed Text Products Page 3-26 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 10th 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 Dew Point disseminated to the nearest 10th and read as 01.5
No spaces are between the entries. For example, a temperature of 2.6ºC and dew point of –
1.5ºC is reported in the body of the report as 03/M01 and the hourly temperature and dew point group as T00261015. If the dew point is missing only the temperature is reported; if the temperature is missing the hourly temperature and dew point group is not reported.
3.1.3.14.2 Maintenance Data Groups The following maintenance data groups, Sensor Status Indicators and the Maintenance Indicator, are only reported from automated stations.
3.1.3.14.2.1 Sensor Status Indicators Sensor status indicators are reported as indicated below:
If the Runway Visual Range 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
3.1.3.14.2.2 Maintenance Indicator A maintenance indicator, $, is coded when an automated system detects maintenance is needed on the system.
3.1.4 Examples of METAR Reports, Explanations, and Phraseology
METAR KMKL 021250Z 33018KT 290V360 1/2SM R31/2600FT SN BLSN FG VV008 00/M03 A2991 RMK AO2 RAESNB42 SLPNO T00111032
Aviation Weather Services, Advisory Circular 00-45F, Revision 1 AC 00-45F (July 2008) Section 3: Observed Text Products Page 3-27 METAR Aviation Routine Weather Report KMKL United States Jackson McKellar-Sipes Regional Airport, Tennessee 021250Z The 2nd day of the month, 1300 hour scheduled report taken at 1250 UTC 33018KT Wind 330 degrees at 18 knots 290V360 Wind direction variable between 290 and 360 degrees 1/2SM Visibility one-half statute mile R31/2600FT Runway 31, runway visual range on runway 2,600 feet SN Moderate snow BLSN FG Blowing snow and fog VV008 Indefinite ceiling, vertical visibility 800 feet AGL 00/M03 Temperature 0°C, dew point -3°C A2991 Altimeter, 29.91 inches of mercury RMK Remarks AO2 Automated station with a precipitation discriminator RAESNB42 Rain ended at four two, snow began at four two past the hour SLPNO Sea-level pressure not available T00111032 Temperature 1.1°C, dew point -3.2°C
Jackson McKellar-Sipes Regional Airport, wind three three zero at one eight, wind variable between two niner zero and three six zero, visibility one-half, runway three one R-V-R, two thousand six hundred, snow, blowing snow, fog, indefinite ceiling eight hundred, temperature zero, dew point minus three, altimeter two niner niner one, remarks rain ended and snow began at four two past the hour.
METAR KIPT 191254Z 00000KT 1 1/2SM -RA BR SCT034 BKN100 19/18 A2993 RMK AO2 RAB24 SLP133 P0001 T01890178
METAR Aviation Routine Weather Report KIPT United States Williamsport Regional Airport, Pennsylvania 191254Z 19th day of the month, the 1300 hour scheduled report taken 1254 UTC 00000KT Wind calm 1 1/2SM Visibility one and one-half statute mile -RA BR Light rain, mist SCT034 BKN100 Scattered 3,400 feet AGL, ceiling broken 10,000 feet AGL 19/18 Temperature 19 degrees Celsius, Dew Point 18 degrees Celsius A2993 Altimeter, 29.93 inches of mercury RMK Remarks AO2 Automated station with a precipitation discriminator RAB24 Rain began at 1224 UTC SLP133 Sea level pressure 1013.3 hectopascals P0001 Precipitation over the past hour 00.01 inch T01890178 Temperature 18.9 degrees Celsius, dew point 17.8 degrees Celsius
Williamsport Regional Airport, wind calm, visibility one and one half, light rain, mist, three thousand four hundred scattered, ceiling one zero thousand broken, temperature one niner, dew point one eight, altimeter two niner niner three, remarks rain began at two four past the hour.
Aviation Weather Services, Advisory Circular 00-45F, Revision 1 AC 00-45F (July 2008) Section 3: Observed Text Products Page 3-28 SPECI KCVG 312228Z 28024G36KT 3/4SM +TSRA SQ BKN008 OVC020CB 28/23 A3000 RMK TSB24 TS OHD MOV E
SPECI Aviation Selected Special Weather Report KCVG United States Covington Cincinnati/Northern Kentucky International Airport, Kentucky 312228Z The 31st of the month Special report taken at 2228 UTC 28024G36KT Wind 280 degrees at 24 knots, gusts 36 knots 3/4SM Visibility three-quarters statute mile +TSRA SQ Thunderstorm with heavy rain and squalls BKN008 OVC020CB Ceiling broken 800 feet AGL, overcast 2,000 feet AGL cumulonimbus 28/23 Temperature 28°C, dew point 23°C A3000 Altimeter 30.00 inches of mercury RMK Remarks TSB24 Thunderstorm began at two four minutes past the hour TS OHD MOV E Thunderstorm overhead moving east
Covington Cincinnati/Northern Kentucky International Airport, special report, two eight observation, wind two eight zero at two four, gusts three six, visibility three-quarters, thunderstorm, heavy rain, squall, ceiling eight hundred broken, two thousand overcast cumulonimbus, temperature two eight, dew point two three, altimeter three zero zero zero, thunderstorm began two four, thunderstorm overhead, moving east.”
METAR KLAX 191350Z 08004KT 4SM HZ OVC009 18/16 A2997 RMK AO2 SLP147 T01830156
METAR Aviation Routine Weather Report KLAX United States Los Angeles International Airport, California 191350Z The 19th day of the month, the 1400 hour scheduled report at 1350 UTC 08004KT Wind 80 degrees at 4 knots 4SM Visibility 4 statute miles HZ Haze OVC009 Ceiling overcast 900 feet AGL 18/16 Temperature 18 C, dew point 16 C A2997 Altimeter 29.97 inches of mercury RMK Remarks AO2 Automated observation with precipitation discriminator SLP147 Sea level pressure 1014.7 hectopascals T01830156 Temperature 18.3oC, dew point 15.6oC
Los Angeles International Airport, wind zero eight zero at four, visibility four, haze, ceiling niner hundred overcast, temperature one eight, dew point one six, altimeter two niner niner seven.
SPECI KDEN 241310Z 09014G35KT 1/4SM +SN FG VV002 01/01 A2975 RMK AO2 TWR VIS 1/2 RAESNB08
SPECI Aviation Selected Special Weather Report KDEN United States Denver International Airport, Colorado