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Section 3 | Observed Text Products

3.1 Aviation Routine Weather Reports (METAR) and Aviation Selected Special Weather Reports (SPECI)

Surface weather observations are fundamental to all meteorological services. Observations are the basic information upon which forecasts and warnings are made in support of a wide range of weather sensitive activities within the public and private sectors, including aviation.

Although the METAR/SPECI code is used worldwide, each country is allowed to make modifications or exceptions to the code for use in their particular country. This section will focus on the U.S. modifications and exceptions. METAR/SPECIs are available online at: http://adds.aviationweather.gov/metars/

3.1.1 Aviation Routine Weather Report (METAR)

Aviation Routine Weather Report (METAR) is the primary observation code used in the U. S. to satisfy World Meteorological Organization (WMO) and International Civil Aviation Organization (ICAO) requirements for reporting surface meteorological data. A METAR report includes the airport identifier, time of observation, wind, visibility, runway visual range, present weather phenomena, sky conditions, temperature, dew point, and altimeter setting. Excluding the airport identifier and the time of observation, this information is collectively referred to as “the body of the report.” As an addition, coded and/or plain language information elaborating on data in “the body of the report” may be appended to the end of the METAR in a section coded as “Remarks.” The contents of the “Remarks” section vary with the type of reporting station. The METAR may be abridged at some designated stations only including a few of the mentioned elements.

3.1.2 Aviation Selected Special Weather Report (SPECI)

An Aviation Selected Special Weather Report (SPECI) is an unscheduled report taken when any of the criteria given in Table 3-1 are observed during the interim period between the hourly reports. SPECI contains all data elements found in a METAR plus additional plain language information which elaborates on data in the body of the report. All SPECIs are made as soon as possible after the relevant criteria are observed.

Whenever SPECI criteria are met at the time of the routine METAR, a METAR is issued.

Table 3-1. SPECI Criteria

1

Wind Shift

Wind direction changes by 45 degrees or more in less than 15 minutes and the wind speed is 10 knots or more throughout the wind shift.

2

Visibility

Surface visibility as reported in the body of the report decreases to less than, or if below, increases to equal or exceed:

a. 3 miles

b. 2 miles

c. 1 mile

d. The lowest standard instrument approach procedure minimum as published in the National Ocean Service (NOS) U.S Instrument Procedures. If none published use ½ mile.

3

Runway Visual Range (RVR)

The highest value from the designated RVR runway decreases to less than, or if below, increases to equal or exceed 2,400 feet during the preceding 10 minutes. U.S. military stations may not report a SPECI based on RVR.

4

Tornado, Funnel Cloud, or Waterspout

a. is observed.

b. disappears from sight, or ends.

5

Thunderstorm

a. begins (a SPECI is not required to report the beginning of a new thunderstorm if one is currently reported).

b. ends.

6

Precipitation

a. hail begins or ends.

b. freezing precipitation begins, ends, or changes intensity.

c. ice pellets begin, end, or change intensity

7

Squalls

When they occur

8

Ceiling

The ceiling (rounded off to reportable values) forms or dissipates below, decreases to less than, or if below, increases to equal or exceed:

a. 3,000 feet.

b. 1,500 feet

c. 1,000 feet

d. 500 feet

e. The lowest standard instrument approach procedure minimum as published in the National Ocean Service (NOS) U.S Instrument Procedures. If none published, use 200 feet.

9

Sky Condition

A layer of clouds or obscurations aloft is present below 1,000 feet and no layer aloft was reported below 1,000 feet in the preceding METAR or SPECI.

10

Volcanic Eruption

When an eruption is first noted

11

Aircraft Mishap

Upon notification of an aircraft mishap, unless there has been an intervening observation

12

Miscellaneous

Any other meteorological situation designated by the responsible agency of which, in the opinion of the observer, is critical.

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 off-airport.

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:

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.

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

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

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.

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 constructed 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).

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).

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 Light 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)

+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 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.

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 3,200 feet

SCT009 SCT024 BKN048 Scattered layer at 900 feet, scattered layer at 2,400 feet, broken layer (ceiling) at 4,800 feet

3.1.3.10 Temperature/Dew Point 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 seems as measured by a suitable instrument. Dew point 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 dew point are coded as two digits rounded to the nearest whole degree Celsius. For example, a temperature of 0.3ºC would be coded at 00. Sub-zero temperatures and dew points are prefixed with an M. For example, a temperature of 4ºC with a dew point of –2ºC would be coded as 04/M02; a temperature of –2ºC would be coded as M02.

If temperature is not available, the entire temperature/dew point group is not coded. If dew point is not available, temperature is coded followed by a solidus, /, and no entry made for dew point. For example, a temperature of 1.5ºC and a missing dew point would be coded as 02/.

3.1.3.11 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.

The altimeter group always starts with an A (the international indicator for altimeter in inches of mercury) and is followed by the four digit group representing the pressure in tens, units, tenths, and hundredths of inches of mercury. The decimal point is not coded. For example, an altimeter setting of 29.92 inches of Mercury would be coded as A2992.

3.1.3.12 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

Remarks are included in all 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 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*

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 Dew Point

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, i.e., direction from the station, if known. Weather phenomena beyond 10 statute miles 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 statute miles east of the station would be coded as VCSH E; lightning 25 statute miles west of the station would be coded as LTG DSNT W;
  • 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; 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

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.

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.

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.

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)

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)

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)

3.1.3.13.19.4 Standing Lenticular or Rotor Clouds

Cirrocumulus (CCSL), altocumulus (ACSL), stratocumulus (SCSL), 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.

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:

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 METAR/SPECI Examples

METAR PAHL 031836Z AUTO 07009KT 10SM CLR 13/02 A2980 RMK AO1 PNO

GROUP

CODED

TRANSLATION

Type of Report

METAR

Aviation Routine Weather Report

Station Identifier

PAHL

United States Huslia, Alaska

Date and Time of Report

031836Z

3rd day of the month, 1836 UTC

Report Modifier

AUTO

automated observation with no human augmentation

Wind

07009KT

Wind from 070 degrees (the east) at 9 knots (10 mph, 4.6 m/s)

Visibility

10SM

Visibility ten statute miles (16 kilometers)

Runway Visual Range

[omitted]

Present Weather

[omitted]

There may or may not be significant weather present at this time

Sky Condition

CLR

Sky clear below 12,000 feet AGL

Temperature/Dewpoint

13/02

Temperature 13°C (55°F), dewpoint 2°C (36°F)

Altimeter

A2980

29.80 inches of mercury (1009.2 millibars, 1009.2 hectopascals)

Remarks

RMK

Remarks section designator

Automated, Manual, and Plain Language

A01

Automated station without a precipitation discriminator

Additive and Automated Maintenance Data

PNO

Tipping bucket rain gauge not operating

METAR KNSI 031656Z VRB03KT 5SM HZ SCT007 21/17 A2989 RMK SLP121 T02060172

GROUP

CODED

TRANSLATION

Type of Report

METAR

Aviation Routine Weather Report

Station Identifier

KNSI

United States San Nicolas Island, California

Date and Time of Report

031656Z

3rd day of the month, 1656 UTC

Report Modifier

[omitted]

Either a manual or an augmented observation

Wind

VRB03KT

Wind variable at 3 knots (4 mph, 1.5 m/s)

Visibility

5SM

Visibility five statute miles (8.0 kilometers)

Runway Visual Range

[omitted]

Present Weather

HZ

Haze

Sky Condition

SCT007

Scattered at 700 feet AGL

Temperature/Dewpoint

21/17

Temperature 21°C (69°F), dewpoint 17°C (63°F)

Altimeter

A2989

29.89 inches of mercury (1012.3 millibars, 1012.3 hectopascals)

Remarks

RMK

Remarks section designator

Automated, Manual, and Plain Language

SLP121

Sea level pressure 1012.1 hectopascals (1012.1 millibars)

Additive and Automated Maintenance Data

T02060172

Temperature 20.6°C (69°F), dewpoint 17.2°C (63°F)

SPECI KCOT 292020Z AUTO 13009KT 3SM TSRA BR SCT011 BKN028 OVC043 23/21 A2991 RMK AO2 PK WND 13029/2000 LTG DSNT ALQDS P0020

GROUP

CODED

TRANSLATION

Type of Report

SPECI

Aviation Selected Special Weather Report

Station Identifier

KCOT

United States Cotulla, Texas

Date and Time of Report

292020Z

29th day of the month, 2020 UTC

Report Modifier

AUTO

Automated observation with no human augmentation

Wind

13009KT

Wind from 130 degrees (the southeast) at 9 knots (10 mph, 4.7 m/s)

Visibility

3SM

Visibility three statute miles (5 kilometers)

Runway Visual Range

[omitted]

Present Weather

TSRA BR

Thunderstorm, moderate rain, mist

Sky Condition

SCT011 BKN028 OVC043

Scattered at 11,000 feet AGL, Ceiling broken at 2,800 feet AGL, Overcast at 4,300 feet AGL

Temperature/Dewpoint

23/21

Temperature 23°C (73°F), dewpoint 21°C (70°F)

Altimeter

A2991

29.91 inches of mercury (1013.0 millibars, 1013.0 hectopascals)

Remarks

RMK

Remarks section designator

Automated, Manual, and Plain Language

AO2

Automated station with a precipitation discriminator

PK WND 13029/2000

Peak wind from 130 degrees (the southeast) at 29 knots (33 mph, 14.9 m/s) occurred at 2000 UTC

LTG DSNT ALQDS

Lightning distant all quadrants

Additive and Automated Maintenance Data

P0020

0.20 inches of precipitation fell in the past hour

METAR KMDW 090153Z 23003KT 1/2SM R31C/4000V4500FT SN FZFG VV002 M04/M05 A3004 RMK AO2 SLP191 SNINCR 1/10 P0000 T10391050

GROUP

CODED

TRANSLATION

Type of Report

METAR

Aviation Routine Weather Report

Station Identifier

KMDW

United States Chicago (Midway), Illinois

Date and Time of Report

090153Z

9th day of the month,0153 UTC

Report Modifier

[omitted]

Either a manual or an augmented observation

Wind

23003KT

Wind from 230 degrees (the southwest) at 3 knots (3 mph,1.6 m/s)

Visibility

1/2SM

Visibility one-half statute miles (0.8 kilometers)

Runway Visual Range

R31C/4000V4500FT

Runway 31 center visual range variable between 4,000 and 4,5000 feet

Present Weather

SN FZFG

Snow, freezing fog

Sky Condition

VV002

Indefinite ceiling, vertical visibility 200 feet

Temperature/Dewpoint

M04/M05

Temperature -4°C (25°F), dewpoint -5°C (23°F)

Altimeter

A3004

Altimeter 30.04 inches of mercury (1017.4 hectopascals, 1017.4 millibars)

Remarks

RMK

Remarks section designator

Automated, Manual, and Plain Language

A02

Automated station with a precipitation discriminator

SLP191

Sea level pressure 1019.1 hectopascals (1019.1 millibars)

SNINCR 1/10

Snow increasing rapidly, snow depth increase of 1 inch in the past hour, a total depth on the ground of 10 inches

Additive and Automated Maintenance Data

P0000

Less than 1/100 of an inch of precipitation fell in the past hour

T10391050

Temperature -3.9°C (25°F), dewpoint -5.0°C (23°F)

SPECI KMEM 091826 27013G27KT 240V310 1/2SM R36L/1000VP6000FT +TSRAGR FG FEW002 BKN023 OVC032CB 18/17 A2992 RMK A02 PK WND 31031/1802 WSHFT 1759 TSB22RAB17GRB23 PRESRR FRQ LTGIC W-NW TS W-NW GR 1/2 P0005

GROUP

CODED

TRANSLATION

Type of Report

SPECI

Aviation Selected Special Weather Report

Station Identifier

KMEM

United States Memphis, Tennessee

Date and Time of Report

091826Z

9th day of the month, 1826 UTC

Report Modifier

[omitted]

Either a manual or an augmented observation

Wind

27013G27KT 240V310

Wind from 270 degrees (the west) at 13 knots (15 mph, 6.7 m/s) gusting to 27 knots (31 mph, 13.9 m/s), wind variable between 240 degrees (the west-southwest) and 310 degrees (the northwest)

Visibility

1/2SM

Visibility one-half statute miles (0.8 kilometers)

Runway Visual Range

R36L/1000VP6000FT

Runway 36 left visual range variable between 1,000 and more than 6,000 feet

Present Weather

+TSRAGR FG

Thunderstorm, heavy rain, hail, fog

Sky Condition

FEW002 BKN023 OVC032CB

Few at 200 feet AGL, ceiling broken at 2,300 feet AGL, overcast at 3,200 feet AGL cumulonimbus

Temperature/Dewpoint

18/17

Temperature 18°C (64°F), dewpoint 17°C (63°F)

Altimeter

A2992

29.92 inches of mercury (1013.2 millibars, 1013.2 hectopascals)

Remarks

RMK

Remarks section designator

Automated, Manual, and Plain Language

AO2

Automated station with a precipitation discriminator

PK WND 31031/1802

Peak wind from 310 degrees (the northwest) at 31 knots (36 mph, 15.9 m/s) occurred at 1802 or 2 minutes past the hour UTC

WSHFT 1759

Wind shift occurred at 1759 UTC

TSB22RAB17GRB23

Thunderstorm began at 22 minutes past the hour, rain began at 17 minutes past the hour, hail began at 23 minutes past the hour

PRESRR

Pressure rising rapidly

FRQ LTGIC W-NW

Frequent lightning in-cloud west through northwest

TS W-NW

Thunderstorm west through northwest

GR1/2

Largest hailstone 1/2 inches in diameter

Additive and Automated Maintenance Data

P0005

0.05 inches of precipitation fell in the past hour

SPECI KMSN 012312Z 13021G26KT 1SM -FZRAPL BR OVC011 00/M02 A2988 RMK AO2 PK WND 14031/2255 SFC VIS 1 1/2 P0005 $

GROUP

CODED

TRANSLATION

Type of Report

SPECI

Aviation Selected Special Weather Report

Station Identifier

KMSN

United States Madison, Wisconsin

Date and Time of Report

012312Z

1st day of the month, 2312 UTC

Report Modifier

[omitted]

Either a manual or an augmented observation

Wind

13021G26KT

Wind from 130 degrees (the southeast) at 21 knots (24 mph, 10.8 m/s) gusting to 26 knots (30 mph, 13.4 m/s)

Visibility

1SM

Visibility one statute mile (1.6 kilometers)

Runway Visual Range

[omitted]

Present Weather

-FZRAPL BR

Light freezing rain, ice pellets, mist

Sky Condition

OVC011

Ceiling overcast at 1,100 feet AGL

Temperature/Dewpoint

00/M02

Temperature 0°C (32°F), dewpoint -2°C (28°F)

Altimeter

A2988

29.88 inches of mercury (1011.9 millibars, 1011.9 hectopascals)

Remarks

RMK

Remarks section designator

Automated, Manual, and Plain Language

AO2

Automated station with a precipitation discriminator

PK WND 14031/2255

Peak wind from 140 degrees (the southeast) at 31 knots (36 mph, 15.9 m/s) occurred at 2255 UTC

SFC VIS 1 1/2

Surface visibility one and on-half statute mile

Additive and Automated Maintenance Data

P0005

0.05 inches of precipitation fell in the past hour

$

Maintenance is needed on the system

3.2 Pilot Weather Reports (PIREP)

No report is timelier than the one made from the flight deck of aircraft in flight. In fact, aircraft in flight are the only means of observing actual icing and turbulence conditions. Pilots welcome pilot weather reports (PIREPs) as well as pilot weather briefers and forecasters. 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 this inaccuracy. This will help the NWS verify forecast products and create more accurate products for the aviation community. Pilots should help themselves, the aviation public, and the aviation weather forecasters by providing PIREPs.

Pipe Up with a PIREP and help the aviation community operate more safely and effectively.

PIREPs are available in the internet at the Aviation Digital Data Service (ADDS) web page at: http://adds.aviationweather.gov/pireps/

3.2.1 Format

A PIREP is transmitted in a prescribed format (Figure 3-10). Required elements for all PIREPs are: message type, location, time, altitude/flight level, type aircraft, and at least one other element to describe the reported phenomena. The other elements will be omitted when no data is reported with them. All altitude references are mean sea level (MSL) unless otherwise noted. Distance for visibility is in statute miles and all other distances are in nautical miles. Time is reported in Universal Time Coordinated (UTC).

Figure 3-10. Pilot Weather Report (PIREP) Coding Format

3.2.1.1 Message 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)
  • Severe icing
  • Hail
  • Low Level Wind Shear (LLWS) within 2,000 feet of the surface. LLWS PIREPS are classified as UUA if the pilot reports air speed fluctuations of 10 knots or more or if air speed fluctuations are not reported but LLWS is reported, the PIREP is classified as UUA.
  • Volcanic ash clouds
  • Any other weather phenomena reported which 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 Section 3.2.1.1.1.

3.2.1.2 Location (/OV)

The Location (/OV) can be referenced either by geographical position or by route segment.

3.2.1.2.1 Location

Location can be referenced to a VHF NAVAID or an airport, using either the three-letter International Air Transport Association (IATA) or four letter International Civil Aviation Organization (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 VOR

/OV KJFK Over John F. Kennedy International Airport, New York City, NY

/OV APE230010 230 degrees at 10 nautical miles from the Appleton VOR

/OV KJFK107080 107 degrees at 80 nautical miles from John F. Kennedy International Airport, New York City, New York

3.2.1.2.1.1 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, Missouri to Charles B. Wheeler Downtown Airport, Kansas City, Missouri

/OV KSTL090030-KMKC045015 From 90 degrees at 30 nautical miles from Lambert-Saint Louis International Airport, Missouri to 45 degrees at 15 nautical miles from Charles B. Wheeler Downtown Airport, Kansas City, Missouri

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

3.2.1.4 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 feet 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 feet MSL, top 6,500 feet MSL

/SK OVC100-TOP110/ SKC Base of an overcast layer 10,000 feet MSL, top 11,000 feet MSL, clear above

/SK OVC015-TOP035/OVC230 Base of an overcast layer 1,500 feet MSL, top 3,500 feet MSL, base of an overcast layer 23,000 feet MSL

/SK OVC-TOP085 Overcast layer, top 8,500 feet MSL

Cloud cover amount ranges are entered with a hyphen separating the amounts; i.e., BKN-OVC.

Examples:

/SK SCT-BKN050-TOP100 Base of a scattered to broken layer 5,000 feet MSL, top 10,000 feet MSL

/SK BKN-OVCUNKN-TOP060/BKN120-TOP150/ SKC Base of a broken to overcast layer unknown, top 6,000 feet MSL, base of a broken layer 12,000 feet MSL, top 15,000 feet MSL, clear above

Unknown heights are indicated by the contraction UNKN.

Example:

/SK OVC065-TOPUNKN Base of an overcast layer 6,500 feet MSL, top unknown

If a pilot indicates he/she is in the clouds, IMC is entered.

Example:

/SK OVC065-TOPUNKN /RM IMC Base of an overcast layer 6,500 feet MSL, top unknown, remark, in the clouds

When more than one layer is reported, layers are separated by a solidus (/).

3.2.1.7 Flight Visibility and Weather (/WX)

Weather conditions encountered by the pilot are reported as follows:

Flight visibility, when reported, is entered first in the /WX field. It is coded as FV followed by a two-digit visibility value rounded down, if necessary, to the nearest whole statute mile and appended with SM (FV03SM). If visibility is reported as unrestricted, FV99SM is entered.

Flight weather types are entered using one or more of the standard surface weather reporting symbols contained in Table 3-7.

Table 3-7. PIREP Weather Type and Symbols

Type

METAR Code

Drifting / Blowing Snow

DRSN/BLSN

Drifting Dust

DRDU

Drifting Sand

DRSA

Drizzle/Freezing Drizzle

DZ/FZDZ

Dust / Blowing Dust

DU/BLDU

Duststorm

DS

Fog (visibility less than 5/8SM)

FG

Freezing Fog

FZFG

Freezing Rain

FZRA

Funnel Cloud

FC

Hail (Approximately ¼-inch diameter or more)

GR

Hail Shower

SHGR

Haze

HZ

Ice Crystals

IC

Ice Pellets/Showers

PL/SHPL

Mist (visibility great than or equal to 5/8SM)

BR

Patchy Fog

BCFG

Patchy Fog on part of airport

PRFG

Rain/Showers

RA/SHRA

Sand/Blowing Sand

SA/BLSA

Sandstorms

SS

Shallow Fog

MIFG

Small Hail/Snow Pellet Showers

SHGS

Small Hail/Snow Pellets

GS

Smoke

FU

Snow Grains

SG

Snow / Showers

SN/SHSN

Spray

PY

Squalls

SQ

Thunderstorm

TS

Tornado/Waterspout

+FC

Unknown Precipitation

UP

Volcanic Ash

VA

Well developed Dust/Sand Whirls

PO

Intensity modifiers for precipitation (- for light, no qualifier for moderate, and + for heavy) indicates precipitation type, except ice crystals and hail, including those associated with a thunderstorm and those of a showery nature.

Intensity modifiers for obscurations are ascribed as moderate or heavy (+) for dust and sandstorms only. No intensity modifiers are used for blowing dust, blowing sand, or blowing snow.

Example:

/WX FV01SM +DS000-TOP083/SKC /RM DURC Flight visibility 1 statute mile, base heavy duststorm layer at the surface, top 8,300 feet MSL, clear above, remarks, during climb

When more than one form of precipitation is combined in the report, the dominant type is reported first.

Examples:

/WX FV00SM +TSRAGR Flight visibility zero statute miles, thunderstorm, heavy rain, hail

/WX FV02SM BRHZ000-TOP083 Flight visibility 2 statute miles, base of a haze and mist layer at the surface, top 8,300 feet MSL

If a funnel cloud is reported, it is coded as FC following /WX group and is spelled out as Funnel Cloud after /RM group. If a tornado or waterspout is reported, it is coded +FC following /WX group and TORNADO or WATERSPOUT is spelled out after the /RM group.

Examples:

/WX FC /RM FUNNEL CLOUD Funnel cloud, remarks, funnel cloud

/WX +FC /RM TORNADO Tornado, remark, tornado

When the size of hail is stated, it is coded in 1/4-inch increments in remarks (/RM) group.

The proximity qualifier VC (vicinity) is only used with TS, FG, FC, +FC, SH, PO, BLDU, BLSA, and BLSN.

Example:

/WX FV02SM BLDU000-TOP083 VC W Flight visibility 2 statute miles, base of a blowing dust layer at the surface, top 8,300 feet MSL in the vicinity, west

When more than one type of weather is reported, they are reported in the following order:

  • TORNADO, WATERSPOUT, or FUNNEL CLOUD
  • Thunderstorm with or without associated precipitation
  • Weather phenomena in order of decreasing predominance.

No more than three groups are used in a single PIREP.

Weather layers are entered with the base and/or top of the layer when reported. The same format as in the sky condition (/SK) group is used.

Example:

/WX FU002-TOP030 Base of a smoke layer, 200 feet MSL, top 3,000 feet MSL

3.2.1.8 Air Temperature (/TA)

Outside air temperature (/TA) is reported using two digits in degrees Celsius. Negative temperatures is prefixed with an M; e.g., /TA 08 or /TA M08.

3.2.1.9 Wind Direction and Speed (/WV)

Wind direction and speed is encoded using three digits to indicate wind direction (magnetic) and two or three digits to indicate reported wind speed. When the reported speed is less than 10 knots, a leading zero is used. The wind group will always have KT appended to represent the units in knots.

Examples:

/WV 02009KT Wind 20 degrees (magnetic) at 9 knots

/WV 28057KT Wind 280 degrees (magnetic) at 57 knots

/WV 350102KT Wind 350 degrees (magnetic) at 102 knots

3.2.1.10 Turbulence (/TB)

Turbulence intensity, type, and altitude are reported after wind direction and speed.

Duration (INTMT, OCNL, or CONS) is coded first (if reported by the pilot)) followed by intensity (LGT, MOD, SEV, or EXTRM). Range or variation of intensity is separated with a hyphen; e.g., MOD-SEV. If turbulence was forecasted, but not encountered, NEG is entered.

Type is coded second. CAT (Clear Air Turbulence) or CHOP is entered if reported by the pilot. High-level turbulence (normally above 15,000 feet AGL) not associated with clouds (including thunderstorms) is reported as CAT.

Altitude is reported (last) only if it differs from value reported in the Altitude/Flight Level (/FL) group. When a layer of turbulence is reported, height values are separated with a hyphen. If lower or upper limits are not defined, BLO or ABV is used.

Examples:

/TB LGT Light turbulence

/TB LGT 040 Light turbulence at 4,000 feet MSL

/TB OCNL MOD-SEV BLO 080 Occasional moderate to severe turbulence below 8,000 feet MSL

/TB MOD-SEV CAT 350 Moderate to severe clear air turbulence at 35,000 feet MSL

/TB NEG 120-180 Negative turbulence between 12,000 to 18,000 feet MSL

/TB CONS MOD CHOP 220/NEG 230-280 Continuous moderate chop at 22,000 feet MSL, negative turbulence between 23,000 to 28,000 feet MSL

/TB MOD CAT ABV 290 Moderate clear air turbulence above 29,000 feet MSL

Turbulence reports should include location, altitude, or range of altitudes, and aircraft type, and, when reported, whether in clouds or clear air. The pilot determines the degree of turbulence, intensity, and duration (occasional, intermittent, and continuous). The report should be obtained and disseminated, when possible, in conformance with the U.S. Standard Turbulence Criteria Table 3-8.

Table 3-8. PIREP Turbulence Reporting Criteria

Intensity

Aircraft Reaction

Reaction Inside Aircraft

Reporting Term-Definition

Light

Turbulence that momentarily causes slight, erratic changes in altitude and/or attitude (pitch, roll, yaw). Report as Light Turbulence;1

or

Turbulence that causes slight, rapid and somewhat rhythmic bumpiness without appreciable changes in altitude or attitude. Report as Light Chop.

Occupants may feel a slight strain against belts or shoulder straps. Unsecured objects may be displaced slightly. Food service may be conducted and little or no difficulty is encountered in walking.

Occasional – Less than 1/3 of the time.

Intermittent-1/3 to 2/3

Continuous-More than 2/3

Moderate

Turbulence that is similar to Light Turbulence but of greater intensity. Changes in altitude and/or attitude occur but the aircraft remains in positive control at all times. It usually causes variations in indicated airspeed. Report as Moderate Turbulence;1

or

Turbulence that is similar to Light Chop but of greater intensity. It causes rapid bumps or jolts without appreciable changes in aircraft or attitude. Report as Moderate Chop.1

Occupants feel definite strains against seat belts or shoulder straps. Unsecured objects are dislodged. Food service and walking are difficult.

NOTE

1. Pilots should report location(s), time (UTC), intensity, weather in or near clouds, altitude, type of aircraft and, when applicable, duration of turbulence.

2. Duration may be based on time between two locations or over a single location. All locations should be readily identifiable.

EXAMPLES:

Over Omaha. 1232Z, Moderate Turbulence, in cloud, flight Level 310, B737.

b. From 50 miles south of Albuquerque to 30 miles north of Phoenix, 1210Z to 1250Z, occasional Moderate Chop, Flight Level 330, DC8.

Severe

Turbulence that causes large, abrupt changes in altitude and/or attitude. It usually causes large variations in indicated airspeed. Aircraft may be momentarily out of control. Report as Severe Turbulence.1

Occupants are forced violently against seat belts or shoulder straps. Unsecured objects are tossed about. Food service and walking are impossible.

Extreme

Turbulence in which the aircraft is violently tossed about and is practically impossible to control. It may cause structural damage. Report as Extreme Turbulence.1

1 High level turbulence (normally above 15,000 feet ASL) not associated with clouds, including thunderstorms, should be reported as CAT (clear air turbulence) preceded by the appropriate intensity, or light or moderate chop.

3.2.1.11 Icing (/IC)

Icing intensity, type and altitude is reported after turbulence.

Intensity is coded first using contractions TRACE, LGT (light), MOD (moderate), or SEV severe). Reports of a range or variation of intensity is separated with a hyphen. If icing was forecast but not encountered, NEG (negative) is coded.

The following table classifies icing intensity according to its operational effects on aircraft.

Table 3-9. Icing Intensities, Contractions, and Airframe Ice Accumulation

Intensity

Contraction

Airframe Ice Accumulation

Trace

TRACE

Ice becomes perceptible. Rate of accumulation slightly greater than rate of sublimation. It is not hazardous even without the use of deicing/anti-icing equipment unless encountered for an extended period of time (over 1 hour).

Light

LGT

The rate of accumulation may create a problem if flight is prolonged in this environment (over 1 hour). Occasional use of deicing/anti-icing equipment removes/prevents accumulation. It does not present a problem if the deicing/anti-icing equipment is used.

Moderate

MOD

The rate of accumulation is such that even short encounters become potentially hazardous and use of deicing/anti-icing equipment or diversion is necessary.

Severe

SEV

The rate of accumulation is such that deicing/anti-icing equipment fails to reduce or control the hazard. Immediate diversion is necessary.

Icing type is reported second. Reportable types are RIME, CLR (clear), or MX (mixed).

The following table classifies icing type according to it description.

Table 3-10. Icing Types, Contractions, and Descriptions

Icing Type

Contraction

Description

Rime

RM

Rough, milky, opaque ice formed by the instantaneous freezing of small super-cooled water droplets.

Clear

CLR

A glossy, clear or translucent ice formed by the relatively slow freezing of large super-cooled water droplets.

Mixed

MX

A combination of both rime and clear.

The reported icing/altitude is coded (last) only if different from the value reported in the altitude/flight level (/FL) group. A hyphen is used to separate reported layers of icing. ABV (above) or BLO (below) is coded when a layer is not defined.

Pilot reports of icing should also include location (/OV), type aircraft (/TP), and air temperature (/TA).

Examples:

/IC LGT-MOD MX 085 Light to moderate mixed icing, 8,500 feet MSL

/IC LGT RIME Light rime icing

/IC MOD RIME BLO 095 Moderate rime icing below 9,500 feet MSL

/IC SEV CLR 035-062 Severe clear icing 3,500 to 6,200 feet MSL

3.2.1.12 Remarks (/RM)

The remarks (/RM) group is used to report a phenomenon which is considered important but does not fit in any of the other groups. This includes, but is not limited to, low-level wind shear

(LLWS) reports, thunderstorm lines, coverage and movement, size of hail (1/4-inch increments), lightning, clouds observed but not encountered, geographical or local description of where the phenomenon occurred, and contrails. Hazardous weather is reported first. LLWS is described to the extent possible.

3.2.1.12.1 Wind Shear

Ten knots or more fluctuations in wind speed (+/- 10KTS), within 2,000 feet of the surface, require an Urgent (UUA) pilot report. When Low Level Wind Shear is entered in a pilot report, LLWS is entered as the first remark in the remarks (/RM) group.

Example:

/RM LLWS +/-15 KT SFC-008 DURC RY22 JFK Remarks, Low Level Wind Shear, air speed fluctuations of plus or minus 15 knots, surface to 800 feet during climb, runway 22, John F. Kennedy International Airport, New York.

3.2.1.12.2 FUNNEL CLOUD, TORNADO, and WATERSPOUT

Funnel cloud, tornado, and waterspout are entered with the direction of movement when reported.

Example:

/RM TORNADO W MOV E Remarks, tornado west moving east

3.2.1.12.3 Thunderstorm

Thunderstorm coverage is coded as ISOL (isolated), FEW (few), SCT (scattered), NMRS (numerous) followed by description as LN (line), BKN LN (broken line), SLD LN (solid line) when reported. This is followed with TS, the location and movement, and the type of lightning when reported.

Example:

/RM NMRS TS S MOV E GR1/2 Remarks, numerous thunderstorms south moving east, hail 1/2–inch in diameter

3.2.1.12.4 Lightning

Lightning frequency is coded as OCNL (occasional) or FRQ (frequent), followed by type as LTGIC (lightning in cloud), LTGCC (lightning cloud to cloud), LTGCG (lightning cloud to ground), LTGCA (lightning cloud to air), or combinations, when reported.

Example:

/RM OCNL LTGICCG Remarks, occasional lighting in cloud, cloud to ground

3.2.1.12.5 Electrical Discharge

For an electrical discharge, DISCHARGE is coded followed by the altitude.

Example:

/RM DISCHARGE 120 Remarks, discharge, 12,000 feet MSL

3.2.1.12.6 Clouds

Remarks are used when clouds can be seen but were not encountered and reported in the sky condition group (/SK)

Examples:

/RM CB E MOV N Remarks, cumulonimbus east moving north

/RM OVC BLO Remarks, overcast below

3.2.1.12.7 Plain Language

If specific phraseology is not adequate, plain language is used to describe the phenomena or local geographic locations. Remarks that do not fit in other groups like DURC (during climb), DURD (during descent), RCA (reach cruising altitude), TOP, TOC (top of climb), or CONTRAILS are included.

Examples:

/RM BUMPY VERY ROUGH RIDE

/RM CONTRAILS

/UA/OV BIS270030/TM 1445/FL060/TP CVLT/TB LGT /RM DONNER SUMMIT PASS

3.2.1.12.8 Volcanic Eruptions

Volcanic ash alone is an Urgent PIREP. A report of volcanic activity includes as much information as possible including the name of the mountain, ash cloud and movement, height of the top and bottom of the ash, etc., is included. If the report is received from a source other than a pilot, Aircraft UNKN, Flight Level UNKN, and /RM UNOFFICIAL is entered.

Example:

/UUA/OV ANC240075/TM 2110/FL370/TP DC10/WX VA/RM VOLCANIC ERUPTION 2008Z MT AUGUSTINE ASH 40S MOV SSE

Urgent Pilot Weather Report, 240 degrees at 75 nautical miles from Anchorage International Airport, Alaska, 2110 UTC, flight level 370, a DC10 reported volcanic ash, remarks, volcanic eruption occurred at 2008 UTC Mount Augustine, ash 40 nautical miles south moving south-southeast.

3.2.1.12.9 SKYSPOTTER

The SKYSPOTTER program is a result of a recommendation from the Safer Skies FAA/INDUSTRY Joint Safety Analysis and Implementation Teams. The term SKYSPOTTER indicates a pilot has received specialized training in observing and reporting in-flight weather phenomenon, pilot weather reports, or PIREPs.

When a PIREP is received from a pilot identifying themselves as a SKYSPOTTER aircraft, the additional comment “/AWC” is added at the end of the remarks section of the PIREP.

Example:

PIREP TEXT/RM REMARKS/AWC

3.2.2 PIREP Examples

UUA /OV ORD/TM 1235/FLUNKN/TP B727/TB MOD/RM LLWS +/- 20KT BLW 003 DURD RWY27L

Urgent Pilot Weather Report, over Chicago O’Hare Airport, Illinois, 1235 UTC, flight level unknown, from a Boeing 727, moderate turbulence, remarks, Low Level Wind Shear, airspeed fluctuations of plus or minus 20 knots below 300 feet AGL during descent, runway 27 left.

UUA /OV BAM260045/TM 2225/FL180/TP BE20/TB SEV/RM BROKE ALL THE BOTTLES IN THE BAR

Urgent Pilot Weather Report, 260 degrees at 45 nautical miles from Hazen VOR, Nevada, 2225 UTC, 18,000 feet MSL, Beech Super King Air 200, severe turbulence, remarks, broke all the bottles in the bar.

UA /OV KMRB-KPIT/TM 1600/FL100/TP BE55/SK BKN024-TOP032/BKN-OVC043-TOPUNKN /TA M12/IC LGT-MOD RIME 055-080

Pilot Weather Report, Martinsburg, West Virginia to Pittsburgh International Airport, Pennsylvania, 1600 UTC, 10,000 feet MSL, Beechcraft Baron, base of a broken layer 2,400 feet MSL, top 3,200 feet MSL, base of a broken to overcast layer 4,300 feet MSL, top unknown, temperature minus 12, light to moderate rime ice between 5,500 to 8,000 feet MSL.

UA /OV IRW090064/TM 1522/FL080/TP C172/SK SCT090-TOPUNKN/WX FV05SM HZ/TA M04/WV 24040KT/TB LGT/RM IN CLR

Pilot Weather Report, 90 degrees and 64 nautical miles from Will Rogers VORTAC, Oklahoma City, Oklahoma, 1522 UTC, 8,000 feet MSL, Cessna 172, base of a scattered layer 9,000 feet MSL, top unknown, flight visibility 5 statute miles, haze, temperature minus 4, wind 240 degrees at 40 knots, light turbulence, remarks, in clear.

UA /OV KLIT-KFSM/TM 0310/FL100/TP BE36/SK SCT070-TOP110/TA M03/WV 25015KT

Pilot Weather Report, between Little Rock and Fort Smith, Arkansas, 0310 UTC at 10,000 feet MSL. Beech 36, base of a scattered layer at 7,000 feet MSL, top 11,000 feet MSL, temperature minus 3, wind 250 degrees at 15 knots.

UA /OV KAEG/TM 1845/FL UNKN/TP UNKN /RM TIJERAS PASS CLSD DUE TO FG AND LOW CLDS UNA VFR RTN KAEG.

Pilot Weather Report, over Double Eagle II Airport, Albuquerque, New Mexico, 1845 UTC, remarks, Tijeras Pass closed due to fog and low clouds, unable to fly VFR, returned to Double Eagle II Airport.

UA /OV ENA14520/TM 2200/FL310/TP B737/TB MOD CAT 350-390.

Pilot Weather Report, 145 degrees at 20 nautical miles from Kenai, Alaska, at 2200 UTC, at flight level 310, Boeing 737, moderate clear air turbulence between 35,000 and 39,000 feet MSL.

3.3 Radar Weather Report (SD/ROB)

A Radar Weather Report (SD/ROB) contains information about precipitation observed by weather radar. This is a textual product derived from the WSR-88D NEXRAD radar without human intervention. The resolution of this textual product is very coarse, up to 80 minutes old, and should only be used if no other radar information is available.

Figure 3-11. Radar Weather Report (SD/ROB) Coding Format

3.3.1 Format

Reports are transmitted hourly from WSR-88D Weather Radar sites (see figure 3-15). The SD/ROB format is presented in Figure 3-8.

3.3.1.1 Location Identifier

The location identifier is reported as the three-letter International Air Transport Association (IATA) code.

Example:

TLX Oklahoma City Twin Lakes, Oklahoma

3.3.1.2 Time

The time of the observation is reported in four-digits Universal Time Coordinated (UTC).

Example:

1935 1935 UTC

3.3.1.3 Configuration

Three types of configurations can be reported: CELL, LN (line), and AREA. Multiple configurations can be reported within one Weather Radar Report.

A CELL is a single, isolated convective echo.

A LN (line) is a convective echo that meets the following criteria:

  • Contains heavy or greater intensity precipitation
  • Is at least 30 miles long
  • Length is at least four times greater than width
  • Contains at least 25 percent coverage

An AREA is a group of echoes of similar type, not classified as a line.

Figure 3-12 illustrates the three configurations that can be reported in a Weather Radar Report.

Figure 3-12. Radar Weather Report (SD/ROB) Configurations

3.3.1.4 Coverage

Coverage of precipitation is coded in single digits representing tenths of coverage.

For echo configurations containing multiple precipitation types, coverage is coded for each type. Total coverage is obtained by adding the individual values.

Examples:

2TRW+4R 2/10 coverage TRW+, 4/10 coverage R, 6/10 total coverage

3R6S- 3/10 coverage R, 6/10 coverage S-, 9/10 total coverage

3.3.1.5 Precipitation Type

Precipitation type is determined by computer model.

Reportable types are:

Rain (R)

Rain shower (RW)

Snow (S)

Snow shower (SW)

Thunderstorm (T)

Multiple precipitation types can be reported within a configuration.

3.3.1.6 Precipitation Intensity

Four precipitation intensities can be reported as shown in table 3-11.

Table 3-11. SD/ROB Reportable Intensities

Symbol

Intensity

dBZ

-

Light

0-29

(no entry)

Moderate

30-40

+

Heavy

41-45

++

Heavy

46-49

X

Extreme

50-56

XX

Extreme

57 or more

Examples:

7R- 7/10 coverage of light rain

3R-6S 3/10 coverage light rain, 6/10 coverage moderate snow, 9/10 total coverage

2TRWX4R- 2/10 coverage thunderstorms, extreme rain showers, 4/10 coverage light rain, 6/10 total coverage

3.3.1.7 Location

An area is coded with two end points and a width that defines a rectangle. Each end point is defined by an azimuth and range (AZRAN).

A line is also coded with two end points and a width that defines a rectangle. Each end point is defined by an AZRAN.

A cell is coded as a single point with a diameter (D). This point is defined by an AZRAN.

Figure 3-13. SD/ROB AREA, Line (LN), and CELL Location Examples

The “+” denotes the radar location.

3.3.1.8 Maximum Top

Maximum top (MT or MTS) denotes the altitude and location of the top of the highest precipitation echo.

All radar heights are estimates and assume standard atmosphere conditions and, thus, standard radar wave propagation. MT denotes radar data alone was used to determine the maximum top. MTS denotes both satellite and radar data were used to estimate the maximum top.

The maximum top is coded as a three-digit number in hundreds of feet MSL. Location is coded as an azimuth and range (AZRAN) relative to the radar site. If echo tops are uniform in altitude, the letter “U” precedes the altitude with no AZRAN provided.

Examples:

MT 150 19/32 Maximum top 15,000 feet MSL at 19 degrees, 32 nautical miles

MT 340 182/98 Maximum top 34,000 feet MSL at 182 degrees, 98 nautical miles

MTS 520 5/121 Maximum top with satellite data 52,000 feet MSL at 5 degrees, 121 nautical miles

3.3.1.9 Cell Movement

Cell movement is the average motion of all the cells within a configuration. It is coded in the following format: the cell movement group is indicated by the letter C followed by four digits. The first two digits represent the direction the cell(s) is (are) moving from in tens of degrees referenced to true north. The last two digits represent the speed of the configuration in knots.

Movement of areas and lines is not coded.

Examples:

C0209 Cell movement from 20 degrees at 9 knots

C2043 Cell movement from 200 degrees at 43 knots

C3616 Cell movement from 360 degrees at 16 knots

3.3.1.10 Remarks

Remarks contain information about the radar’s status and type of report. Currently, all weather radar reports are automated.

Table 3-12. Weather Radar Report Remarks and Meaning

REMARK

MEANING

PPINE

Equipment normal and operating, but no echoes observed

PPINA

Observation not available

PPIOM

Radar out for maintenance

AUTO

Report derived from an automated weather radar

3.3.1.11 Digital Section

The information contained in the digital section is used primarily to create the Radar Summary Chart. However, with the proper grid overlay chart for the corresponding radar site, the digital section code can also be used to determine precipitation location and intensity. (See Figure 3-14 for an example of a digital code plotted from the Oklahoma City, Oklahoma, Weather Radar Report.)

Each digit represents the maximum precipitation intensity found within a grid box as determined by the weather radar. Light intensity is denoted by a 1, 2 is for moderate, 3 and 4 is for heavy, 5 and 6 is used for extreme precipitation. These digits were once commonly referred to as VIP levels because precipitation intensity, and therefore the digit, was derived using a video integrator processor (VIP). Whereas the old WSR-57 and WSR-74 weather radar video integrator processors displayed six data levels, the WSR-88D weather radar displays sixteen data levels. The data levels are still converted back to six levels for use in the Radar Weather Report. To avoid confusion, the term VIP should no longer be used to describe precipitation intensity. For example, if a grid box is coded with the number 2, it would be described as “moderate” precipitation,” not “VIP 2” or “level 2” precipitation.

A grid box is identified by two letters. The first represents the row in which the box is found and the second letter represents the column. For example MO1 identifies the box located in row M and column O as containing light precipitation. A code of MO1234 indicates precipitation in four consecutive boxes in the same row. Working from left to right: box MO = 1, box MP = 2, MQ = 3, and box MR = 4.

A Weather Radar Report contains data about precipitation echoes only. It does not contain information about important non-precipitation echoes such as clouds, fronts, dust, etc., which can be detected by weather radar under certain circumstances.

Figure 3-14. SD/ROB Digital Section Information Plotted on a PPI Grid Overlay Example

(See Table 3-11 for Intensity Level Codes 1 through 6.)

3.3.2 Examples

GRB 1135 AREA 4TRW+ 9/101 133/76 54W MT 310 45/47 C2428 AUTO

Green Bay, Wisconsin, automated Radar Weather Report at 1135 UTC. An area of echoes, 4/10 coverage, contained thunderstorms and heavy rain showers. Area is defined by points (referenced from GRB radar site) at 9 degrees, 101 nautical miles and 133 degrees, 76 nautical miles. These points, plotted on a map and connected with a straight line, define the center line of the echo pattern. The width of the area was 54 nautical miles; i.e., 27 nautical miles either side of the center line. Maximum top was 31,000 feet MSL located at 45 degrees and 47 nautical miles from Green Bay. Cell movement was from 240 degrees at 28 knots.

ICT 1935 LN 9TRWX 274/84 216/93 22W MTS 440 260/48 C2131 AUTO

Wichita, Kansas, automated Radar Weather Report at 1935 UTC. A line of echoes, 9/10 coverage, contained thunderstorm with intense rain showers. The center of the line extended

from 274 degrees, 84 nautical miles to 216 degrees, 93 nautical miles. The line was 22 nautical miles wide.

To display graphically, plot the center points on a map and connect the points with a straight line; then plot the width. Since the thunderstorm line was 22 nautical miles wide, it extended 11 nautical miles either side of your plotted line.

The maximum top is 44,000 feet MSL at 260 degrees, 48 nautical miles from Wichita. Cell movement was from 210 degrees at 31 knots.

GGW 1135 AREA 3S- 95/129 154/81 34W MT 100 130/49 0805 AUTO

Glasgow, Montana, automated Radar Weather Report at 1135 UTC. An area, 3/10 coverage, of light snow. The area’s centerline extended from points at 95 degrees, 129 nautical miles to 154 degrees, 81 nautical miles from Glasgow. The area was 34 nautical miles wide. The maximum top was 10,000 feet MSL, at 130 degrees, 49 nautical miles from Glasgow. Cell movement was from 80 degrees at 5 knots.

JGX 2235 AREA 2TRW++6R- 67/130 308/45 106W MT 380 66/54 C2038 AUTO

Atlanta, Georgia, automated Radar Weather Report at 2235 UTC. An area of echoes, total coverage 8/10, with 2/10 of thunderstorms with very heavy rain showers and 6/10 coverage of light rain (This suggests that the thunderstorms were embedded in an area of light rain). The area was 53 nautical miles either side of the line defined by the two points, 67 degrees, 130 nautical miles and 308 degrees, 45 nautical miles from Atlanta. Maximum top was at 38,000 feet and was located on the 66 degree radial of JGX at 54 nautical miles. Cell movement was from 200 degrees at 38 knots.

HKM 0235 CELL TRW+ 19/22 D5 MT 270 18/23 C0414 AUTO

Kohala, Hawaii, automated Radar Weather Report at 0235 UTC. A cell, containing thunderstorms with very heavy rain showers, 5 miles in diameter, was located 19 degrees, 22 nautical miles from Kohala. Maximum top was 27,000 feet located at 18 degrees, 23 nautical miles from Kohala. Movement was from 40 degrees at 14 knots.

TLX 0435 PPINE AUTO

Oklahoma City, Oklahoma, automated Radar Weather Report at 0435 UTC, detected no echoes.

Figure 3-15. WSR-88D Weather Radar Network Sites