MET.TR.205 Reporting of meteorological elements

NOISE ABATEMENT PROCEDURES The noise abatement procedures are those in accordance with 7.2.6 of ICAO Doc 4444 ‘Procedures for Air Navigation Services (PANS-ATM)’.

VISIBILITY In METAR and SPECI, visibility should be reported as prevailing visibility. When the visibility is not the same in different directions and:

(a)when the lowest visibility is different from the prevailing visibility, and (1) less than 1 500 m or (2) less than 50 % of the prevailing visibility, and less than 5 000 m, the lowest visibility observed should also be reported and, when possible, its general direction in relation to the aerodrome reference point indicated by reference to one of the eight points of the compass;

(b)if the lowest visibility is observed in more than one direction, then the most operationally significant direction should be reported; and

(c)when the visibility is fluctuating rapidly, and the prevailing visibility cannot be determined, only the lowest visibility should be reported, with no indication of direction.

VISIBILITY — VALUES In local routine report and local special report, when instrumented systems are used for the measurement of visibility:

(a)if the visibility is observed from more than one location along the runway, the values representative of the touchdown zone should be reported first, followed, as necessary, by the values representative of the mid-point and stop-end of the runway, and the locations for which these values are representative should be indicated; and

(b)when there is more than one runway in use and the visibility is observed related to these runways, the available visibility values for each runway should be reported, and the runways to which the values refer should be indicated.

RUNWAY VISUAL RANGE (RVR) — TOUCHDOWN ZONE VALUES In METAR and SPECI:

(a)only the value representative of the touchdown zone should be reported and no indication of location on the runway should be included; and

(b)where there is more than one runway available for landing, touchdown zone RVR values should be included for all such runways, up to a maximum of four, and the runways to which the values refer should be indicated.

RUNWAY VISUAL RANGE (RVR) — THRESHOLD LIMITS

(a)50 m should be considered the lower limit, and 2 000 m the upper limit for RVR.

(b)Beyond these limits, local routine report, local special report, METAR and SPECI should merely indicate that the RVR is less than 50 or more than 2 000 m.

RUNWAY VISUAL RANGE (RVR) — VALUES FOR METAR AND SPECI

(a)When instrumented systems are used for the assessment of RVR, the variations in RVR during the 10-minute period immediately preceding the observation should be included if the RVR values during the 10-minute period have shown a distinct tendency, such that the mean during the first 5 minutes varies by 100 m or more from the mean during the second 5 minutes of the period.

(b)When the variation of the RVR values shows an upward or downward tendency, this should be indicated by the abbreviation ‘U’ or ‘D’, respectively. In cases when actual fluctuations during the 10-minute period show no distinct tendency, this should be indicated using the abbreviation ‘N’.

(c)When indications of tendency are not available, no abbreviations should be included.

RUNWAY VISUAL RANGE (RVR) — VALUES REPRESENTATION

(a)RVR assessments should be representative of:

(1)the touchdown zone of the runway intended for Category I instrument approach and landing operations;

(2)the touchdown zone and the mid-point of the runway intended for Category II instrument approach and landing operations; and

(3)the touchdown zone, mid-point and stop-end of the runway intended for Category III instrument approach and landing operations.

(b)Where RVR is determined by human observers, it should be reported to the appropriate local ATS units, whenever there is a change in the value to be reported in accordance with the reporting scale.

(c)The transmission of such reports should normally be completed within 15 seconds after the termination of the observation.

PRESENT WEATHER PHENOMENA — AUTOMATIC OBSERVING SYSTEM In local routine report, local special report, METAR and SPECI reported by an automatic observing system, the following types of present weather phenomena should be reported, using their respective abbreviations and relevant criteria, as appropriate:

(a)Precipitation:

(1)drizzle (DZ);

(2)rain (RA);

(3)snow (SN); and

(4)Unidentified precipitation (UP)

(b)Obscurations (hydrometeors);

(1)Fog (FG): reported when visibility is less than 1 000 m ;

(2)Mist (BR): reported when visibility is at least 1 000 m, but not more than 5 000 m;

(c)Obscurations (lithometeors). Haze (HZ) should be used when the obscuration consists predominantly of lithometeors and the visibility is 5 000 m or less; and

(d)Temporary failure of system/sensor: the present weather should be replaced by ‘//’ when it cannot be observed due to a temporary failure of the system/sensor.

PRESENT WEATHER PHENOMENA — SEMI-AUTOMATIC OBSERVING SYSTEM In local routine report, local special report, METAR and SPECI reported by a semi-automatic observing system, the following types of present weather phenomena should be reported, using their respective abbreviations and relevant criteria, as appropriate:

(a)Precipitation:

(1)drizzle (DZ);

(2)rain (RA);

(3)snow (SN);

(4)snow grains (SG);

(5)ice pellets (PL);

(6)hail (GR): reported when the diameter of the largest hailstones is 5 mm or more;

(7)small hail and/or snow pellets (GS): reported when the diameter of the largest hailstones is less than 5 mm.

(b)Obscurations (hydrometeors):

(1)fog (FG): reported when visibility is less than 1 000 m, except when qualified by ‘MI’, ‘BC’, ‘PR’ or ‘VC’.

(2)mist (BR): reported when visibility is at least 1 000 m, but not more than 5 000 m;

(c)Obscurations (lithometeors) The following should be used only when the obscuration consists predominantly of lithometeors and the visibility is 5 000 m or less, except ‘SA’ when qualified by ‘DR’ and volcanic ash:

(1)sand (SA);

(2)dust (widespread) (DU);

(3)haze (HZ);

(4)smoke (FU); and

(5)volcanic ash (VA).

(d)Other phenomena:

(1)dust/sand whirls (dust devils) (PO);

(2)squall (SQ);

(3)funnel cloud (tornado or waterspout) (FC);

(4)dust storm (DS);

(5)sandstorm (SS).

PRESENT WEATHER PHENOMENA — UNIDENTIFIED PRECIPITATION (UP) In automated local routine report, local special report, METAR and SPECI, in addition to drizzle (DZ), rain (RA) and snow (SN), the abbreviation ‘UP’ should be used for unidentified precipitation when the type of precipitation cannot be identified by the automatic observing system.

PRESENT WEATHER PHENOMENA — CHARACTERISTICS

(a)In local routine report, local special report, METAR and SPECI, only when reported by a semi-automatic observing system, the following characteristics of present weather phenomena, as necessary, should be reported using their respective abbreviations and relevant criteria, as appropriate:

(1)Shower (SH): used to report showers. Showers observed in the vicinity of the aerodrome should be reported as ‘VCSH’ without qualification regarding type or intensity of precipitation.

(2)Blowing (BL): used with types of present weather phenomena raised by the wind to a height of 6 ft (2 m) or more above the ground.

(3)Low drifting (DR): used with types of present weather phenomena raised by the wind to less than 6 ft (2 m) above ground level.

(4)Shallow (MI): less than 6 ft (2 m) above ground level.

(5)Patches (BC): fog patches randomly covering the aerodrome.

(6)Partial (PR): a substantial part of the aerodrome covered by fog while the remainder is clear.

(b)In automated local routine report, local special report, METAR and SPECI, when showers (SH) referred to above cannot be determined based upon a method that takes account of the presence of convective cloud, the precipitation should not be characterised by ‘SH’.

PRESENT WEATHER PHENOMENA — INTENSITY In local routine report, local special report, METAR and SPECI, the relevant intensity or, as appropriate, the proximity to the aerodrome of the reported present weather phenomena should be indicated as follows:

Used with types of present weather phenomena. Light intensity should be indicated only for precipitation. Vicinity (VC) Between approximately 8 and 16 km of the aerodrome reference point and used only in METAR and SPECI with present weather when not reported under AMC1 MET.TR.205(d)(3) and MET.TR.205(d)(3).

PRESENT WEATHER PHENOMENA — TS LIGHTNING DETECTION EQUIPMENT

(a)At aerodromes with human observers, lightning detection equipment may supplement human observations.

(b)For aerodromes with automatic observing systems, guidance on the use of lightning detection equipment intended for thunderstorm reporting is given in ICAO Doc 9837 ‘Manual on Automatic Meteorological Observing Systems at Aerodromes'.

CLOUD In local routine report, local special report, METAR and SPECI:

(a)the cloud amount should be reported using the abbreviations ‘FEW’ (1 to 2 oktas), ‘SCT’ (3 to 4 oktas), ‘BKN’ (5 to7 oktas) or ‘OVC’ (8 oktas);

(b)cumulonimbus clouds and towering cumulus clouds should be indicated as ‘CB’ and ‘TCU’, respectively;

(c)the vertical visibility should be reported in steps of 100 ft (30 m) up to 2 000 ft (600 m);

(d)if there are no clouds of operational significance and no restriction on vertical visibility and the abbreviation ‘CAVOK’ is not appropriate, the abbreviation ‘NSC’ should be used;

(e)when several layers or masses of cloud of operational significance are observed, their amount and height of cloud base should be reported in increasing order of the height of cloud base, and in accordance with the following criteria:

(1)the lowest layer or mass, regardless of the amount to be reported as FEW, SCT, BKN or OVC, as appropriate;

(2)the next layer or mass, covering more than 2/8 to be reported as SCT, BKN or OVC, as appropriate;

(3)the next higher layer or mass, covering more than 4/8 to be reported as BKN or OVC, as appropriate; and

(4)cumulonimbus and/or towering cumulus clouds, whenever observed and not reported in (1) to (3).

(f)when the cloud base is diffuse or ragged or fluctuating rapidly, the minimum height of cloud base or cloud fragments, should be reported; and

(g)when an individual layer (mass) of cloud is composed of cumulonimbus and towering cumulus clouds with a common cloud base, the type of cloud should be reported as cumulonimbus only.

CLOUD — AUTOMATIC OBSERVING SYSTEM When an automatic observing system is used to report local routine report, local special report, METAR and SPECI:

(a)when the cloud type cannot be observed, the cloud type in each cloud group should be replaced by ‘///’;

(b)when no clouds are detected, it should be indicated by using the abbreviation ‘NCD’;

(c)when cumulonimbus clouds or towering cumulus clouds are detected and the cloud amount and/or the height of cloud base cannot be observed, the cloud amount and/or the height of cloud base should be replaced by ‘///’; and

(d)when the sky is obscured and the value of the vertical visibility cannot be determined due to a temporary failure of the system/sensor, the vertical visibility should be replaced by ‘///’.

CLOUD — HEIGHT OF CLOUD BASE At aerodromes where low-visibility procedures are established for approach and landing, as agreed between the aeronautical meteorological station and the appropriate ATS unit, in local routine report and local special report, the height of cloud base should be reported in steps of 50 ft up to and including 300 ft and in steps of 100 ft between 300 ft and 10 000 ft, and the vertical visibility in steps of 50 ft up to and including 300 ft and in steps of 100 ft between 300 ft and 2 000 ft.